High above the thin Martian skies, the MAVEN spacecraft is carrying out a mission: determine how Mars lost its early atmosphere, and with it, its water.
MAVEN is currently executing the 9th stellar occultation campaign of the mission. These campaigns involve the IUVS instrument using the light from a setting star as it passes through Mars’ atmosphere to look for subtle changes in its color as it dips through the limb of Mars.
Such stellar occultations reveal what Mars’ atmosphere is made of, and how its composition varies with altitude. [More at link]