Scientists with NASA's Mars Atmosphere and Volatile Evolution (MAVEN) mission may have determined what may have caused Mars to transition from a warm and wet planet to a freezing and barren wasteland.
New MAVEN data allowed a team of researchers to determine the rate at which the Red Planet is currently losing gas, which is being stripped away by violent solar winds. They found the atmosphere eroded much more dramatically during solar storms.
"Mars appears to have had a thick atmosphere warm enough to support liquid water which is a key ingredient and medium for life as we currently know it," said John Grunsfeld, astronaut and associate administrator for the NASA Science Mission Directorate in Washington. "Understanding what happened to the Mars atmosphere will inform our knowledge of the dynamics and evolution of any planetary atmosphere. Learning what can cause changes to a planet's environment from one that could host microbes at the surface to one that doesn't is important to know, and is a key question that is being addressed in NASA's journey to Mars."
These findings suggest Mars' atmosphere was eroded even more significantly when the Sun was younger and more vibrant billions of years ago. This erosion has built up over time, creating the Mars we see today. Additionally, a number of strong solar storms hit the Red Planet in March 2015, accelerating the loss of atmosphere. The researchers believe the loss is experienced in three different regions: down the "tail," where solar wind flows behind the planet; above the Martian poles in a "polar plume"; and from a gas cloud surrounding the planet. About 75 percent of the escaping ions are originate in the tail region, and 25 percent come from the plume.
Evidence suggests Mars was once abundant with water, and we can still see valleys carved by rivers and water-related mineral deposits there today. In order for water to exist, Mars' atmosphere would have needed to be much denser.
"Solar-wind erosion is an important mechanism for atmospheric loss, and was important enough to account for significant change in the Martian climate," said Joe Grebowsky, MAVEN project scientist from NASA's Goddard Space Flight Center in Greenbelt, Maryland. "MAVEN also is studying other loss processes -- such as loss due to impact of ions or escape of hydrogen atoms -- and these will only increase the importance of atmospheric escape."