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Most of Mars’ atmosphere lost to space, scientists say

This artist’s concept depicts the early Martian environment (right) – believed to contain liquid water and a thicker atmosphere – versus the cold, dry environment seen at Mars today (left). NASA's Mars Atmosphere and Volatile Evolution is in orbit of the Red Planet to study its upper atmosphere, ionosphere and interactions with the sun and solar wind.  Image Credit: NASA’s Goddard Space Flight Center

This artist’s concept depicts the early Martian environment (right) – believed to contain liquid water and a thicker atmosphere – versus the cold, dry environment seen at Mars today (left). NASA’s Mars Atmosphere and Volatile Evolution is in orbit of the Red Planet to study its upper atmosphere, ionosphere, and interactions with the Sun and solar wind. Caption and Image Credit: NASA’s Goddard Space Flight Center

According to a new study by scientists working with NASA’s MAVEN spacecraft, the Martian atmosphere was mostly stripped away by solar wind and radiation, changing Mars from a world that could have supported life billions of years ago into the frigid desert planet it is today. 

“We’ve determined that most of the gas ever present in the Mars atmosphere has been lost to space,” said Bruce Jakosky, principal investigator for the Mars Atmosphere and Volatile Evolution Mission (MAVEN), University of Colorado in Boulder.

The team made this determination from the latest results, which reveal that about 65 percent of the argon that was ever in the atmosphere has been lost to space. Jakosky is the lead author of a paper on this research published March 31, 2017, in Science.

In 2015, members of the MAVEN team announced findings that indicated atmospheric gas is being lost into space today and described how it is being stripped away. The new study used measurements of the current Martian atmosphere to estimate how much gas has been lost over time.

Liquid water, which is essential to sustain life, is not stable on the Martian surface today because the atmosphere is too thin and cold to support it. Evidence found on Mars, such as features resembling dry riverbeds and minerals that form only in the presence of liquid water, suggest the ancient Martian environment was once warm enough for water to flow on the surface for an extended period.

“This discovery is a significant step toward unraveling the mystery of Mars’ past environments,” said Elsayed Talaat, MAVEN Program Scientist, at NASA Headquarters in Washington. “In a broader context, this information teaches us about the processes that can change a planet’s habitability over time.”

There are several ways a planet could lose part of its atmosphere. Chemical reactions could lock gas within surface rocks or the atmosphere could be eroded by radiation and the stellar wind of the star it orbits.

This new study indicates solar wind, a thin stream of electrically conducting gas blowing out from the surface of the Sun, and radiation were responsible for most of the atmospheric loss on Mars.

Jakosky and his colleagues measured the atmospheric abundance of two different isotopes of argon gas. Isotopes are atoms of the same elements with different masses. Because the lighter of the two isotopes escapes into space more readily, it leaves the gas remaining behind enriched in the heavier isotope.

The researchers used the relative abundance of the two argon isotopes measured in the upper atmosphere and the surface to estimate the fraction of the atmosphere that had been lost into space.

This infographic shows how Mars lost argon and other gasses over time due to ‘sputtering.’ Image Credit: NASA’s Goddard Space Flight Center

This infographic shows how Mars lost argon and other gasses over time due to ‘sputtering.’ Caption and Image Credit: NASA’s Goddard Space Flight Center

Argon is a “noble gas” and cannot react chemically and cannot be sequestrated in rocks. Only a physical process called “sputtering” can remove argon into space.

In sputtering, ions picked up by solar wind can impact Mars at high speeds and physically knock atmospheric gas into space. The scientists tracked argon because it could only be removed from the atmosphere by sputtering.

After determining the amount of argon lost due to sputtering, the researchers were able to use this information to determine the sputtering loss of other gasses, including carbon dioxide

Carbon dioxide is of interest to the researchers because it is the most plentiful gas in the Martian atmosphere and because it is a greenhouse gas that can retain heat and warm the planet.

“We determined that the majority of the planet’s [carbon dioxide] was also lost to space by sputtering,” said Jakosky. “There are other processes that can remove [carbon dioxide], so this gives the minimum amount of [carbon dioxide] that’s been lost to space.”

The team based its estimate on upper atmosphere data collected by MAVEN’s Neutral Gas and Ion Mass Spectrometer (NGIMS) and surface measurements made by NASA’s Sample Analysis at Mars (SAM) on board the Curiosity rover.

“The combined measurements enable a better determination of how much Martian argon has been lost to space over billions of years,” said Paul Mahaffy of NASA’s Goddard Space Flight Center in Greenbelt, Maryland. “Using measurements from both platforms points to the value of having multiple missions that make complementary measurements.”

Mahaffy, a co-author of the paper, is the principal investigator on the SAM instrument and lead on the NGIMS instrument, both of which were developed at NASA Goddard.

Video courtesy of NASA


Jim Sharkey is a lab assistant, writer and general science enthusiast who grew up in Enid, Oklahoma, the hometown of Skylab and Shuttle astronaut Owen K. Garriott. As a young Star Trek fan he participated in the letter-writing campaign which resulted in the space shuttle prototype being named Enterprise. While his academic studies have ranged from psychology and archaeology to biology, he has never lost his passion for space exploration. Jim began blogging about science, science fiction and futurism in 2004. Jim resides in the San Francisco Bay area and has attended NASA Socials for the Mars Science Laboratory Curiosity rover landing and the NASA LADEE lunar orbiter launch.

Reader Comments

I feel the Sun is causing Planet Earth its atmospheric problems as well. We may be doomed as our planet becomes a cinder.

What if in the big time scheme of things (we have been here in just a moment in the time of our planet, a few seconds on the the time clock of life on earth) Mars was capable of life and moved out of the zone of the purposed ideal conditions of as life sustainable planet and our planet is destined to do the same. So much time has passed since life originally was on this planet that maybe just maybe both planets had life at some point but because Mars moved just enough from the sun that life stopped.just a theory.

interesting but i also think that biological processes in the past martian environment like Earth had extinction level events caused by extreme geological and asteroid and comet impacts and finally luck ran out and the atmospheric processing of biological cellular breakdown of chemicals ceased to function in a big way and remained lifeless and never recovered fully


This is what happens when the magnetosphere dies. Radioactivity in the core only lasts so long.

You are doomed. Stupid humans.


What I’m thinking is why are we going to spend TRILLIONS on a mission to colonize Mars. What could all those resources accomplish on our own planet? Seems like very expensive bragging rights to me. Sci-fi is great; I love it. Is it possible that Mars just isn’t massive enough to sustain an atmosphere and therefore never has and never will? If it were more massive it should have been able to hold on to it’s atmosphere as well as its auroras. What looks like water channels could have been caused by anything. Seems we’re just barely figuring out our own geological processes so how could we hope to Theorize ancient Martian geological activity?

Maybe mars can be our field test for restructuring other celestial bodies for us to populate in the future?
Seems like an excellent lab to learn some of all that much to be learned……

Mars has less than half the gravitational pull as Earth. What if a solar wind 2X happens, or even 1X, could we lose some or all our aptmosphere? That kind of worries me. Maybe some people should keep studying this. The chances may not be that high but we do have 7+ billion people who may be affected and most aren’t doing very important work anyway. Some could spend less time on making self driving cars or virtual reality games and spend some time on this. I’m happy if they take some of my tax money for that.

Terence McClelland

A key assumption not discussed is the baseline ratio of argon isotopes. And the actual values are simply unknowable.

I thought that Mars lost its atmosphere when it lots its magnetic field. There was a program on PBS, I think, about it. “Sweet Magnetic Field”

Trump and a bunch of very wealthy people want us to go there. There must be mineral wealth, or something.

Rick Bertolett

Blackjack and hookers are what trumps after

Our magnetic field helps to shield us from the solar wind. The field itself interacts with the solar wind ions causing a kind of cosmic force field. The aurora borealis is a direct result of the eddy caused at the polls. Mars magnetic field is significantly weaker than earths and if memory serves it’s core doesn’t have the spin characteristics that the earth does resulting in strong polls along the axis of rotation. The info here just supports that theory.

Yeah, and what about the huge 2,300 km diameter crater on Mars, you know, Hellas Planitia? Might have something to do with there being just 7 millibar of pressure on the surface of Mars?

Venus has 92 bar of atmospheric pressure and is half the distance to the Sun than Earth, or 1/4 the distance to the Sun than Mars. IF the Solar Wind stripped Mars of it’s atmosphere then how do you account for Venus? It doesn’t pass the smell test.

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