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Possible life on other planets

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Exoplanet Exploration: Planets Beyond our Solar System

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The ultimate goal of NASA's exoplanet program is to find unmistakable signs of current life on a planet beyond Earth. How soon that can happen depends on two unknowns: the prevalence of life in the galaxy and how lucky we get as we take those first, tentative, exploratory steps.

MIT astronomer Sara Seager, is a McArthur Genius Fellow and leader in the scientific race to find another Earth in the near future.

Our early planet finding missions, such as NASA's Kepler and its extended incarnation, K2, or the coming James Webb Space Telescope, could yield bare bones evidence of the potentially habitable worlds. James Webb, designed in part to investigate gas giants and super Earths, might find an outsized version of our planet. NASA's Nancy Grace Roman Space Telescope or the Wide-Field Infrared Survey Telescope, could zero in on a distant planet's reflected light to detect the signatures of oxygen, water vapor, or some other powerful indication of possible life.

But unless we get lucky, the search for signs of life could take decades. Discovering another blue-white marble hidden in the star field, like a sand grain on the beach, will probably require an even larger imaging telescope. Designs are already underway for that next-generation planet finder, to be sent aloft in the 2030s or 2040s.

MIT physics professor Sara Seager looks for possible chemical combinations that could signal the presence of alien life. She and her biochemistry colleagues first focused on the six main elements associated with life on Earth: carbon, nitrogen, oxygen, phosphorous, sulfur and hydrogen.

"We're going to have so few planets, we have to get lucky," Seager said. "I don't want to miss anything. I don't want to miss it because we weren't smart enough to think of some molecule."

To find out how about the advanced, space-based telescope technology being developed at NASA to search for life among the stars, read Inventing the Future

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national aeronautics and space administration

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Is there life on other planets? - Exoplanet Exploration: Planets Beyond our Solar System

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The ultimate goal of NASA's exoplanet program is to find unmistakable signs of current life on a planet beyond Earth. How soon that can happen depends on two unknowns: the prevalence of life in the galaxy and how lucky we get as we take those first, tentative, exploratory steps.

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Another second chance for when we mess up

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NASA Just Discovered a Rare Earth-Sized Planet in a Habitable Zone

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When it comes to finding life outside of our Solar System, planets that closely resemble Earth seem like a good place to start.

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NASA's Transiting Exoplanet Survey Satellite (TESS) has discovered its first Earth-size planet in its star's habitable zone, the range of distances where conditions may be just right to allow the presence of liquid water on the surface. Scientists confirmed the find, called TOI 700 d, using NASA's Spitzer Space Telescope and have modeled the planet's potential environments to help inform future observations.

TOI 700 d is one of only a few Earth-size planets discovered in a star's habitable zone so far. Others include several planets in the TRAPPIST-1 system and other worlds discovered by NASA's Kepler Space Telescope.

"TESS was designed and launched specifically to find Earth-sized planets orbiting nearby stars," said Paul Hertz, astrophysics division director at NASA Headquarters in Washington. "Planets around nearby stars are easiest to follow-up with larger telescopes in space and on Earth. Discovering TOI 700 d is a key science finding for TESS. Confirming the planet's size and habitable zone status with Spitzer is another win for Spitzer as it approaches the end of science operations this January."

TESS monitors large swaths of the sky, called sectors, for 27 days at a time. This long stare allows the satellite to track changes in stellar brightness caused by an orbiting planet crossing in front of its star from our perspective, an event called a transit.

TOI 700 is a small, cool M dwarf star located just over 100 light-years away in the southern constellation Dorado. It's roughly 40% of the Sun's mass and size and about half its surface temperature. The star appears in 11 of the 13 sectors TESS observed during the mission's first year, and scientists caught multiple transits by its three planets.

The star was originally misclassified in the TESS database as being more similar to our Sun, which meant the planets appeared larger and hotter than they really are. Several researchers, including Alton Spencer, a high school student working with members of the TESS team, identified the error.

"When we corrected the star's parameters, the sizes of its planets dropped, and we realized the outermost one was about the size of Earth and in the habitable zone," said Emily Gilbert, a graduate student at the University of Chicago. "Additionally, in 11 months of data we saw no flares from the star, which improves the chances TOI 700 d is habitable and makes it easier to model its atmospheric and surface conditions."

Gilbert and other researchers presented the findings at the 235th meeting of the American Astronomical Society in Honolulu, and three papers - one of which Gilbert led - have been submitted to scientific journals.

The innermost planet, called TOI 700 b, is almost exactly Earth-size, is probably rocky and completes an orbit every 10 days. The middle planet, TOI 700 c, is 2.6 times larger than Earth - between the sizes of Earth and Neptune - orbits every 16 days and is likely a gas-dominated world. TOI 700 d, the outermost known planet in the system and the only one in the habitable zone, measures 20% larger than Earth, orbits every 37 days and receives from its star 86% of the energy that the Sun provides to Earth. All of the planets are thought to be tidally locked to their star, which means they rotate once per orbit so that one side is constantly bathed in daylight.

A team of scientists led by Joseph Rodriguez, an astronomer at the Center for Astrophysics | Harvard & Smithsonian in Cambridge, Massachusetts, requested follow-up observations with Spitzer to confirm TOI 700 d.

"Given the impact of this discovery - that it is TESS's first habitable-zone Earth-size planet - we really wanted our understanding of this system to be as concrete as possible," Rodriguez said. "Spitzer saw TOI 700 d transit exactly when we expected it to. It's a great addition to the legacy of a mission that helped confirm two of the TRAPPIST-1 planets and identify five more."

The Spitzer data increased scientists' confidence that TOI 700 d is a real planet and sharpened their measurements of its orbital period by 56% and its size by 38%. It also ruled out other possible astrophysical causes of the transit signal, such as the presence of a smaller, dimmer companion star in the system.

Rodriguez and his colleagues also used follow-up observations from a 1-meter ground-based telescope in the global Las Cumbres Observatory network to improve scientists' confidence in the orbital period and size of TOI 700 c by 30% and 36%, respectively.

Because TOI 700 is bright, nearby, and shows no sign of stellar flares, the system is a prime candidate for precise mass measurements by current ground-based observatories. These measurements could confirm scientists' estimates that the inner and outer planets are rocky and the middle planet is made of gas.

Future missions may be able to identify whether the planets have atmospheres and, if so, even determine their compositions.

While the exact conditions on TOI 700 d are unknown, scientists can use current information, like the planet's size and the type of star it orbits, to generate computer models and make predictions. Researchers at NASA's Goddard Space Flight Center in Greenbelt, Maryland, modeled 20 potential environments of TOI 700 d to gauge if any version would result in surface temperatures and pressures suitable for habitability.

Their 3D climate models examined a variety of surface types and atmospheric compositions typically associated with what scientists regard to be potentially habitable worlds. Because TOI 700 d is tidally locked to its star, the planet's cloud formations and wind patterns may be strikingly different from Earth's.

One simulation included an ocean-covered TOI 700 d with a dense, carbon-dioxide-dominated atmosphere similar to what scientists suspect surrounded Mars when it was young. The model atmosphere contains a deep layer of clouds on the star-facing side. Another model depicts TOI 700 d as a cloudless, all-land version of modern Earth, where winds flow away from the night side of the planet and converge on the point directly facing the star.

When starlight passes through a planet's atmosphere, it interacts with molecules like carbon dioxide and nitrogen to produce distinct signals, called spectral lines. The modeling team, led by Gabrielle Engelmann-Suissa, a Universities Space Research Association visiting research assistant at Goddard, produced simulated spectra for the 20 modeled versions of TOI 700 d.

"Someday, when we have real spectra from TOI 700 d, we can backtrack, match them to the closest simulated spectrum, and then match that to a model," Engelmann-Suissa said. "It's exciting because no matter what we find out about the planet, it's going to look completely different from what we have here on Earth."

TESS is a NASA Astrophysics Explorer mission led and operated by MIT in Cambridge, Massachusetts, and managed by NASA's Goddard Space Flight Center. Additional partners include Northrop Grumman, based in Falls Church, Virginia; NASA's Ames Research Center in California's Silicon Valley; the Harvard-Smithsonian Center for Astrophysics in Cambridge, Massachusetts; MIT's Lincoln Laboratory; and the Space Telescope Science Institute in Baltimore. More than a dozen universities, research institutes and observatories worldwide are participants in the mission.

The Jet Propulsion Laboratory in Pasadena, California, manages the Spitzer Space Telescope mission for NASA's Science Mission Directorate in Washington. Science operations are conducted at the Spitzer Science Center at Caltech in Pasadena. Space operations are based at Lockheed Martin Space in Littleton, Colorado. Data are archived at the Infrared Science Archive housed at IPAC at Caltech. Caltech manages JPL for NASA.

The modeling work was funded through the Sellers Exoplanet Environments Collaboration at Goddard, a multidisciplinary collaboration that brings together experts to build comprehensive and sophisticated computer models to better analyze current and future exoplanet observations.

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tess (transiting exoplanet survey satellite)

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NASA Planet Hunter Finds its 1st Earth-size Habitable-zone World - NASA

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NASA's Transiting Exoplanet Survey Satellite (TESS) has discovered its first Earth-size planet in its star's habitable zone, the range of distances where

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Enter the Access ID and Passcode provided by your school to access Britannica School.

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Newsela | Astronomers uncover 7 warm, rocky, Earth-like planets 39 light-years away

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Astronomers and astrobiologists are excited to study TRAPPIST-1, an ultracool dwarf star 39 light-years away that has seven potentially Earth-like planets in its orbit.

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Newsela | Water found on temperate planet orbiting distant star: "Super Earth"

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Astronomers have discovered a planet outside our solar system that has water and temperatures suitable for life. The planet is 110 light-years away, so don't try to book a flight just yet.

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Section: News, Pg. 05a

Scientists with NASA announced they have discovered an Earth-sized planet that is likely rocky - and could be habitable.

The planet, named TOI 700 e, is slightly smaller than Earth and orbits a red dwarf star called TOI 700 about 100 light-years away. It's one of four planets to orbit the star, alongside TOI 700 b, c and d.

TOI 700 d already was known to be in the habitable zone, a discovery made possible by NASA's Transiting Exoplanet Survey Satellite (TESS), which monitors large portions of the sky for 27 days at a time to track changes in stellar brightness caused by planets.

But it took more than a year for scientists to discover TOI 700 e and learn that it was within the star's habitable zone. Its discovery was presented at the American Astronomical Society in Seattle, and a paper about the planet was accepted by The Astrophysical Journal Letters.

Also known as the "Goldilocks zone," the habitable zone is the distance from a star where liquid water could exist on an orbiting planet, according to NASA. It gets its nickname because the conditions on the planet are not too cold or too hot to sustain life.

Scientists say TOI 700 e, along with planet d, are in the "optimistic" habitable zone, which means the planet, at some point, could have had liquid water in its history.

"This is one of only a few systems with multiple, small, habitable-zone planets that we know of," Emily Gilbert, a postdoctoral fellow at NASA's Jet Propulsion Laboratory who led the work, said in a statement.

TOI 700 e is about 95% the size of Earth and is probably a rocky planet similar to ours.

It is about 10% smaller than planet d. Although it is the fourth planet to be discovered in the TOI 700 system, it is between planets c and d.

"If the star was a little closer or the planet a little bigger, we might have been able to spot TOI 700 e in the first year of TESS data," said Ben Hord, graduate researcher at NASA's Goddard Space Flight Center.

It takes TOI 700 e about 28 days to orbit its star, and it may also be a tidally locked planet, meaning it spins only once per orbit and only one side always faces the star. It's similar to how only one side of the moon is always facing Earth.

Scientists are constantly discovering planets in habitable zones that could sustain human life.

In September, scientists also using TESS found a "super-Earth" planet about 100 light-years away from us that could host life. In 2019, water vapor was detected in the atmosphere of the planet known as K2-18b, along with temperatures that could support life.

Scientists plan follow-up studies on the TOI 700 system as TESS searches for other systems in the universe.

"We're looking forward to the other exciting discoveries hidden in the mission's treasure trove of data," said Allison Youngblood, a research astrophysicist and TESS deputy project scientist.

(c) USA TODAY, 2023

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NASA finds planet nearly Earth's size in habitable zone

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Section: News, Pg. 05a Scientists with NASA announced they have discovered an Earth-sized planet that is likely rocky - and could be habitable. The planet, named TOI 700 e, is slightly smaller than Earth and orbits a red dwarf star called TOI 700 about 100 light-years away.

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Section:

QUANTUM GRAVITY

WEIGHING IN. When a new is discovered, the phrase "Earth-like" frequently comes up. But it's a bit of a misnomer. We don't know if it's Earth-like at all! Our current instruments fall just short of the ability to direct image or resolve such a small planet, much less tell what's in its atmosphere. Here's a guide to how terms should be used.

A planet is considered Earth-mass when its mass is similar to our own world. That's 1.31660063 × 1025 pounds (5.972 × 1024 kg). Planets between 1 and 5 Earth masses are likely rocky. Those 5 to 10 Earth masses may resemble Neptune. Planets more massive than Earth are often called super-Earths. Mass is measured by watching the tug a planet has on its star.

A planet is considered Earth-size when it is one and a quarter times the radius of Earth or below. Super-Earths are one and a quarter to two times the radius of Earth. Planets called mini-Neptunes, which are likely gaseous instead of rocky, are between two and six times Earth's radius. Neptune is six times the radius of Earth.

So what is Earth-like? A planet not only has to be the same size and the same mass as Earth, but it must have liquid water oceans and a substantial atmosphere. Otherwise, you may have a planet that is more like Venus, Mars, or Mercury, even if it's seemingly in the "right" place. Thus we have found Earth-mass and Earth-size planets but are still searching for something that is actually Earth-like.

FAST FACT

Several known exoplanets have masses similar to Earth, but radii several times bigger, suggesting they are miniature ice giants - mini-Neptunes.

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By J. W.

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SO WHAT'S IN AN EARTH-LIKE PLANET, ANYWAY?

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Section: QUANTUM GRAVITY WEIGHING IN. When a new is discovered, the phrase "Earth-like" frequently comes up. But it's a bit of a misnomer. We don't know if it's Earth-like at all! Our current instruments fall just short of the ability to direct image or resolve such a small planet, much less tell what's in its atmosphere.

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The Sensing the Dynamic Universe (SDU) project creates sonified videos exploring the multitude of celestial variables such as stars, supernovae, quasars, gamma ray bursts and more. We sonify lightcurves and spectra, making the astrophysics of variables and transients accessible to the general public, with particular attention to accessibility for those with visual and/or neurological differences.

SDU Website

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Does life exist outside of the solar system?

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The Sensing the Dynamic Universe (SDU) project creates sonified videos exploring the multitude of celestial variables such as stars, supernovae, quasars, gamma ray bursts and more. We sonify lightcurves and spectra, making the astrophysics of variables and transients accessible to the general public, with particular attention to accessibility for those with visual and/or neurological differences.

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Newsela | Instructional Content Platform

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Newsela is an Instructional Content Platform that supercharges reading engagement and learning in every subject.

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THE TOP 100 SCIENCE STORIES OF 2012

1. ARRIVAL The spacecraft transporting the Curiosity rover entered the Martian atmosphere at 1:10 am EOT on August 6 After an eight-month journey. Because it takes 14 minutes to send or receive a signal from Mars, NASA operators could not communicate with the craft during its descent; they had to hope that their meticulously plotted engineering and software would, within "seven minutes of terror," slow the probe down from 13,000 miles per hour and gently and precisely deposit Curiosity at the selected landing site.

2. DESCENT Friction with Mars's tenuous atmosphere slowed the spacecraft as it descended but created temperatures up to 3,800 degrees Fahrenheit. A heat shield protected the rover inside from incineration. Meanwhile, a network of eight thrusters adjusted the trajectory toward the landing site. At an altitude of about seven miles, with Curiosity traveling at 900 miles per hour, a 50 foot-wide parachute deployed. Twenty-four seconds later, the probe ditched its heat shield and checked speed and altitude using onboard radar.

3. SKYCRANE DROP Just one mile before touchdown, the spacecraft played its trump card: Audacity, a rocket-powered platform designed specifically to shuttle Curiosity to the Martian surface. [Previous Mars rovers had landed with air bags, but the one-ton Curiosity was far too porky for that approach.] Audacity used eight engines to slow to a leisurely 1.7 miles per hour as the rover, connected by a bridle, dangled beneath. Audacity kept dropping until it sensed the rover was stable on the ground. Then it cut itself loose, throttled up its rockets, and flung itself skyward, crash-landing 2,100 feet away. Curiosity arrived in perfect shape, ready to get to work.

ON THE JOB One of Curiosity's first photos was a black-and-white look at its landing site, Gale Crater [left]. In the distance was Mount Sharp, a stratified, 18,000-foot peak that should show how environmental conditions on Mars have changed over time. Curiosity arrived bristling with geology tools, two of which it tested on a football-size rock nicknamed Jake [below]. The rover's ChemCam blasted Jake with a laser [red dots], while its Alpha Particle X-Ray Spectrometer bombarded the rock with radiation [purple circles]. The instruments revealed that Jake is a basaltic rock similar to those found in Hawaii.

LAZY RIVER In September Curiosity found an outcrop of conglomerate rock [left], pebbles and gravel bound together by wet sediment. After years of inferring the existence of ancient water from chemical analyses and satellite photos, this is by far the most direct proof that water once flowed on Mars. Scientists estimate that 4 billion years ago a river up to a few feet deep lazily flowed down from Gale Crater's rim. Curiosity's next task is to determine whether other conditions on ancient Mars, like the chemistry of the soil and air, were also favorable to the development of microbial life.

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By ANDREW GRANT

ILLUSTRATIONS BY RON MILLER

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THE TOP 100 SCIENCE STORIES OF 2012 1. ARRIVAL The spacecraft transporting the Curiosity rover entered the Martian atmosphere at 1:10 am EOT on August 6 After an eight-month journey.

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Newsela | Instructional Content Platform

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Newsela is an Instructional Content Platform that supercharges reading engagement and learning in every subject.