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Composition of the Martian Lower Atmosphere

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Composition of the Martian Lower Atmosphere

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A beautiful infographic

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We're heading out of this world for today's post, to examine the atmospheric compositions of the other planets in the solar system, as well as our own. Practically every other planet in our solar system can be considered to have an atmosphere, apart from perhaps the extremely thin, transient atmosphere of Mercury, with the compositions varying from planet to planet. Different conditions on different planets can also give rise to particular effects.
Mercury
Mercury doesn't really have an atmosphere in the strictest sense of the word - its incredibly thin atmosphere is estimated to be over a trillion times thinner than Earth's. Its gravity is about 38% that of Earth, so it isn't capable of retaining much of an atmosphere, and in addition, its proximity to the sun means that the solar wind can carry gases away from the surface. Particles from the solar wind, coupled with the vapourisation of surface rock as a result of meteor impacts, are probably the largest contributors to Mercury's atmosphere.
Venus
Venus is similar to Earth in several respects: its density, size, mass, and volume are all comparable. The atmosphere is where the similarities end, however. The atmospheric pressure is around 92 times that found at sea level on Earth, with the main gas being carbon dioxide - the result of previous volcanic eruptions on the planet's surface. Higher in the atmosphere, the planet also has clouds which are a mixture of sulfur dioxide and sulfuric acid. There is a thick layer of carbon dioxide below these clouds, which subjects the surface of the planet to an intense greenhouse effect. Surface temperature on Venus is around 480˚C - much too hot to sustain life as we know it.
Earth
Earth's atmosphere is composed primarily of nitrogen and oxygen, which are essential for the life which inhabits the planet. The composition of the atmosphere is a direct consequence of the plant life. Plants take in carbon dioxide and expel oxygen through photosynthesis, and without them doing so, it's likely that the percentage of carbon dioxide in the atmosphere would be significantly higher.

The greenhouse effect that carbon dioxide is partially responsible for is the result of molecules of greenhouse gases absorbing infrared radiation, which is re-radiated towards the surface of the planet and surrounding atmosphere. Without this natural warming effect, temperatures on Earth would be significantly lower worldwide. The greenhouse effect is not the same as global warming - this is the intensification of the natural greenhouse effect via the emission of further greenhouse gases into the atmosphere by human activities. Venus is an extreme example of the runaway consequences of increased global warming!
Mars
The atmosphere of Mars is, much like Venus, composed primarily of carbon dioxide. Having mentioned the extreme greenhouse effect present on Venus as a consequence of the high carbon dioxide levels, it may seem puzzling that the surface temperature of Mars reaches a maximum of 35˚C. This is because the atmosphere of Mars is significantly thinner than that of Venus, so although the proportion of carbon dioxide is comparable, the actual concentration is much lower. The dustiness of the atmosphere gives Mars its characteristic appearance.
Jupiter
Jupiter is the first of the gas giants, and the largest planet in the solar system. Its atmosphere is, interestingly, fairly similar to the composition of the Sun. Unlike the inner planets, there isn't a clear point at which the atmosphere of Jupiter stops, and the liquid interior of the planet begins. Around a third of the way towards the planet's core, the pressure is high enough for hydrogen to exist as a metallic liquid, which can conduct electricity and is responsible for Jupiter's electromagnetic field. Jupiter's banded cloud system contains varying amounts of ammonia, water, and ammonia-sulfur compound clouds, and also complex sulfur, phosphorous and carbon compounds.
Saturn
Much like Jupiter, the upper clouds in Saturn's atmosphere are thought to be composed mainly of ammonia ice, with clouds of ammonia hydrosulfide and water lower down. The sulfur present in the atmosphere gives a pale yellow hue to the ammonia clouds. Although not present on the graphic, Saturn's moon Titan has possibly the most intriguing atmosphere in the solar system, which is the only nitrogen rich atmosphere outside of Earth's. It's the only other body in the solar system on which stable surface liquid has ben confirmed, as well as the only other body where it rains - though the rain is liquid methane, rather than water, and it's estimated there are centuries between each rainfall at specific locations on the surface.
Uranus
The atmosphere of Uranus is, like Jupiter and Saturn, mostly hydrogen and helium. However, the slightly higher levels of methane, particularly in the upper atmosphere, cause greater absorption of red light from the sun, in turn causing the planet to appear a blue-cyan colour. Uranus has the coldest atmosphere in the solar system, at approximately -224˚C, and its atmosphere contains much more water ice than Jupiter and Saturn as a consequence of this.
Neptune
As with Uranus, the blue colouration of Neptune is partially a consequence of the presence of methane - however, as Neptune is a deeper blue, it's thought that some unknown constituent of the atmosphere must also contribute towards the colour. As the stratosphere of Neptune contains more gaseous hydrocarbons than Uranus, its temperature is marginally higher. Neptune is also home to the strongest winds in the solar system, with their speeds potentially as high as 600 metres per second.
EDIT: Pluto
Pluto hasn't been a planet for a fair few years now, but that's no reason to leave it out of the fun. On that note, after posting this, I threw this graphic together, so that Pluto doesn't feel left out in the cold:

EDIT 2: As some have been asking for a version of the graphic including atmospheric pressures of each planet, I've produced a PDF version of the graphic that includes this data. Additionally, as another bonus graphic, here's the atmospheric composition of Titan, where it rains methane every few centuries:

The graphic in this article is licensed under a Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International License. See the site's content usage guidelines.
References & Further Reading

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We're heading out of this world for today's post, to examine the atmospheric compositions of the other planets in the solar system, as well as our own. Practically every other planet in our solar system can be considered to have an atmosphere, apart from perhaps the extremely thin, transient atmosphere of Mercury, with the compositions varying from planet to planet.

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earth :: a global map of wind, weather, and ocean conditions

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See current wind, weather, ocean, and pollution conditions, as forecast by supercomputers, on an interactive animated map. Updated every three hours.

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VENUS Solar System Exploration with NASA

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VENUS Solar System Exploration with NASA

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Venus is the second planet from the Sun and is Earth's closest planetary neighbor. It's one of the four inner, terrestrial (or rocky) planets, and it's often called Earth's twin because it's similar in size and density. These are not identical twins, however - there are radical differences between the two worlds.

Venus has a thick, toxic atmosphere filled with carbon dioxide and it's perpetually shrouded in thick, yellowish clouds of sulfuric acid that trap heat, causing a runaway greenhouse effect. It's the hottest planet in our solar system, even though Mercury is closer to the Sun. Surface temperatures on Venus are about 900 degrees Fahrenheit (475 degrees Celsius) - hot enough to melt lead. The surface is a rusty color and it's peppered with intensely crunched mountains and thousands of large volcanoes. Scientists think it's possible some volcanoes are still active.

Venus has crushing air pressure at its surface - more than 90 times that of Earth - similar to the pressure you'd encounter a mile below the ocean on Earth.

Another big difference from Earth - Venus rotates on its axis backward, compared to most of the other planets in the solar system. This means that, on Venus, the Sun rises in the west and sets in the east, opposite to what we experience on Earth. (It's not the only planet in our solar system with such an oddball rotation - Uranus spins on its side.)

Venus was the first planet to be explored by a spacecraft - NASA's Mariner 2 successfully flew by and scanned the cloud-covered world on Dec. 14, 1962. Since then, numerous spacecraft from the U.S. and other space agencies have explored Venus, including NASA's Magellan, which mapped the planet's surface with radar. Soviet spacecraft made the most successful landings on the surface of Venus to date, but they didn't survive long due to the extreme heat and crushing pressure. An American probe, one of NASA's Pioneer Venus Multiprobes, survived for about an hour after impacting the surface in 1978.

More recent Venus missions include ESA's Venus Express (which orbited from 2006 until 2016) and Japan's Akatsuki Venus Climate Orbiter (orbiting since 2016).

NASA's Parker Solar Probe has made multiple flybys of Venus. On Feb. 9, 2022, NASA announced the spacecraft had captured its f irst visible light images of the surface of Venus from space during its February 2021 flyby.

As Parker Solar Probe flew by Venus in February 2021, its WISPR instrument captured these images, strung into a video, showing the nightside surface of the planet. Credit: NASA/APL/NRL

In June 2021, three new missions to Venus were announced. NASA announced two new missions, and ESA announced one:

VERITAS: NASA's VERITAS, or Venus Emissivity, Radio Science, InSAR, Topography, and Spectroscopy, will be the first NASA spacecraft to explore Venus since the 1990s. The spacecraft will launch no earlier than December 2027. It will orbit Venus, gathering data to reveal how the paths of Venus and Earth diverged, and how Venus lost its potential to be a habitable world.

DAVINCI: NASA's DAVINCI mission will launch in the late 2020s. After exploring the top of Venus's atmosphere, DAVINCI will drop a probe to the surface. On its hour-long descent, the probe will take thousands of measurements and snap up-close images of the surface. The probe may not survive the landing, but if it does, it could provide several minutes of bonus science.

EnVision: ESA has selected EnVision to make detailed observations of Venus. As a key partner in the mission, NASA is providing the Synthetic Aperture Radar, called VenSAR, to make high-resolution measurements of the planet's surface features.

Go Farther

Everything you need to know about Venus.

Venus In Depth

Ten Things to Know About Venus
Pop Culture

Because it's so bright and easy to see in the sky, Venus has played a role in popular culture since ancient times, inspiring writing and song:

It was called the most beautiful star in the sky by Homer, author of "The Iliad" and "The Odyssey" - two of the oldest and most important works in Greek literature.

More recently, Venus became a popular venue for 20th-century science fiction writers, including Edgar Rice Burroughs ("Pirates of Venus," 1934); Arthur C. Clarke ("Before Eden," 1961); and C.S. Lewis ("Perelandra," 1943).

Australian author Shirley Hazzard won the 1980 National Book Critics Circle Award for fiction with her book, "The Transit of Venus," about two orphaned sisters. American author John Gray used the planet and its masculine counterpart to explain relationships in his 1992 book "Men Are From Mars, Women Are From Venus."

A song called "Venus" was teen idol Frankie Avalon's first No. 1 hit when it topped the Billboard Hot 100 chart in 1959. A decade later, a different song called "Venus" by the Dutch rock band Shocking Blue topped the charts in several countries. In 1986, British pop group Bananarama had a No. 1 hit in the U.S. with their cover of the song.

More recently, Venus has been a backdrop for video games such as Transhuman Space, Battlezone, and Destiny. And in the Disney animated film "The Princess and the Frog," Ray the firefly falls in love with Venus, "the evening star," as he has mistaken it for another firefly.

Kid-Friendly Venus

Read More

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Venus is the second planet from the sun and our closest planetary neighbor.

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Mars is a dusty, cold, desert world with a very thin atmosphere.

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The Universe: Wildest Weather Moments in the Cosmos (S2, E15) | Full Episode | History

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In just two weeks, dust storms have obscured more than 10 million square miles of Mars' southern hemisphere.

The storms forced NASA to suspend operations of its twin Mars rovers. The biggest storm has weakened near the Opportunity rover and thickened near Spirit's location. Both rovers are gathering enough solar energy to survive and observe their surroundings, lead rover scientist Steven Squyres of Cornell University said yesterday.

Such dramatic dust storms, however, aren't the only weather phenomenon Mars has to offer. The red planet hosts clouds of ice and carbon dioxide, tornado-like dust devils, auroras and even complex jet streams--all of this, despite the fact that Mars' atmosphere is less than 1 percent as dense as Earth's.

"Mars has a similar tilt [as] Earth, so it has the same seasons Earth has with a progression of summer, fall, winter and spring," said John Wilson, a planetary scientist who studies Mars' atmosphere at the National Oceanic & Atmospheric Administration in Princeton, New Jersey.

Although planetary scientists have yet to develop a predictive model for Martian weather, Wilson noted that 43 years of Mars exploration have helped reveal the planet's curious weather trends.
Dusty summers
When Mars tilts away from the sun, its "hot" summers begin in the southern hemisphere.

"During the summer, it can be as warm as a day in the tropics, as high as 80 degrees Fahrenheit," Wilson said. Martian nights, however, are blisteringly cold and can reach -180 degrees Fahrenheit. Such bone-chilling temperatures can contract and snap the soldered metal joints of unheated electronic circuit boards-- an imminent threat to any mission to Mars.

Wilson explained that southern summers are the most likely period for dust devils to occur, thanks to dramatic temperature shifts. When the sun warms the cold ground, hot air quickly rises and pulls in surrounding air--and microscopic dust particles with it.

"A billion years of wind erosion [have] created really fine dust on Mars, and the absence of water prevents it from cementing it back together like it does on Earth," Wilson said. Once the dust devils get going, they can whip up the ultra-fine dust to about 70 mph.

Planetary scientists think the dusty tornadoes, when persistent and large enough, are responsible for creating light-drowning global dust storms, as they seem to do every three Martian years (about six Earth years).
Whispy clouds
Icy clouds of carbon dioxide have also been seen by Mars orbiters from space and by the Mars Exploration Rovers from the ground.

"Near the peaks of volcanoes, you can regularly see clouds on Mars," Wilson said. "They also form in the northern hemisphere when the planet is far away from the sun. They're like cirrus clouds on Earth and float at a very high altitude."

The clouds are especially persistent above the poles where they're fed by carbon dioxide evaporating off the surface of ice caps made of the frozen gas. High- and low-pressure fronts and jet streams move the clouds around, just as on Earth.
Dry variety
"There's not a lot of atmosphere on Mars, but enough to create storm systems that move across the planet," Wilson said, though the storms in question are made of dust--not water vapor.

Wilson explained Mars would have a lot more variety in its weather if liquid water were present.

"Other than being sunny and windy, there's not a whole lot happening on Mars, though the weather we do see is similar to Earth's," Wilson said. "The key is a lack of water vapor, which on Earth fuels hurricanes, rain and so many other things we see."

Perhaps deep in Mars' past, however, as recent evidence suggests, there may have been oceans driving the same wet weather currently found on Earth.

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In just two weeks, dust storms have obscured more than 10 million square miles of Mars' southern hemisphere. The storms forced NASA to suspend operations of its twin Mars rovers. The biggest storm has weakened near the Opportunity rover and thickened near Spirit's location.