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Wikipedia

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The possibility of life on Mars is a subject of interest in astrobiology due to the planet's proximity and similarities to Earth. To date, no proof of past or present life has been found on Mars. Cumulative evidence suggests that during the ancient Noachian time period, the surface environment of Mars had liquid water and may have been habitable for microorganisms, but habitable conditions do not necessarily indicate life.

Scientific searches for evidence of life began in the 19th century and continue today via telescopic investigations and deployed probes, searching for water, chemical biosignatures in the soil and rocks at the planet's surface, and biomarker gases in the atmosphere.

Mars is of particular interest for the study of the origins of life because of its similarity to the early Earth. This is especially true since Mars has a cold climate and lacks plate tectonics or continental drift, so it has remained almost unchanged since the end of the Hesperian period. At least two-thirds of Mars's surface is more than 3.5 billion years old, and it could have been habitable since 4.48 billion years ago, 500 million years before the earliest known Earth lifeforms; Mars may thus hold the best record of the prebiotic conditions leading to life, even if life does not or has never existed there.

Following the confirmation of the past existence of surface liquid water, the Curiosity, Perseverance and Opportunity rovers started searching for evidence of past life, including a past biosphere based on autotrophic, chemotrophic, or chemolithoautotrophic microorganisms, as well as ancient water, including fluvio-lacustrine environments ( plains related to ancient rivers or lakes) that may have been habitable. The search for evidence of habitability, taphonomy (related to fossils), and organic compounds on Mars is now a primary objective for space agencies.

The findings of organic compounds inside sedimentary rocks and of boron on Mars are of interest as they are precursors for prebiotic chemistry. Such findings, along with previous discoveries that liquid water was clearly present on ancient Mars, further supports the possible early habitability of Gale Crater on Mars. Currently, the surface of Mars is bathed with ionizing radiation, and Martian soil is rich in perchlorates toxic to microorganisms. Therefore, the consensus is that if life exists-or existed-on Mars, it could be found or is best preserved in the subsurface, away from present-day harsh surface processes.

In June 2018, NASA announced the detection of seasonal variation of methane levels on Mars. Methane could be produced by microorganisms or by geological means. The European ExoMars Trace Gas Orbiter started mapping the atmospheric methane in April 2018, and the 2022 ExoMars rover Rosalind Franklin was planned to drill and analyze subsurface samples before the programme's indefinite suspension, while the NASA Mars 2020 rover Perseverance, having landed successfully, will cache dozens of drill samples for their potential transport to Earth laboratories in the late 2020s or 2030s. As of February 8, 2021, an updated status of studies considering the possible detection of lifeforms on Venus (via phosphine) and Mars (via methane) was reported.

Mars's polar ice caps were discovered in the mid-17th century.[citation needed ] In the late 18th century, William Herschel proved they grow and shrink alternately, in the summer and winter of each hemisphere. By the mid-19th century, astronomers knew that Mars had certain other similarities to Earth, for example that the length of a day on Mars was almost the same as a day on Earth. They also knew that its axial tilt was similar to Earth's, which meant it experienced seasons just as Earth does-but of nearly double the length owing to its much longer year. These observations led to increasing speculation that the darker albedo features were water and the brighter ones were land, whence followed speculation on whether Mars may be inhabited by some form of life.

In 1854, William Whewell, a fellow of Trinity College, Cambridge, theorized that Mars had seas, land and possibly life forms. Speculation about life on Mars exploded in the late 19th century, following telescopic observation by some observers of apparent Martian canals-which were later found to be optical illusions. Despite this, in 1895, American astronomer Percival Lowell published his book Mars, followed by Mars and its Canals in 1906, proposing that the canals were the work of a long-gone civilization. This idea led British writer H. G. Wells to write The War of the Worlds in 1897, telling of an invasion by aliens from Mars who were fleeing the planet's desiccation.

Spectroscopic analysis of Mars's atmosphere began in earnest in 1894, when U.S. astronomer William Wallace Campbell showed that neither water nor oxygen were present in the Martian atmosphere. The influential observer Eugène Antoniadi used the 83-cm (32.6 inch) aperture telescope at Meudon Observatory at the 1909 opposition of Mars and saw no canals, the outstanding photos of Mars taken at the new Baillaud dome at the Pic du Midi observatory also brought formal discredit to the Martian canals theory in 1909, and the notion of canals began to fall out of favor.

Chemical, physical, geological, and geographic attributes shape the environments on Mars. Isolated measurements of these factors may be insufficient to deem an environment habitable, but the sum of measurements can help predict locations with greater or lesser habitability potential. The two current ecological approaches for predicting the potential habitability of the Martian surface use 19 or 20 environmental factors, with an emphasis on water availability, temperature, the presence of nutrients, an energy source, and protection from solar ultraviolet and galactic cosmic radiation.

Scientists do not know the minimum number of parameters for determination of habitability potential, but they are certain it is greater than one or two of the factors in the table below. Similarly, for each group of parameters, the habitability threshold for each is to be determined. Laboratory simulations show that whenever multiple lethal factors are combined, the survival rates plummet quickly. There are no full-Mars simulations published yet that include all of the biocidal factors combined. Furthermore, the possibility of Martian life having a far different biochemistry and habitability requirements than the terrestrial biosphere is an open question. A common hypothesis is methanogenic Martian life, and while such organisms exist on Earth too, they are exceptionally rare and cannot survive in the majority of terrestrial environments that contain oxygen.

Chemical environment

Nutrients:

C, H, N, O, P, S, essential metals, essential micronutrients

Fixed nitrogen

Availability/mineralogy

Toxin abundances and lethality:

Heavy metals (e.g., Zn, Ni, Cu, Cr, As, Cd, etc., some essential, but toxic at high levels)

Globally distributed oxidizing soils

Conducive
physical conditions

Temperature

Extreme diurnal temperature fluctuations

Low pressure (Is there a low-pressure threshold for terrestrial anaerobes?)

Strong ultraviolet germicidal irradiation

Galactic cosmic radiation and solar particle events (long-term accumulated effects)

Climate/variability (geography, seasons, diurnal, and eventually, obliquity variations)

Substrate (soil processes, rock microenvironments, dust composition, shielding)

High concentrations in the global atmosphere

Transport (aeolian, groundwater flow, surface water, glacial)

Recent models have shown that, even with a dense atmosphere, early Mars was colder than Earth has ever been. Transiently warm conditions related to impacts or volcanism could have produced conditions favoring the formation of the late Noachian valley networks, even though the mid-late Noachian global conditions were probably icy. Local warming of the environment by volcanism and impacts would have been sporadic, but there should have been many events of water flowing at the surface of Mars. Both the mineralogical and the morphological evidence indicates a degradation of habitability from the mid Hesperian onward. The exact causes are not well understood but may be related to a combination of processes including loss of early atmosphere, or impact erosion, or both. Billions of years ago, before this degradation, the surface of Mars was apparently fairly habitable, consisted of liquid water and clement weather, though it is unknown if life existed on Mars.

Alga crater is thought to have deposits of impact glass that may have preserved ancient biosignatures, if present during the impact.[34]

The loss of the Martian magnetic field strongly affected surface environments through atmospheric loss and increased radiation; this change significantly degraded surface habitability. When there was a magnetic field, the atmosphere would have been protected from erosion by the solar wind, which would ensure the maintenance of a dense atmosphere, necessary for liquid water to exist on the surface of Mars. The loss of the atmosphere was accompanied by decreasing temperatures. Part of the liquid water inventory sublimed and was transported to the poles, while the rest became trapped in permafrost, a subsurface ice layer.

Observations on Earth and numerical modeling have shown that a crater-forming impact can result in the creation of a long-lasting hydrothermal system when ice is present in the crust. For example, a 130 km large crater could sustain an active hydrothermal system for up to 2 million years, that is, long enough for microscopic life to emerge, but unlikely to have progressed any further down the evolutionary path.

Soil and rock samples studied in 2013 by NASA's Curiosity rover's onboard instruments brought about additional information on several habitability factors. The rover team identified some of the key chemical ingredients for life in this soil, including sulfur, nitrogen, hydrogen, oxygen, phosphorus and possibly carbon, as well as clay minerals, suggesting a long-ago aqueous environment-perhaps a lake or an ancient streambed-that had neutral acidity and low salinity. On December 9, 2013, NASA reported that, based on evidence from Curiosity studying Aeolis Palus, Gale Crater contained an ancient freshwater lake which could have been a hospitable environment for microbial life. The confirmation that liquid water once flowed on Mars, the existence of nutrients, and the previous discovery of a past magnetic field that protected the planet from cosmic and solar radiation, together strongly suggest that Mars could have had the environmental factors to support life. The assessment of past habitability is not in itself evidence that Martian life has ever actually existed. If it did, it was probably microbial, existing communally in fluids or on sediments, either free-living or as biofilms, respectively. The exploration of terrestrial analogues provide clues as to how and where best look for signs of life on Mars.

Impactite, shown to preserve signs of life on Earth, was discovered on Mars and could contain signs of ancient life, if life ever existed on the planet.

On June 7, 2018, NASA announced that the Curiosity rover had discovered organic molecules in sedimentary rocks dating to three billion years old. The detection of organic molecules in rocks indicate that some of the building blocks for life were present.

Conceivably, if life exists (or existed) on Mars, evidence of life could be found, or is best preserved, in the subsurface, away from present-day harsh surface conditions. Present-day life on Mars, or its biosignatures, could occur kilometers below the surface, or in subsurface geothermal hot spots, or it could occur a few meters below the surface. The permafrost layer on Mars is only a couple of centimeters below the surface, and salty brines can be liquid a few centimeters below that but not far down. Water is close to its boiling point even at the deepest points in the Hellas basin, and so cannot remain liquid for long on the surface of Mars in its present state, except after a sudden release of underground water.

So far, NASA has pursued a "follow the water" strategy on Mars and has not searched for biosignatures for life there directly since the Viking missions. The consensus by astrobiologists is that it may be necessary to access the Martian subsurface to find currently habitable environments.

In 1965, the Mariner 4 probe discovered that Mars had no global magnetic field that would protect the planet from potentially life-threatening cosmic radiation and solar radiation; observations made in the late 1990s by the Mars Global Surveyor confirmed this discovery. Scientists speculate that the lack of magnetic shielding helped the solar wind blow away much of Mars's atmosphere over the course of several billion years. As a result, the planet has been vulnerable to radiation from space for about 4 billion years.

Recent in-situ data from Curiosity rover indicates that ionizing radiation from galactic cosmic rays (GCR) and solar particle events (SPE) may not be a limiting factor in habitability assessments for present-day surface life on Mars. The level of 76 mGy per year measured by Curiosity is similar to levels inside the ISS.

Curiosity rover measured ionizing radiation levels of 76 mGy per year. This level of ionizing radiation is sterilizing for dormant life on the surface of Mars. It varies considerably in habitability depending on its orbital eccentricity and the tilt of its axis. If the surface life has been reanimated as recently as 450,000 years ago, then rovers on Mars could find dormant but still viable life at a depth of one meter below the surface, according to an estimate. Even the hardiest cells known could not possibly survive the cosmic radiation near the surface of Mars since Mars lost its protective magnetosphere and atmosphere. After mapping cosmic radiation levels at various depths on Mars, researchers have concluded that over time, any life within the first several meters of the planet's surface would be killed by lethal doses of cosmic radiation. The team calculated that the cumulative damage to DNA and RNA by cosmic radiation would limit retrieving viable dormant cells on Mars to depths greater than 7.5 meters below the planet's surface. Even the most radiation-tolerant terrestrial bacteria would survive in dormant spore state only 18,000 years at the surface; at 2 meters-the greatest depth at which the ExoMars rover will be capable of reaching-survival time would be 90,000 to half a million years, depending on the type of rock.

Data collected by the Radiation assessment detector (RAD) instrument on board the Curiosity rover revealed that the absorbed dose measured is 76 mGy/year at the surface, and that " ionizing radiation strongly influences chemical compositions and structures, especially for water, salts, and redox-sensitive components such as organic molecules." Regardless of the source of Martian organic compounds (meteoric, geological, or biological), its carbon bonds are susceptible to breaking and reconfiguring with surrounding elements by ionizing charged particle radiation. These improved subsurface radiation estimates give insight into the potential for the preservation of possible organic biosignatures as a function of depth as well as survival times of possible microbial or bacterial life forms left dormant beneath the surface. The report concludes that the in situ "surface measurements-and subsurface estimates-constrain the preservation window for Martian organic matter following exhumation and exposure to ionizing radiation in the top few meters of the Martian surface."

In September 2017, NASA reported radiation levels on the surface of the planet Mars were temporarily doubled and were associated with an aurora 25 times brighter than any observed earlier, due to a major, and unexpected, solar storm in the middle of the month.

On UV radiation, a 2014 report concludes that "[T]he Martian UV radiation environment is rapidly lethal to unshielded microbes but can be attenuated by global dust storms and shielded completely by < 1 mm of regolith or by other organisms." In addition, laboratory research published in July 2017 demonstrated that UV irradiated perchlorates cause a 10.8-fold increase in cell death when compared to cells exposed to UV radiation after 60 seconds of exposure. The penetration depth of UV radiation into soils is in the sub-millimeter to millimeter range and depends on the properties of the soil.

The Martian regolith is known to contain a maximum of 0.5% (w/v) perchlorate (ClO ₄−) that is toxic for most living organisms, but since they drastically lower the freezing point of water and a few extremophiles can use it as an energy source (see Perchlorates - Biology) and grow at concentrations of up to 30% (w/v) sodium perchlorate by physiologically adapting to increasing perchlorate concentrations, it has prompted speculation of what their influence would be on habitability.

Research published in July 2017 shows that when irradiated with a simulated Martian UV flux, perchlorates become even more lethal to bacteria ( bactericide). Even dormant spores lost viability within minutes. In addition, two other compounds of the Martian surface, iron oxides and hydrogen peroxide, act in synergy with irradiated perchlorates to cause a 10.8-fold increase in cell death when compared to cells exposed to UV radiation after 60 seconds of exposure. It was also found that abraded silicates (quartz and basalt) lead to the formation of toxic reactive oxygen species. The researchers concluded that "the surface of Mars is lethal to vegetative cells and renders much of the surface and near-surface regions uninhabitable." This research demonstrates that the present-day surface is more uninhabitable than previously thought, and reinforces the notion to inspect at least a few meters into the ground to ensure the levels of radiation would be relatively low.

However, researcher Kennda Lynch discovered the first-known instance of a habitat containing perchlorates and perchlorates-reducing bacteria in an analog environment: a paleolake in Pilot Valley, Great Salt Lake Desert, Utah. She has been studying the biosignatures of these microbes, and is hoping that the Mars Perseverance rover will find matching biosignatures at its Jezero Crater site.

Recurrent slope lineae (RSL) features form on Sun-facing slopes at times of the year when the local temperatures reach above the melting point for ice. The streaks grow in spring, widen in late summer and then fade away in autumn. This is hard to model in any other way except as involving liquid water in some form, though the streaks themselves are thought to be a secondary effect and not a direct indication of the dampness of the regolith. Although these features are now confirmed to involve liquid water in some form, the water could be either too cold or too salty for life. At present they are treated as potentially habitable, as "Uncertain Regions, to be treated as Special Regions".). They were suspected as involving flowing brines back then.

The thermodynamic availability of water ( water activity) strictly limits microbial propagation on Earth, particularly in hypersaline environments, and there are indications that the brine ionic strength is a barrier to the habitability of Mars. Experiments show that high ionic strength, driven to extremes on Mars by the ubiquitous occurrence of divalent ions, "renders these environments uninhabitable despite the presence of biologically available water."

After carbon, nitrogen is arguably the most important element needed for life. Thus, measurements of nitrate over the range of 0.1% to 5% are required to address the question of its occurrence and distribution. There is nitrogen (as N ₂) in the atmosphere at low levels, but this is not adequate to support nitrogen fixation for biological incorporation. Nitrogen in the form of nitrate could be a resource for human exploration both as a nutrient for plant growth and for use in chemical processes. On Earth, nitrates correlate with perchlorates in desert environments, and this may also be true on Mars. Nitrate is expected to be stable on Mars and to have formed by thermal shock from impact or volcanic plume lightning on ancient Mars.

On March 24, 2015, NASA reported that the SAM instrument on the Curiosity rover detected nitrates by heating surface sediments. The nitrogen in nitrate is in a "fixed" state, meaning that it is in an oxidized form that can be used by living organisms. The discovery supports the notion that ancient Mars may have been hospitable for life. It is suspected that all nitrate on Mars is a relic, with no modern contribution. Nitrate abundance ranges from non-detection to 681 ± 304 mg/kg in the samples examined until late 2017. Modeling indicates that the transient condensed water films on the surface should be transported to lower depths (≈10 m) potentially transporting nitrates, where subsurface microorganisms could thrive.

In contrast, phosphate, one of the chemical nutrients thought to be essential for life, is readily available on Mars.

Further complicating estimates of the habitability of the Martian surface is the fact that very little is known about the growth of microorganisms at pressures close to those on the surface of Mars. Some teams determined that some bacteria may be capable of cellular replication down to 25 mbar, but that is still above the atmospheric pressures found on Mars (range 1-14 mbar). In another study, twenty-six strains of bacteria were chosen based on their recovery from spacecraft assembly facilities, and only Serratia liquefaciens strain ATCC 27592 exhibited growth at 7 mbar, 0 °C, and CO ₂-enriched anoxic atmospheres.

Liquid water is a necessary but not sufficient condition for life as humans know it, as habitability is a function of a multitude of environmental parameters. Liquid water cannot exist on the surface of Mars except at the lowest elevations for minutes or hours. Liquid water does not appear at the surface itself, but it could form in minuscule amounts around dust particles in snow heated by the Sun.[unreliable source? ] Also, the ancient equatorial ice sheets beneath the ground may slowly sublimate or melt, accessible from the surface via caves.

Water on Mars exists almost exclusively as water ice, located in the Martian polar ice caps and under the shallow Martian surface even at more temperate latitudes. A small amount of water vapor is present in the atmosphere. There are no bodies of liquid water on the Martian surface because its atmospheric pressure at the surface averages 600 pascals (0.087 psi)-about 0.6% of Earth's mean sea level pressure-and because the temperature is far too low, (210 K (−63 °C)) leading to immediate freezing. Despite this, about 3.8 billion years ago, there was a denser atmosphere, higher temperature, and vast amounts of liquid water flowed on the surface, including large oceans.

A series of artist's conceptions of past water coverage on Mars

Mars SouthPole
Site of Subglacial Water
(July 25, 2018)

It has been estimated that the primordial oceans on Mars would have covered between 36% and 75% of the planet. On November 22, 2016, NASA reported finding a large amount of underground ice in the Utopia Planitia region of Mars. The volume of water detected has been estimated to be equivalent to the volume of water in Lake Superior. Analysis of Martian sandstones, using data obtained from orbital spectrometry, suggests that the waters that previously existed on the surface of Mars would have had too high a salinity to support most Earth-like life. Tosca et al. found that the Martian water in the locations they studied all had water activity, a w ≤ 0.78 to 0.86-a level fatal to most Terrestrial life. Haloarchaea, however, are able to live in hypersaline solutions, up to the saturation point.

In June 2000, possible evidence for current liquid water flowing at the surface of Mars was discovered in the form of flood-like gullies. Additional similar images were published in 2006, taken by the Mars Global Surveyor, that suggested that water occasionally flows on the surface of Mars. The images showed changes in steep crater walls and sediment deposits, providing the strongest evidence yet that water coursed through them as recently as several years ago.

There is disagreement in the scientific community as to whether or not the recent gully streaks were formed by liquid water. Some suggest the flows were merely dry sand flows. Others suggest it may be liquid brine near the surface, but the exact source of the water and the mechanism behind its motion are not understood.

In July 2018, scientists reported the discovery of a subglacial lake on Mars, 1.5 km (0.93 mi) below the southern polar ice cap, and extending sideways about 20 km (12 mi), the first known stable body of water on the planet. The lake was discovered using the MARSIS radar on board the Mars Express orbiter, and the profiles were collected between May 2012 and December 2015. The lake is centered at 193°E, 81°S, a flat area that does not exhibit any peculiar topographic characteristics but is surrounded by higher ground, except on its eastern side, where there is a depression.

The silica-rich patch discovered by Spirit rover

In May 2007, the Spirit rover disturbed a patch of ground with its inoperative wheel, uncovering an area 90% rich in silica. The feature is reminiscent of the effect of hot spring water or steam coming into contact with volcanic rocks. Scientists consider this as evidence of a past environment that may have been favorable for microbial life and theorize that one possible origin for the silica may have been produced by the interaction of soil with acid vapors produced by volcanic activity in the presence of water.

Based on Earth analogs, hydrothermal systems on Mars would be highly attractive for their potential for preserving organic and inorganic biosignatures. For this reason, hydrothermal deposits are regarded as important targets in the exploration for fossil evidence of ancient Martian life.

In May 2017, evidence of the earliest known life on land on Earth may have been found in 3.48-billion-year-old geyserite and other related mineral deposits (often found around hot springs and geysers) uncovered in the Pilbara Craton of Western Australia. These findings may be helpful in deciding where best to search for early signs of life on the planet Mars.

Methane (CH ₄) is chemically unstable in the current oxidizing atmosphere of Mars. It would quickly break down due to ultraviolet radiation from the Sun and chemical reactions with other gases. Therefore, a persistent presence of methane in the atmosphere may imply the existence of a source to continually replenish the gas.

Trace amounts of methane, at the level of several parts per billion (ppb), were first reported in Mars's atmosphere by a team at the NASA Goddard Space Flight Center in 2003. Large differences in the abundances were measured between observations taken in 2003 and 2006, which suggested that the methane was locally concentrated and probably seasonal. On June 7, 2018, NASA announced it has detected a seasonal variation of methane levels on Mars.

The ExoMars Trace Gas Orbiter (TGO), launched in March 2016, began on April 21, 2018, to map the concentration and sources of methane in the atmosphere, as well as its decomposition products such as formaldehyde and methanol. As of May 2019, the Trace Gas Orbiter showed that the concentration of methane is under detectable level (< 0.05 ppbv).

Curiosity detected a cyclical seasonal variation in atmospheric methane.

The principal candidates for the origin of Mars's methane include non-biological processes such as water-rock reactions, radiolysis of water, and pyrite formation, all of which produce that could then generate methane and other hydrocarbons via Fischer-Tropsch synthesis with CO and CO ₂. It has also been shown that methane could be produced by a process involving water, carbon dioxide, and the mineral olivine, which is known to be common on Mars. Although geologic sources of methane such as serpentinization are possible, the lack of current volcanism, hydrothermal activity or hotspots are not favorable for geologic methane.

Living microorganisms, such as methanogens, are another possible source, but no evidence for the presence of such organisms has been found on Mars, until June 2019 as methane was detected by the Curiosity rover. Methanogens do not require oxygen or organic nutrients, are non-photosynthetic, use hydrogen as their energy source and carbon dioxide (CO ₂) as their carbon source, so they could exist in subsurface environments on Mars. If microscopic Martian life is producing the methane, it probably resides far below the surface, where it is still warm enough for liquid water to exist.

Since the 2003 discovery of methane in the atmosphere, some scientists have been designing models and in vitro experiments testing the growth of methanogenic bacteria on simulated Martian soil, where all four methanogen strains tested produced substantial levels of methane, even in the presence of 1.0wt% perchlorate salt.

A team led by Levin suggested that both phenomena-methane production and degradation-could be accounted for by an ecology of methane-producing and methane-consuming microorganisms.

Distribution of methane in the atmosphere of Mars in the Northern Hemisphere during summer

Research at the University of Arkansas presented in June 2015 suggested that some methanogens could survive in Mars's low pressure. Rebecca Mickol found that in her laboratory, four species of methanogens survived low-pressure conditions that were similar to a subsurface liquid aquifer on Mars. The four species that she tested were Methanothermobacter wolfeii, Methanosarcina barkeri, Methanobacterium formicicum, and Methanococcus maripaludis. In June 2012, scientists reported that measuring the ratio of hydrogen and methane levels on Mars may help determine the likelihood of life on Mars. According to the scientists, "low H ₂/CH ₄ ratios (less than approximately 40)" would "indicate that life is likely present and active". The observed ratios in the lower Martian atmosphere were "approximately 10 times" higher "suggesting that biological processes may not be responsible for the observed CH ₄". The scientists suggested measuring the H ₂ and CH ₄ flux at the Martian surface for a more accurate assessment. Other scientists have recently reported methods of detecting hydrogen and methane in extraterrestrial atmospheres.

Even if rover missions determine that microscopic Martian life is the seasonal source of the methane, the life forms probably reside far below the surface, outside of the rover's reach.

In February 2005, it was announced that the Planetary Fourier Spectrometer (PFS) on the European Space Agency's Mars Express Orbiter had detected traces of formaldehyde in the atmosphere of Mars. Vittorio Formisano, the director of the PFS, has speculated that the formaldehyde could be the byproduct of the oxidation of methane and, according to him, would provide evidence that Mars is either extremely geologically active or harboring colonies of microbial life. NASA scientists consider the preliminary findings well worth a follow-up but have also rejected the claims of life.

The 1970s Viking program placed two identical landers on the surface of Mars tasked to look for biosignatures of microbial life on the surface. Of the four experiments performed by each Viking lander, only the 'Labeled Release' (LR) experiment gave a positive result for metabolism, while the other three did not detect organic compounds. The LR was a specific experiment designed to test only a narrowly defined critical aspect of the theory concerning the possibility of life on Mars; therefore, the overall results were declared inconclusive. No Mars lander mission has found meaningful traces of biomolecules or biosignatures. The claim of extant microbial life on Mars is based on old data collected by the Viking landers, currently reinterpreted as sufficient evidence of life, mainly by Gilbert Levin, Joseph D. Miller, Navarro, Giorgio Bianciardi and Patricia Ann Straat.

Assessments published in December 2010 by Rafael Navarro-Gonzáles indicate that organic compounds "could have been present" in the soil analyzed by both Viking 1 and 2. The study determined that perchlorate-discovered in 2008 by Phoenix lander-can destroy organic compounds when heated, and produce chloromethane and dichloromethane as a byproduct, the identical chlorine compounds discovered by both Viking landers when they performed the same tests on Mars. Because perchlorate would have broken down any Martian organics, the question of whether or not Viking found organic compounds is still wide open.

The Labeled Release evidence was not generally accepted initially, and, to this day lacks the consensus of the scientific community.

As of 2018, there are 224 known Martian meteorites (some of which were found in several fragments). These are valuable because they are the only physical samples of Mars available to Earth-bound laboratories. Some researchers have argued that microscopic morphological features found in ALH84001 are biomorphs, however this interpretation has been highly controversial and is not supported by the majority of researchers in the field.

Seven criteria have been established for the recognition of past life within terrestrial geologic samples. Those criteria are:

1. Is the geologic context of the sample compatible with past life?

2. Is the age of the sample and its stratigraphic location compatible with possible life?

3. Does the sample contain evidence of cellular morphology and colonies?

4. Is there any evidence of biominerals showing chemical or mineral disequilibria?

5. Is there any evidence of stable isotope patterns unique to biology?

6. Are there any organic biomarkers present?

7. Are the features indigenous to the sample?

For general acceptance of past life in a geologic sample, essentially most or all of these criteria must be met. All seven criteria have not yet been met for any of the Martian samples.

An electron microscope reveals bacteria-like structures in meteorite fragment ALH84001

In 1996, the Martian meteorite ALH84001, a specimen that is much older than the majority of Martian meteorites that have been recovered so far, received considerable attention when a group of NASA scientists led by David S. McKay reported microscopic features and geochemical anomalies that they considered to be best explained by the rock having hosted Martian bacteria in the distant past. Some of these features resembled terrestrial bacteria, aside from their being much smaller than any known form of life. Much controversy arose over this claim, and ultimately all of the evidence McKay's team cited as evidence of life was found to be explainable by non-biological processes. Although the scientific community has largely rejected the claim ALH 84001 contains evidence of ancient Martian life, the controversy associated with it is now seen as a historically significant moment in the development of exobiology.

Nakhla meteorite

The Nakhla meteorite fell on Earth on June 28, 1911, on the locality of Nakhla, Alexandria, Egypt.

In 1998, a team from NASA's Johnson Space Center obtained a small sample for analysis. Researchers found preterrestrial aqueous alteration phases and objects of the size and shape consistent with Earthly fossilized nanobacteria. Analysis with gas chromatography and mass spectrometry (GC-MS) studied its high molecular weight polycyclic aromatic hydrocarbons in 2000, and NASA scientists concluded that as much as 75% of the organic compounds in Nakhla "may not be recent terrestrial contamination".

This caused additional interest in this meteorite, so in 2006, NASA managed to obtain an additional and larger sample from the London Natural History Museum. On this second sample, a large dendritic carbon content was observed. When the results and evidence were published in 2006, some independent researchers claimed that the carbon deposits are of biologic origin. It was remarked that since carbon is the fourth most abundant element in the Universe, finding it in curious patterns is not indicative or suggestive of biological origin.

The Shergotty meteorite, a 4 kilograms (8.8 lb) Martian meteorite, fell on Earth on Shergotty, India on August 25, 1865, and was retrieved by witnesses almost immediately. It is composed mostly of pyroxene and thought to have undergone preterrestrial aqueous alteration for several centuries. Certain features in its interior suggest remnants of a biofilm and its associated microbial communities.

Yamato 000593 is the second largest meteorite from Mars found on Earth. Studies suggest the Martian meteorite was formed about 1.3 billion years ago from a lava flow on Mars. An impact occurred on Mars about 12 million years ago and ejected the meteorite from the Martian surface into space. The meteorite landed on Earth in Antarctica about 50,000 years ago. The mass of the meteorite is 13.7 kg (30 lb) and it has been found to contain evidence of past water movement. At a microscopic level, spheres are found in the meteorite that are rich in carbon compared to surrounding areas that lack such spheres. The carbon-rich spheres may have been formed by biotic activity according to NASA scientists.

Organism-substrate interactions and their products are important biosignatures on Earth as they represent direct evidence of biological behaviour. It was the recovery of fossilized products of life-substrate interactions (ichnofossils) that has revealed biological activities in the early history of life on the Earth, e.g., Proterozoic burrows, Archean microborings and stromatolites. Two major ichnofossil-like structures have been reported from Mars, i.e. the stick-like structures from Vera Rubin Ridge and the microtunnels from Martian Meteorites.

Observations at Vera Rubin Ridge by the Mars Space Laboratory rover Curiosity show millimetric, elongate structures preserved in sedimentary rocks deposited in fluvio-lacustrine environments within Gale Crater. Morphometric and topologic data are unique to the stick-like structures among Martian geological features and show that ichnofossils are among the closest morphological analogues of these unique features. Nevertheless, available data cannot fully disprove two major abiotic hypotheses, that are sedimentary cracking and evaporitic crystal growth as genetic processes for the structures.

Microtunnels have been described from Martian meteorites. They consist of straight to curved microtunnels that may contain areas of enhanced carbon abundance. The morphology of the curved microtunnels is consistent with biogenic traces on Earth, including microbioerosion traces observed in basaltic glasses. Further studies are needed to confirm biogenicity.

The seasonal frosting and defrosting of the southern ice cap results in the formation of spider-like radial channels carved on 1-meter thick ice by sunlight. Then, sublimed CO ₂ - and probably water - increase pressure in their interior producing geyser-like eruptions of cold fluids often mixed with dark basaltic sand or mud. This process is rapid, observed happening in the space of a few days, weeks or months, a growth rate rather unusual in geology - especially for Mars.

A team of Hungarian scientists propose that the geysers' most visible features, dark dune spots and spider channels, may be colonies of photosynthetic Martian microorganisms, which over-winter beneath the ice cap, and as the sunlight returns to the pole during early spring, light penetrates the ice, the microorganisms photosynthesize and heat their immediate surroundings. A pocket of liquid water, which would normally evaporate instantly in the thin Martian atmosphere, is trapped around them by the overlying ice. As this ice layer thins, the microorganisms show through grey. When the layer has completely melted, the microorganisms rapidly desiccate and turn black, surrounded by a grey aureole. The Hungarian scientists believe that even a complex sublimation process is insufficient to explain the formation and evolution of the dark dune spots in space and time. Since their discovery, fiction writer Arthur C. Clarke promoted these formations as deserving of study from an astrobiological perspective.

A multinational European team suggests that if liquid water is present in the spiders' channels during their annual defrost cycle, they might provide a niche where certain microscopic life forms could have retreated and adapted while sheltered from solar radiation. A British team also considers the possibility that organic matter, microbes, or even simple plants might co-exist with these inorganic formations, especially if the mechanism includes liquid water and a geothermal energy source. They also remark that the majority of geological structures may be accounted for without invoking any organic "life on Mars" hypothesis. It has been proposed to develop the Mars Geyser Hopper lander to study the geysers up close.

Planetary protection of Mars aims to prevent biological contamination of the planet. A major goal is to preserve the planetary record of natural processes by preventing human-caused microbial introductions, also called forward contamination. There is abundant evidence as to what can happen when organisms from regions on Earth that have been isolated from one another for significant periods of time are introduced into each other's environment. Species that are constrained in one environment can thrive - often out of control - in another environment much to the detriment of the original species that were present. In some ways, this problem could be compounded if life forms from one planet were introduced into the totally alien ecology of another world.

The prime concern of hardware contaminating Mars derives from incomplete spacecraft sterilization of some hardy terrestrial bacteria ( extremophiles) despite best efforts. Hardware includes landers, crashed probes, end-of-mission disposal of hardware, and the hard landing of entry, descent, and landing systems. This has prompted research on survival rates of radiation-resistant microorganisms including the species Deinococcus radiodurans and genera Brevundimonas, Rhodococcus, and Pseudomonas under simulated Martian conditions. Results from one of these experimental irradiation experiments, combined with previous radiation modeling, indicate that Brevundimonas sp. MV.7 emplaced only 30 cm deep in Martian dust could survive the cosmic radiation for up to 100,000 years before suffering 10 ⁶ population reduction. The diurnal Mars-like cycles in temperature and relative humidity affected the viability of Deinococcus radiodurans cells quite severely. In other simulations, Deinococcus radiodurans also failed to grow under low atmospheric pressure, under 0 °C, or in the absence of oxygen.

Since the 1950s, researchers have used containers that simulate environmental conditions on Mars to determine the viability of a variety of lifeforms on Mars. Such devices, called " Mars jars" or "Mars simulation chambers", were first described and used in U.S. Air Force research in the 1950s by Hubertus Strughold, and popularized in civilian research by Joshua Lederberg and Carl Sagan.

On April 26, 2012, scientists reported that an extremophile lichen survived and showed remarkable results on the adaptation capacity of photosynthetic activity within the simulation time of 34 days under Martian conditions in the Mars Simulation Laboratory (MSL) maintained by the German Aerospace Center (DLR). The ability to survive in an environment is not the same as the ability to thrive, reproduce, and evolve in that same environment, necessitating further study.

Although numerous studies point to resistance to some of Mars conditions, they do so separately, and none has considered the full range of Martian surface conditions, including temperature, pressure, atmospheric composition, radiation, humidity, oxidizing regolith, and others, all at the same time and in combination. Laboratory simulations show that whenever multiple lethal factors are combined, the survival rates plummet quickly.

Astrobiologists funded by NASA are researching the limits of microbial life in solutions with high salt concentrations at low temperature. Any body of liquid water under the polar ice caps or underground is likely to exist under high hydrostatic pressure and have a significant salt concentration. They know that the landing site of Phoenix lander was found to be regolith cemented with water ice and salts, and the soil samples likely contained magnesium sulfate, magnesium perchlorate, sodium perchlorate, potassium perchlorate, sodium chloride and calcium carbonate. Earth bacteria capable of growth and reproduction in the presence of highly salted solutions, called halophile or "salt-lover", were tested for survival using salts commonly found on Mars and at decreasing temperatures. The species tested include , Marinococcus, Nesterenkonia, and Virgibacillus. Laboratory simulations show that whenever multiple Martian environmental factors are combined, the survival rates plummet quickly, however, halophile bacteria were grown in a lab in water solutions containing more than 25% of salts common on Mars, and starting in 2019[needs update ], the experiments will incorporate exposure to low temperature, salts, and high pressure.

On 21 February 2023, scientists reported the findings of a " dark microbiome" of unfamiliar microorganisms in the Atacama Desert in Chile, a Mars-like region of planet Earth.

Mars-1 was the first spacecraft launched to Mars in 1962, but communication was lost while en route to Mars. With Mars-2 and Mars-3 in 1971-1972, information was obtained on the nature of the surface rocks and altitude profiles of the surface density of the soil, its thermal conductivity, and thermal anomalies detected on the surface of Mars. The program found that its northern polar cap has a temperature below −110 °C (−166 °F) and that the water vapor content in the atmosphere of Mars is five thousand times less than on Earth. No signs of life were found.

Signs of life of the Mars space program AMS from orbit were not found. The descent vehicle Mars-2 crashed on landing, the descent vehicle Mars-3 launched 1.5 minutes after landing in the Ptolemaeus crater, but worked only 14.5 seconds/

Mariner 4 probe performed the first successful flyby of the planet Mars, returning the first pictures of the Martian surface in 1965. The photographs showed an arid Mars without rivers, oceans, or any signs of life. Further, it revealed that the surface (at least the parts that it photographed) was covered in craters, indicating a lack of plate tectonics and weathering of any kind for the last 4 billion years. The probe also found that Mars has no global magnetic field that would protect the planet from potentially life-threatening cosmic rays. The probe was able to calculate the atmospheric pressure on the planet to be about 0.6 kPa (compared to Earth's 101.3 kPa), meaning that liquid water could not exist on the planet's surface. After Mariner 4, the search for life on Mars changed to a search for bacteria-like living organisms rather than for multicellular organisms, as the environment was clearly too harsh for these.

Liquid water is necessary for known life and metabolism, so if water was present on Mars, the chances of it having supported life may have been determinant. The Viking orbiters found evidence of possible river valleys in many areas, erosion and, in the southern hemisphere, branched streams.

The primary mission of the Viking probes of the mid-1970s was to carry out experiments designed to detect microorganisms in Martian soil because the favorable conditions for the evolution of multicellular organisms ceased some four billion years ago on Mars. The tests were formulated to look for microbial life similar to that found on Earth. Of the four experiments, only the Labeled Release (LR) experiment returned a positive result,[dubious ] showing increased ¹⁴CO ₂ production on first exposure of soil to water and nutrients. All scientists agree on two points from the Viking missions: that radiolabeled ¹⁴CO ₂ was evolved in the Labeled Release experiment, and that the GCMS detected no organic molecules. There are vastly different interpretations of what those results imply: A 2011 astrobiology textbook notes that the GCMS was the decisive factor due to which "For most of the Viking scientists, the final conclusion was that the Viking missions failed to detect life in the Martian soil."

Norman Horowitz was the head of the Jet Propulsion Laboratory bioscience section for the Mariner and Viking missions from 1965 to 1976. Horowitz considered that the great versatility of the carbon atom makes it the element most likely to provide solutions, even exotic solutions, to the problems of survival of life on other planets. However, he also considered that the conditions found on Mars were incompatible with carbon based life.

One of the designers of the Labeled Release experiment, Gilbert Levin, believes his results are a definitive diagnostic for life on Mars. Levin's interpretation is disputed by many scientists. A 2006 astrobiology textbook noted that "With unsterilized Terrestrial samples, though, the addition of more nutrients after the initial incubation would then produce still more radioactive gas as the dormant bacteria sprang into action to consume the new dose of food. This was not true of the Martian soil; on Mars, the second and third nutrient injections did not produce any further release of labeled gas." Other scientists argue that superoxides in the soil could have produced this effect without life being present. An almost general consensus discarded the Labeled Release data as evidence of life, because the gas chromatograph and mass spectrometer, designed to identify natural organic matter, did not detect organic molecules. More recently, high levels of organic chemicals, particularly chlorobenzene, were detected in powder drilled from one of the rocks, named " Cumberland", analyzed by the Curiosity rover. The results of the Viking mission concerning life are considered by the general expert community as inconclusive.

In 2007, during a Seminar of the Geophysical Laboratory of the Carnegie Institution (Washington, D.C., US), Gilbert Levin's investigation was assessed once more. Levin still maintains that his original data were correct, as the positive and negative control experiments were in order. Moreover, Levin's team, on April 12, 2012, reported a statistical speculation, based on old data-reinterpreted mathematically through cluster analysis-of the Labeled Release experiments, that may suggest evidence of "extant microbial life on Mars". Critics counter that the method has not yet been proven effective for differentiating between biological and non-biological processes on Earth so it is premature to draw any conclusions.

A research team from the National Autonomous University of Mexico headed by Rafael Navarro-González concluded that the GCMS equipment (TV-GC-MS) used by the Viking program to search for organic molecules, may not be sensitive enough to detect low levels of organics. Klaus Biemann, the principal investigator of the GCMS experiment on Viking wrote a rebuttal. Because of the simplicity of sample handling, TV-GC-MS is still considered the standard method for organic detection on future Mars missions, so Navarro-González suggests that the design of future organic instruments for Mars should include other methods of detection.

After the discovery of perchlorates on Mars by the Phoenix lander, practically the same team of Navarro-González published a paper arguing that the Viking GCMS results were compromised by the presence of perchlorates. A 2011 astrobiology textbook notes that "while perchlorate is too poor an oxidizer to reproduce the LR results (under the conditions of that experiment perchlorate does not oxidize organics), it does oxidize, and thus destroy, organics at the higher temperatures used in the Viking GCMS experiment." Biemann has written a commentary critical of this Navarro-González paper as well, to which the latter have replied; the exchange was published in December 2011.

An artist's concept of the Phoenix spacecraft

The mission landed a robotic spacecraft in the polar region of Mars on May 25, 2008, and it operated until November 10, 2008. One of the mission's two primary objectives was to search for a "habitable zone" in the Martian regolith where microbial life could exist, the other main goal being to study the geological history of water on Mars. The lander has a 2.5 meter robotic arm that was capable of digging shallow trenches in the regolith. There was an electrochemistry experiment which analysed the ions in the regolith and the amount and type of antioxidants on Mars. The Viking program data indicate that oxidants on Mars may vary with latitude, noting that saw fewer oxidants than in its more northerly position. Phoenix landed further north still. Phoenix's preliminary data revealed that Mars soil contains perchlorate, and thus may not be as life-friendly as thought earlier. The pH and salinity level were viewed as benign from the standpoint of biology. The analysers also indicated the presence of bound water and CO ₂. A recent analysis of Martian meteorite EETA79001 found 0.6 ppm ClO ₄−, 1.4 ppm ClO ₃−, and 16 ppm NO ₃−, most likely of Martian origin. The ClO ₃− suggests presence of other highly oxidizing oxychlorines such as ClO ₂− or ClO, produced both by UV oxidation of Cl and X-ray radiolysis of ClO ₄−. Thus only highly refractory and/or well-protected (sub-surface) organics are likely to survive. In addition, recent analysis of the Phoenix WCL showed that the Ca(ClO ₄) ₂ in the Phoenix soil has not interacted with liquid water of any form, perhaps for as long as 600 Myr. If it had, the highly soluble Ca(ClO ₄) ₂ in contact with liquid water would have formed only CaSO ₄. This suggests a severely arid environment, with minimal or no liquid water interaction.

Curiosity rover self-portrait

The Mars Science Laboratory mission is a NASA project that launched on November 26, 2011, the Curiosity rover, a nuclear-powered robotic vehicle, bearing instruments designed to assess past and present habitability conditions on Mars. The Curiosity rover landed on Mars on Aeolis Palus in Gale Crater, near Aeolis Mons (a.k.a. Mount Sharp), on August 6, 2012.

On December 16, 2014, NASA reported the Curiosity rover detected a "tenfold spike", likely localized, in the amount of methane in the Martian atmosphere. Sample measurements taken "a dozen times over 20 months" showed increases in late 2013 and early 2014, averaging "7 parts of methane per billion in the atmosphere". Before and after that, readings averaged around one-tenth that level. In addition, low levels of chlorobenzene (), were detected in powder drilled from one of the rocks, named " Cumberland", analyzed by the Curiosity rover.

The Mars 2020 rover is a Mars planetary rover mission by NASA, launched on July 30, 2020. It is intended to investigate an astrobiologically relevant ancient environment on Mars, investigate its surface geological processes and history, including the assessment of its past habitability and potential for preservation of biosignatures within accessible geological materials.

ExoMars is a European-led multi-spacecraft programme currently under development by the European Space Agency (ESA) and the Russian Federal Space Agency for launch in 2016 and 2020. Its primary scientific mission will be to search for possible biosignatures on Mars, past or present. A rover with a 2 m (6.6 ft) core drill will be used to sample various depths beneath the surface where liquid water may be found and where microorganisms or organic biosignatures might survive cosmic radiation.

Mars sample-return mission - The best life detection experiment proposed is the examination on Earth of a soil sample from Mars. However, the difficulty of providing and maintaining life support over the months of transit from Mars to Earth remains to be solved. Providing for still unknown environmental and nutritional requirements is daunting, so it was concluded that "investigating carbon-based organic compounds would be one of the more fruitful approaches for seeking potential signs of life in returned samples as opposed to culture-based approaches."

Some of the main reasons for colonizing Mars include economic interests, long-term scientific research best carried out by humans as opposed to robotic probes, and sheer curiosity. Surface conditions and the presence of water on Mars make it arguably the most hospitable of the planets in the Solar System, other than Earth. Human colonization of Mars would require in situ resource utilization ( ISRU); A NASA report states that "applicable frontier technologies include robotics, machine intelligence, nanotechnology, synthetic biology, 3-D printing/additive manufacturing, and autonomy. These technologies combined with the vast natural resources should enable, pre- and post-human arrival ISRU to greatly increase reliability and safety and reduce cost for human colonization of Mars."

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The possibility of life on Mars is a subject of interest in astrobiology due to the planet's proximity and similarities to Earth. To date, no proof of past or present life has been found on Mars.

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Rosalind Franklin, previously known as the ExoMars rover, is a planned robotic Mars rover, part of the international ExoMars programme led by the European Space Agency and the Russian Roscosmos State Corporation. The mission was scheduled to launch in July 2020, then postponed to 2022.

The plan calls for a Russian launch vehicle, an ESA carrier module, and a Russian lander named , that will deploy the rover to Mars' surface. Once safely landed, the solar powered rover will begin a seven-month (218- sol) mission to search for the existence of past life on Mars. The Trace Gas Orbiter (TGO), launched in 2016, will operate as Rosalind Franklin's and lander's data-relay satellite.

The rover is named after English chemist and DNA pioneer, Rosalind Franklin.

The Rosalind Franklin rover is an autonomous six-wheeled terrain vehicle with mass approximately 300 kg (660 lb), about 60% more than NASA's 2004 Mars Exploration Rovers Spirit and Opportunity, but about one third that of NASA's Curiosity rover launched in 2011. ESA returned to this original Rover design after NASA descoped its involvement in a joint Rover mission, studied 2009-2012.

The Rover will carry a 2-metre (6 ft 7 in) sub-surface sampling drill and Analytical Laboratory Drawer (ALD), supporting the nine 'Pasteur payload' science instruments. The Rover will search for biomolecules or biosignatures from past life.

The lead builder of the rover, the British division of Airbus Defence and Space, began procuring critical components in March 2014. In December 2014, ESA member states approved the funding for the rover, to be sent on the second launch in 2018, but insufficient funds had already started to threaten a launch delay until 2020. The wheels and suspension system were paid for by the Canadian Space Agency and were manufactured by MDA Corporation in Canada. Each wheel is 25 cm (9.8 in) in diameter. Roscosmos will provide radioisotope heater units (RHU) for the rover to keep its electronic components warm at night. The rover was assembled by Airbus DS in the UK during 2018 and 2019.

By March 2013, the spacecraft was scheduled to launch in 2018 with a Mars landing in early 2019. Delays in European and Russian industrial activities and deliveries of scientific payloads forced the launch to be pushed back. In May 2016, ESA announced that the mission had been moved to the next available launch window of July 2020. ESA ministerial meetings in December 2016 reviewed mission issues including €300 million ExoMars funding and lessons learned from the ExoMars 2016 Schiaparelli mission, which had crashed after its atmospheric entry and parachute descent (the 2020 mission drawing on Schiaparelli heritage for elements of its entry, descent and landing systems). In March 2020, ESA delayed the launch to August-October 2022 due to parachute testing issues.

In July 2018, the European Space Agency launched a public outreach campaign to choose a name for the rover. On 7 February 2019, the ExoMars rover was named Rosalind Franklin in honour of scientist Rosalind Franklin (1920-1958), who made key contributions to the understanding of the molecular structures of DNA (deoxyribonucleic acid), RNA (ribonucleic acid), viruses, coal, and graphite.

The ExoMars mission requires the rover to be capable of driving across the Martian terrain at 70 m (230 ft) per sol (Martian day) to enable it to meet its science objectives. The rover is designed to operate for at least seven months and drive 4 km (2.5 mi), after landing.

Since the rover communicates with the ground controllers via the ExoMars Trace Gas Orbiter (TGO), and the orbiter only passes over the rover approximately twice per sol, the ground controllers will not be able to actively guide the rover across the surface. The Rosalind Franklin rover is therefore designed to navigate autonomously across the Martian surface. Two stereo camera pairs (NavCam and LocCam) allow the rover to build up a 3D map of the terrain, which the navigation software then uses to assess the terrain around the rover so that it avoids obstacles and finds an efficient route to the ground controller specified destination.

On 27 March 2014, a "Mars Yard" was opened at Airbus Defence and Space in Stevenage, UK, to facilitate the development and testing of the rover's autonomous navigation system. The yard is 30 by 13 m (98 by 43 ft) and contains 300 tonnes (330 short tons; 300 long tons) of sand and rocks designed to mimic the terrain of the Martian environment.

The rover will search for two types of subsurface life signatures, morphological and chemical. It will not analyse atmospheric samples, and it has no dedicated meteorological station, but the Kazachok lander that will deploy the rover is equipped with a meteorological station. The 26 kg (57 lb) scientific payload comprises the following survey and analytical instruments:

PanCam has been designed to perform digital terrain mapping for the rover and to search for morphological signatures of past biological activity preserved on the texture of surface rocks. The PanCam Optical Bench (OB) mounted on the Rover mast includes two wide angle cameras (WACs) for multi-spectral stereoscopic panoramic imaging, and a high resolution camera (HRC) for high-resolution colour imaging. PanCam will also support the scientific measurements of other instruments by taking high-resolution images of locations that are difficult to access, such as craters or rock walls, and by supporting the selection of the best sites to carry out exobiology studies. In addition to the OB, PanCam includes a calibration target (PCT), Fiducial Markers (FidMs) and Rover Inspection Mirror (RIM). The PCT's stained glass calibration targets will provide a UV-stable reflectance and colour reference for PanCam and ISEM, allowing for the generation of calibrated data products.

The ISEM optical box will be installed on the rover's mast, below PanCam's HRC, with an electronics box inside the Rover. It will be used to assess bulk mineralogy characterization and remote identification of water-related minerals. Working with PanCam, ISEM will contribute to the selection of suitable samples for further analysis by the other instruments.

WISDOM is a ground-penetrating radar that will explore the subsurface of Mars to identify layering and help select interesting buried formations from which to collect samples for analysis. It can transmit and receive signals using two Vivaldi-antennas mounted on the aft section of the rover, with electronics inside the Rover. Electromagnetic waves penetrating into the ground are reflected at places where there is a sudden transition in the electrical parameters of the soil. By studying these reflections it is possible to construct a stratigraphic map of the subsurface and identify underground targets down to 2 to 3 m (7 to 10 ft) in depth, comparable to the 2 m reach of the rover's drill. These data, combined with those produced by the other survey instruments and by the analyses carried out on previously collected samples, will be used to support drilling activities.

Adron-RM is a neutron spectrometer to search for subsurface water ice and hydrated minerals. It is housed inside the Rover and will be used in combination with the WISDOM ground-penetrating radar to study the subsurface beneath the rover and to search for optimal sites for drilling and sample collection.

CLUPI, mounted on the drill box, will visually study rock targets at close range (50 cm/20 in) with sub-millimetre resolution. This instrument will also investigate the fines produced during drilling operations, and image samples collected by the drill. CLUPI has variable focusing and can obtain high-resolution images at longer distances. The CLUPI imaging unit is complemented by two mirrors and a calibration target.

Ma_MISS is an infrared spectrometer located inside the core drill. Ma_MISS will observe the lateral wall of the borehole created by the drill to study the subsurface stratigraphy, to understand the distribution and state of water-related minerals, and to characterise the geophysical environment. The analyses of unexposed material by Ma_MISS, together with data obtained with the spectrometers located inside the rover, will be crucial for the unambiguous interpretation of the original conditions of Martian rock formation. The composition of the regolith and crustal rocks provides important information about the geologic evolution of the near-surface crust, the evolution of the atmosphere and climate, and the existence of past life.

MicrOmega is an infrared hyperspectral microscope housed within the Rover's ALD that can analyse the powder material derived from crushing samples collected by the core drill. Its objective is to study mineral grain assemblages in detail to try to unravel their geological origin, structure, and composition. These data will be vital for interpreting past and present geological processes and environments on Mars. Because MicrOmega is an imaging instrument, it can also be used to identify grains that are particularly interesting, and assign them as targets for Raman and MOMA-LDMS observations.

RLS is a Raman spectrometer housed within the ALD that will provide geological and mineralogical context information complementary to that obtained by MicrOmega. It is a very fast and useful technique employed to identify mineral phases produced by water-related processes. It will help to identify organic compounds and search for life by identifying the mineral products and indicators of biologic activities ( biosignatures).

MOMA is the rover's largest instrument, housed within the ALD. It will conduct a broad-range, very-high sensitivity search for organic molecules in the collected sample. It includes two different ways for extracting organics: laser desorption and thermal volatilisation, followed by separation using four GC-MS columns. The identification of the evolved organic molecules is performed with an ion trap mass spectrometer. The Max Planck Institute for Solar System Research is leading the development. International partners include NASA. The mass spectrometer is provided from the Goddard Space Flight Center, while the GC is provided by the two French institutes LISA and LATMOS. The UV-Laser is being developed by the Laser Zentrum Hannover.

Sampling from beneath the martian surface with the intent to reach and analyze material unaltered or minimally affected by cosmic radiation is the strongest advantage of Rosalind Franklin. The ExoMars core drill was fabricated in Italy with heritage from the earlier DeeDri development, and incorporates the Ma_MISS instrument (see above). It is designed to acquire soil samples down to a maximum depth of 2 metres (6 ft 7 in) in a variety of soil types. The drill will acquire a core sample 1 cm (0.4 in) in diameter by 3 cm (1.2 in) in length, extract it and deliver it to the Sample Container of the ALD's Core Sample Transport Mechanism (CSTM). The CSTM drawer is then closed and the sample dropped into a Crushing Station. The resulting powder is fed by a dosing station into receptacles on the ALD's sample carousel: either the Refillable Container - for examination by MicrOmega, RLS and MOMA-LDMS - or a MOMA-GC oven. The system will complete experiment cycles and at least two vertical surveys down to 2 m (with four sample acquisitions each). This means that a minimum number of 17 samples shall be acquired and delivered by the drill for subsequent analysis.

The proposed payload has changed several times. The last major change was after the program switched from the larger rover concept back to the previous 300 kg (660 lb) rover design in 2012.

Mars X-Ray Diffractometer (Mars-XRD) - Powder diffraction of X-rays would have determined the composition of crystalline minerals. This instrument includes also an X-ray fluorescence capability that can provide useful atomic composition information. The identification of concentrations of carbonates, sulphides or other aqueous minerals may be indicative of a Martian [hydrothermal] system capable of preserving traces of life. In other words, it would have examined the past Martian environmental conditions, and more specifically the identification of conditions related to life.

The Urey instrument was planned to search for organic compounds in Martian rocks and soils as evidence for past life and/or prebiotic chemistry. Starting with a hot water extraction, only soluble compounds are left for further analysis. Sublimation, and capillary electrophoresis makes it possible to identify amino acids. The detection would have been done by laser-induced fluorescence, a highly sensitive technique, capable of parts-per-trillion sensitivity. These measurements were to be made at a thousand times greater sensitivity than the Viking GCMS experiment.

Miniaturised Mössbauer Spectrometer (MIMOS-II) provides the mineralogical composition of iron-bearing surface rocks, sediments and soils. Their identification was to aid in understanding water and climate evolution and search for biomediated iron-sulfides and magnetites, which could provide evidence for former life on Mars.

The Life Marker Chip (LMC) was for some time part of the planned payload. This instrument was intended to use a surfactant solution to extract organic matter from samples of martian rock and soil, then detect the presence of specific organic compounds using an antibody-based assay.

Mars Infrared Mapper (MIMA), a Fourier IR spectrometer operating in the 2-25 µm range that was to be mounted on the rover's mast to investigate the martian surface and atmosphere.

After a review by an ESA-appointed panel, a short list of four sites was formally recommended in October 2014 for further detailed analysis. These landing sites exhibit evidence of a complex aqueous history in the past.

On 21 October 2015, Oxia Planum was chosen as the preferred landing site for the rover, with Aram Dorsum and Mawrth Vallis as backup options. In March 2017 the Landing Site Selection Working Group narrowed the choice to Oxia Planum and Mawrth Vallis, and in November 2018, Oxia Planum was once again chosen, pending sign-off by the heads of the European and Russian space agencies.

After lands, it will extend a ramp to deploy the Rosalind Franklin rover to the surface. The lander will remain stationary and will start a two-year mission to investigate the surface environment at the landing site.

1. ^ @ESA_ExoMars (12 March 2020). "#ExoMars to take off for the Red Planet in 2022. Check out the new timeline for mission success on the Red Planet! pbs.twimg.com/media/ES52icEX0AELyns?format=jpg" (Tweet) - via Twitter.

2. ^ Vago, Jorge; Witasse, Olivier; Baglioni, Pietro; Haldemann, Albert; Gianfiglio, Giacinto; et al. (August 2013). "ExoMars: ESA's Next Step in Mars Exploration" (PDF). Bulletin. European Space Agency (155): 12-23.

3. ^ Vego, J. L.; et al. (2009). ExoMars Status (PDF). 20th Mars Exploration Program Analysis Group Meeting. 3-4 March 2009. Arlington, Virginia. European Space Agency. Archived from the original (PDF) on 9 April 2009.

4. ^ "Press Info: ExoMars Status" (Press release). Thales Group. 8 May 2012. Archived from the original on 3 December 2013.

5. ^ "The ExoMars Instruments". European Space Agency. 1 February 2008. Archived from the original on 26 October 2012.

6. ^ "Europe Agrees to Fund Ariane 6 Orbital Launcher". ABC News. Berlin, Germany. Associated Press. 2 December 2014. ESA's member states also approved funding to upgrade the smaller Vega launch vehicle, continue participating in the International Space Station, and proceed with the second part of its ExoMars mission.

7. ^ ESA Prepares for ExoMars Rover 2020 Launch at Mars and on Earth. Emily Lakdawalla, The Planetary Society. 30 May 2019.

8. ^ Zak, Anatoly (28 July 2016). "ExoMars-2016 mission". Russianspaceweb.com. In 2018, a Russian-built radioactive heat generator would be installed on the ExoMars rover, along with possible suit of Russian instruments.

9. ^ Lancaster, R.; Silva, N.; Davies, A.; Clemmet, J. (2011). ExoMars Rover GNC Design and Development. 8th Int'l ESA Conference on Guidance & Navigation Control Systems. 5-10 June 2011. Carlsbad, Czech Republic.

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Rosalind Franklin , previously known as the ExoMars rover, is a planned robotic Mars rover, part of the international ExoMars programme led by the European Space Agency and the Russian Roscosmos State Corporation. The mission was scheduled to launch in July 2020, then postponed to 2022.

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NASA

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NASA's real-time portal for Mars exploration, featuring the latest news, images, and discoveries from the Red Planet.

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Wikipedia

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The planet Mars has been explored remotely by spacecraft. Probes sent from Earth, beginning in the late 20th century, have yielded a large increase in knowledge about the Martian system, focused primarily on understanding its geology and habitability potential. Engineering interplanetary journeys is complicated and the exploration of Mars has experienced a high failure rate, especially the early attempts. Roughly sixty percent of all spacecraft destined for Mars failed before completing their missions and some failed before their observations could begin. Some missions have met with unexpected success, such as the twin Mars Exploration Rovers, which operated for years beyond their specification.

On June 10, 2018, Opportunity rover fell silent, leaving of the Mars Science Laboratory mission with six orbiters surveying the planet: Mars Odyssey, Mars Express, Mars Reconnaissance Orbiter, Mars Orbiter Mission, MAVEN, and the Trace Gas Orbiter, which have contributed massive amounts of information about Mars. The stationary lander is investigating the deep interior of Mars. No sample return missions have been attempted for Mars and an attempted return mission for Mars' moon Phobos (Fobos-Grunt) failed at launch in 2011.

Five more missions are in the late stages of development and fabrication, and will be launched between 2020 and 2021. These include the ExoMars Rosalind Franklin rover and landing platform Kazachok by Roscosmos and ESA, NASA's Mars 2020, the 2020 Chinese Mars Mission, the Hope Mars Mission by the United Arab Emirates, and India's Mars Orbiter Mission 2.

Mars has long been the subject of human interest. Early telescopic observations revealed color changes on the surface that were attributed to seasonal vegetation and apparent linear features were ascribed to intelligent design. Further telescopic observations found two moons, Phobos and Deimos, polar ice caps and the feature now known as Olympus Mons, the Solar System's second tallest mountain. The discoveries piqued further interest in the study and exploration of the red planet. Mars is a rocky planet, like Earth, that formed around the same time, yet with only half the diameter of Earth, and a far thinner atmosphere; it has a cold and desert-like surface.

One way the surface of Mars has been categorized, is by thirty " quadrangles", with each quadrangle named for a prominent physiographic feature within that quadrangle.

The minimum-energy launch windows for a Martian expedition occur at intervals of approximately two years and two months (specifically 780 days, the planet's synodic period with respect to Earth). In addition, the lowest available transfer energy varies on a roughly 16-year cycle. For example, a minimum occurred in the 1969 and 1971 launch windows, rising to a peak in the late 1970s, and hitting another low in 1986 and 1988.

Starting in 1960, the Soviets launched a series of probes to Mars including the first intended flybys and hard ( impact) landing ( Mars 1962B). The first successful flyby of Mars was on 14-15 July 1965, by NASA's Mariner 4. On November 14, 1971, Mariner 9 became the first space probe to orbit another planet when it entered into orbit around Mars. The amount of data returned by probes increased dramatically as technology improved.

The first to contact the surface were two Soviet probes: Mars 2 lander on November 27 and Mars 3 lander on December 2, 1971-Mars 2 failed during descent and Mars 3 about twenty seconds after the first Martian soft landing. Mars 6 failed during descent but did return some corrupted atmospheric data in 1974. The 1975 NASA launches of the Viking program consisted of two orbiters, each with a lander that successfully soft landed in 1976. remained operational for six years, for three. The Viking landers relayed the first color panoramas of Mars.

The Soviet probes Phobos 1 and 2 were sent to Mars in 1988 to study Mars and its two moons, with a focus on Phobos. Phobos 1 lost contact on the way to Mars. Phobos 2, while successfully photographing Mars and Phobos, failed before it was set to release two landers to the surface of Phobos.

Mars has a reputation as a difficult space exploration target; just 25 of 55 missions through 2019, or 45.5%, have been fully successful, with a further three partially successful and partially failed. However, of the sixteen missions since 2001, twelve of those have been successful and eight of those are still operational.

Missions that ended prematurely after Phobos 1 and 2 (1988) include (see Probing difficulties section for more details):

Following the 1993 failure of the Mars Observer orbiter, the NASA Mars Global Surveyor achieved Mars orbit in 1997. This mission was a complete success, having finished its primary mapping mission in early 2001. Contact was lost with the probe in November 2006 during its third extended program, spending exactly 10 operational years in space. The NASA Mars Pathfinder, carrying a robotic exploration vehicle , landed in the Ares Vallis on Mars in the summer of 1997, returning many images.

landed on the north polar region of Mars on May 25, 2008. Its robotic arm dug into the Martian soil and the presence of water ice was confirmed on June 20, 2008. The mission concluded on November 10, 2008 after contact was lost. In 2008, the price of transporting material from the surface of Earth to the surface of Mars was approximately US$309,000 per kilogram.

came within 250 km of Mars during its 2007 flyby. flew by Mars in February 2009 for a gravity assist on its way to investigate Vesta and Ceres.

NASA's Mars Odyssey orbiter entered Mars orbit in 2001. Odyssey's Gamma Ray Spectrometer detected significant amounts of hydrogen in the upper metre or so of regolith on Mars. This hydrogen is thought to be contained in large deposits of water ice.

The Mars Express mission of the European Space Agency (ESA) reached Mars in 2003. It carried the lander, which was not heard from after being released and was declared lost in February 2004. Beagle 2 was located in January 2015 by HiRise camera on NASA's Mars Reconnaissance Orbiter (MRO) having landed safely but failed to fully deploy its solar panels and antenna. In early 2004, the Mars Express Planetary Fourier Spectrometer team announced the orbiter had detected methane in the Martian atmosphere, a potential biosignature. ESA announced in June 2006 the discovery of aurorae on Mars by the Mars Express.

In January 2004, the NASA twin Mars Exploration Rovers named (MER-A) and Opportunity (MER-B) landed on the surface of Mars. Both have met and exceeded all their science objectives. Among the most significant scientific returns has been conclusive evidence that liquid water existed at some time in the past at both landing sites. Martian dust devils and windstorms have occasionally cleaned both rovers' solar panels, and thus increased their lifespan. Spirit rover (MER-A) was active until 2010, when it stopped sending data because it got stuck in a sand dune and was unable to reorient itself to recharge its batteries.

On 10 March 2006, NASA's Mars Reconnaissance Orbiter (MRO) probe arrived in orbit to conduct a two-year science survey. The orbiter began mapping the Martian terrain and weather to find suitable landing sites for upcoming lander missions. The MRO captured the first image of a series of active avalanches near the planet's north pole in 2008.

The Mars Science Laboratory mission was launched on November 26, 2011 and it delivered the Curiosity rover on the surface of Mars on August 6, 2012 UTC. It is larger and more advanced than the Mars Exploration Rovers, with a velocity of up to 90 meters per hour (295 feet per hour). Experiments include a laser chemical sampler that can deduce the composition of rocks at a distance of 7 meters.

The Indian Space Research Organisation (ISRO) launched their Mars Orbiter Mission (MOM) on November 5, 2013 and it was inserted into Mars orbit on 24 September 2014. India's ISRO is the fourth space agency to reach Mars, after the Soviet space program, NASA and ESA. India successfully placed a spacecraft into Mars orbit on its maiden attempt.

The ExoMars Trace Gas Orbiter arrived at Mars in 2016 and deployed the Schiaparelli EDM lander, a test lander. Schiaparelli crashed on surface, but it transmitted key data during its parachute descent, so the test was declared a partial success.

The following entails a brief overview of Mars exploration, oriented towards orbiters and flybys; see also Mars landing and Mars rover.

Between 1960 and 1969, the Soviet Union launched nine probes intended to reach Mars. They all failed: three at launch; three failed to reach near-Earth orbit; one during the burn to put the spacecraft into trans-Mars trajectory; and two during the interplanetary orbit.

The Mars 1M programs (sometimes dubbed Marsnik in Western media) was the first Soviet unmanned spacecraft interplanetary exploration program, which consisted of two flyby probes launched towards Mars in October 1960, Mars 1960A and Mars 1960B (also known as Korabl 4 and Korabl 5 respectively). After launch, the third stage pumps on both launchers were unable to develop enough pressure to commence ignition, so Earth parking orbit was not achieved. The spacecraft reached an altitude of 120 km before reentry.

The first success

Mars 1 (1962 Beta Nu 1), an automatic interplanetary spacecraft launched to Mars on November 1, 1962, was the first probe of the Soviet Mars probe program to achieve interplanetary orbit. Mars 1 was intended to fly by the planet at a distance of about 11,000 km and take images of the surface as well as send back data on cosmic radiation, micrometeoroid impacts and Mars' magnetic field, radiation environment, atmospheric structure, and possible organic compounds. Sixty-one radio transmissions were held, initially at 2-day intervals and later at 5-day intervals, from which a large amount of interplanetary data was collected. On 21 March 1963, when the spacecraft was at a distance of 106,760,000 km from Earth, on its way to Mars, communications ceased due to failure of its antenna orientation system.

The USSR intended to have the first artificial satellite of Mars beating the planned American Mariner 8 and Mariner 9 Mars orbiters. In May 1971, one day after Mariner 8 malfunctioned at launch and failed to reach orbit, Cosmos 419 (Mars 1971C), a heavy probe of the Soviet Mars program M-71, also failed to launch. This spacecraft was designed as an orbiter only, while the next two probes of project M-71, Mars 2 and Mars 3, were multipurpose combinations of an orbiter and a lander with small skis-walking rovers that would be the first planet rovers outside the Moon. They were successfully launched in mid-May 1971 and reached Mars about seven months later. On November 27, 1971 the lander of Mars 2 crash-landed due to an on-board computer malfunction and became the first man-made object to reach the surface of Mars. On 2 December 1971, the Mars 3 lander became the first spacecraft to achieve a soft landing, but its transmission was interrupted after 14.5 seconds.

The Mars 2 and 3 orbiters sent back a relatively large volume of data covering the period from December 1971 to March 1972, although transmissions continued through to August. By 22 August 1972, after sending back data and a total of 60 pictures, Mars 2 and 3 concluded their missions. The images and data enabled creation of surface relief maps, and gave information on the Martian gravity and magnetic fields.

In 1973, the Soviet Union sent four more probes to Mars: the Mars 4 and Mars 5 orbiters and the Mars 6 and Mars 7 flyby/lander combinations. All missions except Mars 7 sent back data, with Mars 5 being most successful. Mars 5 transmitted just 60 images before a loss of pressurization in the transmitter housing ended the mission. Mars 6 lander transmitted data during descent, but failed upon impact. Mars 4 flew by the planet at a range of 2200 km returning one swath of pictures and radio occultation data, which constituted the first detection of the nightside ionosphere on Mars. Mars 7 probe separated prematurely from the carrying vehicle due to a problem in the operation of one of the onboard systems ( attitude control or retro-rockets) and missed the planet by 1,300 kilometres (8.7×10 −6 au).

In 1964, NASA's Jet Propulsion Laboratory made two attempts at reaching Mars. Mariner 3 and Mariner 4 were identical spacecraft designed to carry out the first flybys of Mars. Mariner 3 was launched on November 5, 1964, but the shroud encasing the spacecraft atop its rocket failed to open properly, dooming the mission. Three weeks later, on November 28, 1964, Mariner 4 was launched successfully on a 7½-month voyage to Mars..

Mariner 4 flew past Mars on July 14, 1965, providing the first close-up photographs of another planet. The pictures, gradually played back to Earth from a small tape recorder on the probe, showed impact craters. It provided radically more accurate data about the planet; a surface atmospheric pressure of about 1% of Earth's and daytime temperatures of −100 °C (−148 °F) were estimated. No magnetic field or Martian radiation belts were detected. The new data meant redesigns for then planned Martian landers, and showed life would have a more difficult time surviving there than previously anticipated.

NASA continued the Mariner program with another pair of Mars flyby probes, Mariner 6 and 7. They were sent at the next launch window, and reached the planet in 1969. During the following launch window the Mariner program again suffered the loss of one of a pair of probes. Mariner 9 successfully entered orbit about Mars, the first spacecraft ever to do so, after the launch time failure of its sister ship, Mariner 8. When Mariner 9 reached Mars in 1971, it and two Soviet orbiters ( Mars 2 and Mars 3, see Mars probe program above) found that a planet-wide dust storm was in progress. The mission controllers used the time spent waiting for the storm to clear to have the probe rendezvous with, and photograph, Phobos. When the storm cleared sufficiently for Mars' surface to be photographed by Mariner 9, the pictures returned represented a substantial advance over previous missions. These pictures were the first to offer more detailed evidence that liquid water might at one time have flowed on the planetary surface. They also finally discerned the true nature of many Martian albedo features. For example, Nix Olympica was one of only a few features that could be seen during the planetary duststorm, revealing it to be the highest mountain ( volcano, to be exact) on any planet in the entire Solar System, and leading to its reclassification as Olympus Mons.

The Viking program launched Viking 1 and Viking 2 spacecraft to Mars in 1975; The program consisted of two orbiters and two landers - these were the second and third spacecraft to successfully land on Mars.

The primary scientific objectives of the lander mission were to search for biosignatures and observe meteorologic, seismic and magnetic properties of Mars. The results of the biological experiments on board the Viking landers remain inconclusive, with a reanalysis of the Viking data published in 2012 suggesting signs of microbial life on Mars.

The Viking orbiters revealed that large floods of water carved deep valleys, eroded grooves into bedrock, and traveled thousands of kilometers. Areas of branched streams, in the southern hemisphere, suggest that rain once fell.

Mars Pathfinder was a U.S. spacecraft that landed a base station with a roving probe on Mars on July 4, 1997. It consisted of a lander and a small 10.6 kilograms (23 lb) wheeled robotic rover named Sojourner, which was the first rover to operate on the surface of Mars. In addition to scientific objectives, the Mars Pathfinder mission was also a "proof-of-concept" for various technologies, such as an airbag landing system and automated obstacle avoidance, both later exploited by the Mars Exploration Rovers.

After the 1992 failure of NASA's Mars Observer orbiter, NASA retooled and launched Mars Global Surveyor (MGS). Mars Global Surveyor launched on November 7, 1996, and entered orbit on September 12, 1997. After a year and a half trimming its orbit from a looping ellipse to a circular track around the planet, the spacecraft began its primary mapping mission in March 1999. It observed the planet from a low-altitude, nearly polar orbit over the course of one complete Martian year, the equivalent of nearly two Earth years. Mars Global Surveyor completed its primary mission on January 31, 2001, and completed several extended mission phases.

The mission studied the entire Martian surface, atmosphere, and interior, and returned more data about the red planet than all previous Mars missions combined. The data has been archived and remains available publicly.

Among key scientific findings, Global Surveyor took pictures of gullies and debris flow features that suggest there may be current sources of liquid water, similar to an aquifer, at or near the surface of the planet. Similar channels on Earth are formed by flowing water, but on Mars the temperature is normally too cold and the atmosphere too thin to sustain liquid water. Nevertheless, many scientists hypothesize that liquid groundwater can sometimes surface on Mars, erode gullies and channels, and pool at the bottom before freezing and evaporating.

Magnetometer readings showed that the planet's magnetic field is not globally generated in the planet's core, but is localized in particular areas of the crust. New temperature data and closeup images of the Martian moon Phobos showed that its surface is composed of powdery material at least 1 metre (3 feet) thick, caused by millions of years of meteoroid impacts. Data from the spacecraft's laser altimeter gave scientists their first 3-D views of Mars' north polar ice cap.

Faulty software uploaded to the vehicle in June 2006 caused the spacecraft to orient its solar panels incorrectly several months later, resulting in battery overheating and subsequent failure. On November 5, 2006 MGS lost contact with Earth. NASA ended efforts to restore communication on January 28, 2007.

In 2001, NASA's Mars Odyssey orbiter arrived at Mars. Its mission is to use spectrometers and imagers to hunt for evidence of past or present water and volcanic activity on Mars. In 2002, it was announced that the probe's gamma-ray spectrometer and neutron spectrometer had detected large amounts of hydrogen, indicating that there are vast deposits of water ice in the upper three meters of Mars' soil within 60° latitude of the south pole.

On June 2, 2003, the European Space Agency's Mars Express set off from Baikonur Cosmodrome to Mars. The Mars Express craft consists of the Mars Express Orbiter and the stationary lander Beagle 2. The lander carried a digging device and the smallest mass spectrometer created to date, as well as a range of other devices, on a robotic arm in order to accurately analyze soil beneath the dusty surface to look for biosignatures and biomolecules.

The orbiter entered Mars orbit on December 25, 2003, and Beagle 2 entered Mars' atmosphere the same day. However, attempts to contact the lander failed. Communications attempts continued throughout January, but Beagle 2 was declared lost in mid-February, and a joint inquiry was launched by the UK and ESA. The Mars Express Orbiter confirmed the presence of water ice and carbon dioxide ice at the planet's south pole, while NASA had previously confirmed their presence at the north pole of Mars.

The lander's fate remained a mystery until it was located intact on the surface of Mars in a series of images from the Mars Reconnaissance Orbiter. The images suggest that two of the spacecraft's four solar panels failed to deploy, blocking the spacecraft's communications antenna. Beagle 2 is the first British and first European probe to achieve a soft landing on Mars.

NASA's Mars Exploration Rover Mission (MER), started in 2003, was a robotic space mission involving two rovers, Spirit (MER-A) and Opportunity, (MER-B) that explored the Martian surface geology. The mission's scientific objective was to search for and characterize a wide range of rocks and soils that hold clues to past water activity on Mars. The mission was part of NASA's Mars Exploration Program, which includes three previous successful landers: the two Viking program landers in 1976; and Mars Pathfinder probe in 1997.

The Mars Reconnaissance Orbiter (MRO) is a multipurpose spacecraft designed to conduct reconnaissance and exploration of Mars from orbit. The US$720 million spacecraft was built by Lockheed Martin under the supervision of the Jet Propulsion Laboratory, launched August 12, 2005, and entered Mars orbit on March 10, 2006.

The MRO contains a host of scientific instruments such as the HiRISE camera, CTX camera, CRISM, and SHARAD. The HiRISE camera is used to analyze Martian landforms, whereas CRISM and SHARAD can detect water, ice, and minerals on and below the surface. Additionally, MRO is paving the way for upcoming generations of spacecraft through daily monitoring of Martian weather and surface conditions, searching for future landing sites, and testing a new telecommunications system that enable it to send and receive information at an unprecedented bitrate, compared to previous Mars spacecraft. Data transfer to and from the spacecraft occurs faster than all previous interplanetary missions combined and allows it to serve as an important relay satellite for other missions.

The ESA Rosetta space probe mission to the comet 67P/Churyumov-Gerasimenko flew within 250 km of Mars on February 25, 2007, in a gravitational slingshot designed to slow and redirect the spacecraft.

The NASA Dawn spacecraft used the gravity of Mars in 2009 to change direction and velocity on its way to Vesta, and tested out Dawn's cameras and other instruments on Mars.

On November 8, 2011, Russia's Roscosmos launched an ambitious mission called Fobos-Grunt. It consisted of a lander aimed to retrieve a sample back to Earth from Mars' moon Phobos, and place the Chinese Yinghuo-1 probe in Mars' orbit. The Fobos-Grunt mission suffered a complete control and communications failure shortly after launch and was left stranded in low Earth orbit, later falling back to Earth. The Yinghuo-1 satellite and Fobos-Grunt underwent destructive re-entry on January 15, 2012, finally disintegrating over the Pacific Ocean.

The NASA Mars Science Laboratory mission with its rover named , was launched on November 26, 2011, and landed on Mars on August 6, 2012 on Aeolis Palus in Gale Crater. The rover carries instruments designed to look for past or present conditions relevant to the past or present habitability of Mars.

NASA's MAVEN is an orbiter mission to study the upper atmosphere of Mars. It will also serve as a communications relay satellite for robotic landers and rovers on the surface of Mars. MAVEN was launched 18 November 2013 and reached Mars on 22 September 2014.

The Mars Orbiter Mission, also called Mangalyaan, was launched on 5 November 2013 by the Indian Space Research Organisation (ISRO). It was successfully inserted into Martian orbit on 24 September 2014. The mission is a technology demonstrator, and as secondary objective, it will also study the Martian atmosphere. This is India's first mission to Mars, and with it, ISRO became the fourth space agency to successfully reach Mars after the Soviet Union, NASA (USA) and ESA (Europe). It also made ISRO the second space agency to reach Mars orbit on its first attempt (the first national one, after the international ESA), and also the first Asian country to successfully send an orbiter to Mars. It was completed in a record low budget of $71 million, making it the least-expensive Mars mission to date.

The ExoMars Trace Gas Orbiter is an atmospheric research orbiter built in collaboration between ESA and Roscosmos. It was injected into Mars orbit on 19 October 2016 to gain a better understanding of methane () and other trace gases present in the Martian atmosphere that could be evidence for possible biological or geological activity. The Schiaparelli EDM lander was destroyed when trying to land on the surface of Mars.

In August 2012, NASA selected , a $425 million lander mission with a heat flow probe and seismometer, to determine the deep interior structure of Mars. Two flyby CubeSats called MarCO were launched with InSight on 5 May 2018 to provide real-time telemetry during the entry and landing of InSight. The CubeSats separated from the Atlas V booster 1.5 hours after launch and traveled their own trajectories to Mars. InSight landed successfully on Mars on 26 November 2018.

The Finnish-Russian Mars MetNet concept would use multiple small meteorological stations on Mars to establish a widespread observation network to investigate the planet's atmospheric structure, physics and meteorology. The MetNet precursor or demonstrator was considered for a piggyback launch on Fobos-Grunt, and on the two proposed to fly on the 2016 and 2020 ExoMars spacecraft.

The Mars-Grunt is a Russian mission concept to bring a sample of Martian soil to Earth.

A ESA-NASA team produced a three-launch architecture concept for a Mars sample return, which uses a rover to cache small samples, a Mars ascent stage to send it into orbit, and an orbiter to rendezvous with it above Mars and take it to Earth. Solar-electric propulsion could allow a one launch sample return instead of three.

The Mars Scout Program's SCIM would involve a probe grazing the upper atmosphere of Mars to collect dust and air for return to Earth.

JAXA is working on a mission concept called MELOS rover that would look for biosignatures of extant life on Mars.

Other future mission concepts include polar probes, Martian aircraft and a network of small meteorological stations. Longterm areas of study may include Martian lava tubes, resource utilization, and electronic charge carriers in rocks. Micromissions are another possibility, such as piggybacking a small spacecraft on an Ariane 5 rocket and using a lunar gravity assist to get to Mars.

The human exploration of Mars has been an aspiration since the earliest days of modern rocketry; Robert H. Goddard credits the idea of reaching Mars as his own inspiration to study the physics and engineering of space flight. Proposals for human exploration of Mars have been made throughout the history of space exploration; currently there are multiple active plans and programs to put humans on Mars within the next ten to thirty years, both governmental and private, some of which are listed below.

Human exploration by the United States was identified as a long-term goal in the Vision for Space Exploration announced in 2004 by then US President George W. Bush. The planned spacecraft would be used to send a human expedition to Earth's moon by 2020 as a stepping stone to a Mars expedition. On September 28, 2007, NASA administrator Michael D. Griffin stated that NASA aims to put a person on Mars by 2037.

On December 2, 2014, NASA's Advanced Human Exploration Systems and Operations Mission Director Jason Crusan and Deputy Associate Administrator for Programs James Reuthner announced tentative support for the Boeing "Affordable Mars Mission Design" including radiation shielding, centrifugal artificial gravity, in-transit consumable resupply, and a lander which can return. Reuthner suggested that if adequate funding was forthcoming, the proposed mission would be expected in the early 2030s.

On October 8, 2015, NASA published its official plan for human exploration and colonization of Mars. They called it "Journey to Mars". The plan operates through three distinct phases leading up to fully sustained colonization.

The first stage, already underway, is the "Earth Reliant" phase. This phase continues utilizing the International Space Station until 2024; validating deep space technologies and studying the effects of long duration space missions on the human body.

The second stage, "Proving Ground," moves away from Earth reliance and ventures into cislunar space for most of its tasks. This is when NASA plans to capture an asteroid (planned for 2020), test deep space habitation facilities, and validate capabilities required for human exploration of Mars. Finally, phase three is the transition to independence from Earth resources.

The last stage, the "Earth Independent" phase, includes long term missions on the lunar surface which leverage surface habitats that only require routine maintenance, and the harvesting of Martian resources for fuel, water, and building materials. NASA is still aiming for human missions to Mars in the 2030s, though Earth independence could take decades longer.

On August 28, 2015, NASA funded a year long simulation to study the effects of a year long Mars mission on six scientists. The scientists lived in a bio dome on a Mauna Loa mountain in Hawaii with limited connection to the outside world and were only allowed outside if they were wearing spacesuits.

NASAs human Mars exploration plans have evolved through the NASA Mars Design Reference Missions, a series of design studies for human exploration of Mars.

In 2017 the focus of NASA shifted to a return to the Moon by 2024 with the Artemis program, a flight to Mars could follow after this project.

The long-term goal of the private corporation SpaceX is the establishment of routine flights to Mars to enable colonization. To this end, the company is developing Starship, a spacecraft capable of crew transportation to Mars and other celestial bodies, along with its booster Super Heavy. In 2017 SpaceX announced plans to send two uncrewed Starships to Mars by 2022, followed by two more uncrewed flights and two crewed flights in 2024. Starship is planned to have a payload of at least 100 tonnes. Starship is designed to use a combination of aerobraking and propulsive descent, utilizing fuel produced from a Mars ( in situ resource utilization) facility. As of mid-September 2019, the Starship development program has seen successful testing of a test bed (Starhopper), with an orbital prototype (Starship Mk3) under construction in Boca Chica, Texas, as of December 2019. Launch Complex 39A at Kennedy Space Center will have a dedicated launch pad, fuelling and supporting facilities added for Starship missions.

Mars Direct, a low-cost human mission proposed by Robert Zubrin, founder of the Mars Society, would use heavy-lift Saturn V class rockets, such as the Ares V, to skip orbital construction, LEO rendezvous, and lunar fuel depots. A modified proposal, called " Mars to Stay", involves not returning the first immigrant explorers immediately, if ever (see Colonization of Mars).

Probing difficulties

The challenge, complexity and length of Mars missions have led to many mission failures. The high failure rate of missions launched from Earth attempting to explore Mars is informally called the "Mars Curse" or "Martian Curse". The phrase "Galactic Ghoul" or "Great Galactic Ghoul", referring to a fictitious space monster that subsists on a diet of Mars probes, was coined in 1997 by Time Magazine journalist Donald Neff, and is sometimes facetiously used to "explain" the recurring difficulties.

Two Soviet probes were sent to Mars in 1988 as part of the Phobos program. Phobos 1 operated normally until an expected communications session on 2 September 1988 failed to occur. The problem was traced to a software error, which deactivated attitude thrusters causing the spacecrafts' solar arrays to no longer point at the Sun, depleting Phobos 1 batteries. Phobos 2 operated normally throughout its cruise and Mars orbital insertion phases on January 29, 1989, gathering data on the Sun, interplanetary medium, Mars, and Phobos. Shortly before the final phase of the mission - during which the spacecraft was to approach within 50 m of Phobos' surface and release two landers, one a mobile 'hopper', the other a stationary platform - contact with Phobos 2 was lost. The mission ended when the spacecraft signal failed to be successfully reacquired on March 27, 1989. The cause of the failure was determined to be a malfunction of the on-board computer.

Just a few years later in 1992 Mars Observer, launched by NASA, failed as it approached Mars. Mars 96, an orbiter launched on November 16, 1996 by Russia failed, when the planned second burn of the Block D-2 fourth stage did not occur.

Following the success of Global Surveyor and Pathfinder, another spate of failures occurred in 1998 and 1999, with the Japanese Nozomi orbiter and NASA's Mars Climate Orbiter, Mars Polar Lander, and Deep Space 2 penetrators all suffering various fatal errors. The Mars Climate Orbiter was noted for mixing up U.S. customary units with metric units, causing the orbiter to burn up while entering Mars' atmosphere.

The European Space Agency has also attempted to land two probes on the Martian surface; Beagle 2, a British-built lander that failed to deploy its solar arrays properly after touchdown in December 2003, and Schiaparelli, which was flown along the ExoMars Trace Gas Orbiter. Contact with the Schiaparelli EDM lander was lost 50 seconds before touchdown. It was later confirmed that the lander struck the surface at a high velocity, possibly exploding.

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Mars - A Warmer, Wetter Planet by Jeffrey S. Kargel (published July 2004; ISBN 978-1-85233-568-7)

The Compact NASA Atlas of the Solar System by Ronald Greeley and Raymond Batson (published January 2002; ISBN 0-521-80633-X)

Mars: The NASA Mission Reports / edited by Robert Godwin (2000) ISBN 1-896522-62-9

^α The diagram includes missions that are active on the surface, such as operational rovers and landers, as well as probes in Mars orbit. The diagram does not include missions that are en route to Mars, or probes that have previously performed a fly-by of Mars and moved on. The two probes of the Mars Cube One mission are counted as a single mission.

# data[].attributes.attachment_link.description
The planet Mars has been explored remotely by spacecraft. Probes sent from Earth, beginning in the late 20th century, have yielded a large increase in knowledge about the Martian system, focused primarily on understanding its geology and habitability potential. Engineering interplanetary journeys is complicated and the exploration of Mars has experienced a high failure rate, especially the early attempts.