MAVEN Measures Mars' Atmosphere Loss
Solar wind and radiation are responsible for stripping the Martian atmosphere, according to results from NASA's MAVEN spacecraft. By measuring light and heavy isotopes of argon in the Martian atmosphere, scientists have determined that the majority of the noble gas was removed from the planet by "sputtering." In this process, ions get picked up by the solar wind and slammed into other atoms at the top of the atmosphere, knocking them into space. Over billions of years, sputtering removed about 65% of the planet's argon – along with other gases like carbon dioxide and water vapor – helping to transform Mars from a more hospitable planet into the cold, dry world that we see today.