Reports Detail Mars Rover Clues to Atmosphere's Past

Reports Detail Mars Rover Clues to Atmosphere's Past

July 18, 2013

This picture shows a lab demonstration of the measurement chamber inside the Tunable Laser Spectrometer, an instrument that is part of the Sample Analysis at Mars investigation on NASA's Curiosity rover.

Image Credit: 

NASA/JPL-Caltech

Full image and caption

PASADENA, Calif. – A pair of new papers report measurements of the Martian atmosphere's composition by NASA's Curiosity rover, providing evidence about loss of much of Mars' original atmosphere.

Curiosity's Sample Analysis at Mars (SAM) suite of laboratory instruments inside the rover has measured the abundances of different gases and different isotopes in several samples of Martian atmosphere. Isotopes are variants of the same chemical element with different atomic weights due to having different numbers of neutrons, such as the most common carbon isotope, carbon-12, and a heavier stable isotope, carbon-13.

SAM checked ratios of heavier to lighter isotopes of carbon and oxygen in the carbon dioxide that makes up most of the planet's atmosphere. Heavy isotopes of carbon and oxygen are both enriched in today's thin Martian atmosphere compared with the proportions in the raw material that formed Mars, as deduced from proportions in the sun and other parts of the solar system. This provides not only supportive evidence for the loss of much of the planet's original atmosphere, but also a clue to how the loss occurred.

"As atmosphere was lost, the signature of the process was embedded in the isotopic ratio," said Paul Mahaffy of NASA Goddard Space Flight Center, Greenbelt, Md.  He is the principal investigator for SAM and lead author of one of the two papers about Curiosity results in the July 19 issue of the journal Science.

Other factors also suggest Mars once had a much thicker atmosphere, such as evidence of persistent presence of liquid water on the planet's surface long ago even though the atmosphere is too scant for liquid water to persist on the surface now. The enrichment of heavier isotopes measured in the dominant carbon-dioxide gas points to a process of loss from the top of the atmosphere -- favoring loss of lighter isotopes -- rather than a process of the lower atmosphere interacting with the ground.

Curiosity measured the same pattern in isotopes of hydrogen, as well as carbon and oxygen, consistent with a loss of a substantial fraction of Mars' original atmosphere. Enrichment in heavier isotopes in the Martian atmosphere has previously been measured on Mars and in gas bubbles inside meteorites from Mars. Meteorite measurements indicate much of the atmospheric loss may have occurred during the first billion years of the planet's 4.6-billion-year history. The Curiosity measurements reported this week provide more precise measurements to compare with meteorite studies and with models of atmospheric loss.

The Curiosity measurements do not directly measure the current rate of atmospheric escape, but NASA's next mission to Mars, the Mars Atmosphere and Volatile Evolution Mission (MAVEN), will do so. "The current pace of the loss is exactly what the MAVEN mission now scheduled to launch in November of this year is designed to determine," Mahaffy said.

The new reports describe analysis of Martian atmosphere samples with two different SAM instruments during the initial 16 weeks of the rover's mission on Mars, which is now in its 50th week. SAM's mass spectrometer and tunable laser spectrometer independently measured virtually identical ratios of carbon-13 to carbon-12. SAM also includes a gas chromatograph and uses all three instruments to analyze rocks and soil, as well as atmosphere.

"Getting the same result with two very different techniques increased our confidence that there's no unknown systematic error underlying the measurements," said Chris Webster of NASA's Jet Propulsion Laboratory, Pasadena, Calif. He is the lead scientist for the tunable laser spectrometer and the lead author for one of the two papers. "The accuracy in these new measurements improves the basis for understanding the atmosphere's history."

Curiosity landed inside Mars' Gale Crater on Aug. 6, 2012 Universal Time (on Aug. 5 PDT). The rover this month began a drive of many months from an area where it found evidence for a past environment favorable for microbial life, toward a layered mound, Mount Sharp, where researchers will seek evidence about how the environment changed.   

More information about Curiosity is online at: http://www.nasa.gov/msl and http://mars.jpl.nasa.gov/msl/ .

You can follow the mission on Facebook at: http://www.facebook.com/marscuriosity and on Twitter athttp://www.twitter.com/marscuriosity .

Guy Webster  818-354-6278
Jet Propulsion Laboratory, Pasadena, Calif.

In the Zone: How Scientists Search for Habitable Planets

In the Zone: How Scientists Search for Habitable Planets

There is only one planet we know of, so far, that is drenched with life. That planet is Earth, as you may have guessed, and it has all the right conditions for critters to thrive on its surface. Do other planets beyond our solar system, called exoplanets, also host life forms?

In the Zone: How Scientists Search for Habitable Planets

In the Zone: How Scientists Search for Habitable Planets

July 17, 2013

This artist's concept shows a Super Venus planet on the left, and a Super Earth on the right. Image credit: NASA/JPL-Caltech/Ames

Full image and caption

There is only one planet we know of, so far, that is drenched with life. That planet is Earth, as you may have guessed, and it has all the right conditions for critters to thrive on its surface. Do other planets beyond our solar system, called exoplanets, also host life forms?

Astronomers still don't know the answer, but they search for potentially habitable planets using a handful of criteria. Ideally, they want to find planets just like Earth, since we know without a doubt that life took root here. The hunt is on for planets about the size of Earth that orbit at just the right distance from their star – in a region termed the habitable zone.

NASA's Kepler mission is helping scientists in the quest to find these worlds, sometimes called Goldilocks planets after the fairy tale because they orbit where conditions are "just right" for life. Kepler and other telescopes have confirmed a handful so far, all of which are a bit larger than Earth -- the Super Earths. The search for Earth's twin, a habitable-zone planet as small as Earth, is ongoing.

An important part of this research is the continuing investigation into exactly where a star's habitable zone starts and stops.

The habitable zone is the belt around a star where temperatures are ideal for liquid water -- an essential ingredient for life as we know it -- to pool on a planet's surface. Earth lies within the habitable zone of our star, the sun. Beyond this zone, a planet would probably be too cold and frozen for life (though it's possible life could be buried underneath a moon's surface). A planet lying between a star and the habitable zone would likely be too hot and steamy.

That perfect Goldilocks planet within the zone wouldn't necessarily be home to any furry creatures. But it would have the potential for some type of life to abound, if even microbes.

In one new study, researchers based at NASA's Exoplanet Science Institute at the California Institute of Technology, in Pasadena, Calif., carefully analyzed the location of both a planet called Kepler-69c and its habitable zone. Their analysis shows that this planet, which is 1.7 times the size of Earth, lies just outside the inner edge of the zone, making it more of a Super Venus than a Super Earth, as previous estimates indicated.

"On the way to finding Earths, Kepler is telling us a lot about the frequency of Venus-like planets in our galaxy," said Stephen Kane, lead author of the new paper on Kepler-69c appearing in the Astrophysical Journal Letters.

To determine the location of a star’s habitable zone, one must first learn how much total radiation it emits. Stars more massive than our sun are hotter, and blaze with radiation, so their habitable zones are farther out. Similarly, stars that are smaller and cooler sport tighter belts of habitability than our sun. For example, the Super Earth planet called Kepler-62f, discovered by Kepler to orbit in the middle of a habitable zone around a cool star, orbits closer to its star than Earth. The planet takes just 267 days to complete an orbit, as compared to 365 days for Earth.

Knowing precisely how far away a habitable zone needs to be from a star also depends on chemistry. For example, molecules in a planet's atmosphere will absorb a certain amount of energy from starlight and radiate the rest back out. How much of this energy is trapped can mean the difference between a turquoise sea and erupting volcanoes.

Researchers led by Ravi kumar Kopparapu of Penn State University, University Park, Pa., used this type of chemical information to nudge the habitable zone out a bit farther than previously thought. The team's 2013 Astrophysical Journal study is the current gold standard in determining how a star's total radiation output relates to the location of its habitable zone. Kane and his colleagues used this information to fine-tune the boundaries of Kepler-69c's habitable zone, in addition to careful measurements of the star's total energy output and the orbit of the planet.

"Understanding the properties of the star is critical to determining planetary properties and calculating the extent of the habitable zone in that system," said Kane.

But before you purchase real estate in a habitable zone, keep in mind there are other factors that dictate whether a world develops lush greenery and beaches. Eruptions from the surfaces of stars called flares, for example, can wreak havoc on planets.

"There are a lot of unanswered questions about habitability," said Lucianne Walkowicz, a Kepler science team member based at Princeton University, N.J., who studies flaring stars. "If the planet gets zapped with radiation all the time by flares from its parent star, the surface might not be a very pleasant place to live. But on the other hand, if there's liquid water around, that makes a really good shield from high-energy radiation, so maybe life could thrive in the oceans."

Flares can also scrape off the atmospheres of planets, complicating the picture further. This is particularly true for the smaller, cooler stars, which tend to be more hyperactive than stars like our sun.

Ideally, astronomers would like to know more about the atmosphere of potentially habitable planets. That way they could look at the planet's molecular makeup for signs of runaway greenhouse gases that could indicate an inhospitable Venus-like planet. Or, future space telescopes might even be able to pick up signatures of oxygen, water, carbon dioxide and methane -- indicators that the planet might be somebody's home.

NASA's upcoming James Webb Space Telescope will bring us closer to this goal, by probing the atmospheres of planets, some of which may lie in habitable zones. The mission won't be able to examine the atmospheres of planets as small as Earth, so we'll have to wait for another future telescope to separate out the Venuses from the Earths.

NASA Ames manages Kepler's ground system development, mission operations and science data analysis. NASA's Jet Propulsion Laboratory in Pasadena, Calif., managed Kepler mission development. Ball Aerospace & Technologies Corp. in Boulder, Colo., developed the Kepler flight system and supports mission operations with JPL at the Laboratory for Atmospheric and Space Physics at the University of Colorado in Boulder. The Space Telescope Science Institute in Baltimore archives, hosts and distributes the Kepler science data. Kepler is NASA's 10th Discovery Mission and is funded by NASA's Science Mission Directorate at the agency's headquarters in Washington.

More information about the Kepler mission is at http://www.nasa.gov/kepler .

More information about exoplanets and NASA's planet-finding program is at http://planetquest.jpl.nasa.gov .

Whitney Clavin 818-354-4673

July 17, 2013

This artist's concept shows a Super Venus planet on the left, and a Super Earth on the right. Image credit: NASA/JPL-Caltech/Ames

Full image and caption

There is only one planet we know of, so far, that is drenched with life. That planet is Earth, as you may have guessed, and it has all the right conditions for critters to thrive on its surface. Do other planets beyond our solar system, called exoplanets, also host life forms?

Astronomers still don't know the answer, but they search for potentially habitable planets using a handful of criteria. Ideally, they want to find planets just like Earth, since we know without a doubt that life took root here. The hunt is on for planets about the size of Earth that orbit at just the right distance from their star – in a region termed the habitable zone.

NASA's Kepler mission is helping scientists in the quest to find these worlds, sometimes called Goldilocks planets after the fairy tale because they orbit where conditions are "just right" for life. Kepler and other telescopes have confirmed a handful so far, all of which are a bit larger than Earth -- the Super Earths. The search for Earth's twin, a habitable-zone planet as small as Earth, is ongoing.

An important part of this research is the continuing investigation into exactly where a star's habitable zone starts and stops.

The habitable zone is the belt around a star where temperatures are ideal for liquid water -- an essential ingredient for life as we know it -- to pool on a planet's surface. Earth lies within the habitable zone of our star, the sun. Beyond this zone, a planet would probably be too cold and frozen for life (though it's possible life could be buried underneath a moon's surface). A planet lying between a star and the habitable zone would likely be too hot and steamy.

That perfect Goldilocks planet within the zone wouldn't necessarily be home to any furry creatures. But it would have the potential for some type of life to abound, if even microbes.

In one new study, researchers based at NASA's Exoplanet Science Institute at the California Institute of Technology, in Pasadena, Calif., carefully analyzed the location of both a planet called Kepler-69c and its habitable zone. Their analysis shows that this planet, which is 1.7 times the size of Earth, lies just outside the inner edge of the zone, making it more of a Super Venus than a Super Earth, as previous estimates indicated.

"On the way to finding Earths, Kepler is telling us a lot about the frequency of Venus-like planets in our galaxy," said Stephen Kane, lead author of the new paper on Kepler-69c appearing in the Astrophysical Journal Letters.

To determine the location of a star’s habitable zone, one must first learn how much total radiation it emits. Stars more massive than our sun are hotter, and blaze with radiation, so their habitable zones are farther out. Similarly, stars that are smaller and cooler sport tighter belts of habitability than our sun. For example, the Super Earth planet called Kepler-62f, discovered by Kepler to orbit in the middle of a habitable zone around a cool star, orbits closer to its star than Earth. The planet takes just 267 days to complete an orbit, as compared to 365 days for Earth.

Knowing precisely how far away a habitable zone needs to be from a star also depends on chemistry. For example, molecules in a planet's atmosphere will absorb a certain amount of energy from starlight and radiate the rest back out. How much of this energy is trapped can mean the difference between a turquoise sea and erupting volcanoes.

Researchers led by Ravi kumar Kopparapu of Penn State University, University Park, Pa., used this type of chemical information to nudge the habitable zone out a bit farther than previously thought. The team's 2013 Astrophysical Journal study is the current gold standard in determining how a star's total radiation output relates to the location of its habitable zone. Kane and his colleagues used this information to fine-tune the boundaries of Kepler-69c's habitable zone, in addition to careful measurements of the star's total energy output and the orbit of the planet.

"Understanding the properties of the star is critical to determining planetary properties and calculating the extent of the habitable zone in that system," said Kane.

But before you purchase real estate in a habitable zone, keep in mind there are other factors that dictate whether a world develops lush greenery and beaches. Eruptions from the surfaces of stars called flares, for example, can wreak havoc on planets.

"There are a lot of unanswered questions about habitability," said Lucianne Walkowicz, a Kepler science team member based at Princeton University, N.J., who studies flaring stars. "If the planet gets zapped with radiation all the time by flares from its parent star, the surface might not be a very pleasant place to live. But on the other hand, if there's liquid water around, that makes a really good shield from high-energy radiation, so maybe life could thrive in the oceans."

Flares can also scrape off the atmospheres of planets, complicating the picture further. This is particularly true for the smaller, cooler stars, which tend to be more hyperactive than stars like our sun.

Ideally, astronomers would like to know more about the atmosphere of potentially habitable planets. That way they could look at the planet's molecular makeup for signs of runaway greenhouse gases that could indicate an inhospitable Venus-like planet. Or, future space telescopes might even be able to pick up signatures of oxygen, water, carbon dioxide and methane -- indicators that the planet might be somebody's home.

NASA's upcoming James Webb Space Telescope will bring us closer to this goal, by probing the atmospheres of planets, some of which may lie in habitable zones. The mission won't be able to examine the atmospheres of planets as small as Earth, so we'll have to wait for another future telescope to separate out the Venuses from the Earths.

NASA Ames manages Kepler's ground system development, mission operations and science data analysis. NASA's Jet Propulsion Laboratory in Pasadena, Calif., managed Kepler mission development. Ball Aerospace & Technologies Corp. in Boulder, Colo., developed the Kepler flight system and supports mission operations with JPL at the Laboratory for Atmospheric and Space Physics at the University of Colorado in Boulder. The Space Telescope Science Institute in Baltimore archives, hosts and distributes the Kepler science data. Kepler is NASA's 10th Discovery Mission and is funded by NASA's Science Mission Directorate at the agency's headquarters in Washington.

More information about the Kepler mission is at http://www.nasa.gov/kepler .

More information about exoplanets and NASA's planet-finding program is at http://planetquest.jpl.nasa.gov .

Whitney Clavin 818-354-4673