Infographic explaining the MAVEN argon results. Enlarge or click "download" for print-resolution versions. Also available in text-readable PDF for the visually impaired.
Solar wind and radiation are responsible for stripping the Martian atmosphere, according to results from NASA's MAVEN mission. By measuring light and heavy isotopes of argon in the Martian atmosphere, scientists have determined that the majority of the planet's air and water were removed to space by sputtering. In this process, ions from the Mars atmosphere get picked up by the solar wind and slammed into other atoms at the top of the atmosphere, knocking them into space.
Scientists used measurements of light and heavy argon from MAVEN and NASA's Curiosity rover to determine that sputtering has removed 65% of Mars' argon to space, along with the majority of other gases like carbon dioxide. Over billions of years, this transformed Mars from a hospitable environment into the cold, dry planet that we see today. Learn more about the MAVEN argon loss finding.