Most of Mars’ atmosphere was lost to space

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Most of Mars' atmosphere was lost to space
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)

Solar wind and radiation are responsible for stripping the Martian atmosphere, transforming Mars from a planet that could have supported life billions of years ago into a frigid desert world, according to new results from NASA’s MAVEN spacecraft.

“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.

In 2015, MAVEN team members previously announced results that showed atmospheric gas is being lost to space today and described how atmosphere is stripped away.

The present analysis uses measurements of today’s atmosphere for the first estimate of how much gas was lost through time.

Liquid water, essential for life, is not stable on Mars’ surface today because the atmosphere is too cold and thin to support it.

However, evidence such as features resembling dry riverbeds and minerals that only form in the presence of liquid water indicates the ancient Martian climate was much different – warm enough for water to flow on the surface for extended periods.

“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 many ways a planet can lose some of its atmosphere. For example, chemical reactions can lock gas away in surface rocks, or an atmosphere can be eroded by radiation and a stellar wind from a planet’s parent star.

The new result reveals that solar wind and radiation were responsible for most of the atmospheric loss on Mars, and the depletion was enough to transform the Martian climate.

The solar wind is a thin stream of electrically conducting gas constantly blowing out from the surface of the sun.

The early Sun had far more intense ultraviolet radiation and solar wind, so atmospheric loss by these processes was likely much greater in Mars’ history.

According to the team, these processes may have been the dominant ones controlling the planet’s climate and habitability.

It’s possible microbial life could have existed at the surface early in Mars’ history. As the planet cooled off and dried up, any life could have been driven underground or forced into rare surface oases.

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News source: NASA. The content is edited for length and style purposes.
Figure legend: This Knowridge.com image is credited to NASA’s Goddard Space Flight Center.