NASA's MAVEN reveals 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). 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. (Courtesy: NASA’s Goddard Space Flight Center)

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. Jakosky is lead author of a paper on this research to be published in Science on Friday, March 31.

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.