Mars always had water, but then the planet changed and the water disappeared leaving behind a barren dead world.
In what could be one of the biggest findings from Mars, Nasa’s Mars Atmosphere Volatile Evolution (MAVEN) mission has detected an elusive atmospheric escape process called sputtering.
It could help answer longstanding questions about the history of water loss on Mars.
Mars is believed to have lost the water after its magnetic field disappeared exposing the planet to the solar wind and solar storms. As the atmosphere began to erode, liquid water was no longer stable on the surface, so much of it escaped to space.
Scientists are interested in finding out how its once thick atmosphere got stripped away. They think sputtering was behind it.
Sputtering, a phenomenon where energetic particles from the solar wind crash into Mars’ upper atmosphere and knock atoms into space, may have played a central role.
“It’s like doing a cannonball in a pool,” said Shannon Curry, principal investigator of MAVEN. “The heavy ions are the cannonballs, and they splash neutral atoms and molecules out of the atmosphere.”
While indirect evidence of sputtering existed — particularly in the uneven distribution of argon isotopes in the Martian atmosphere — this is the first time scientists have observed the process directly.
Using a trio of MAVEN instruments, including the Solar Wind Ion Analyzer and Neutral Gas and Ion Mass Spectrometer, the team collected rare data from both the dayside and nightside of the planet.
The result: a high-resolution map showing argon being ejected from Mars’ atmosphere precisely where solar particles collided with it. This sputtering occurred at a rate four times higher than previously thought, and intensified during solar storms.
The discovery, published this week in Science Advances, confirms sputtering as a major mechanism behind the atmospheric erosion that led to Mars’ dramatic climate shift.
“These results establish sputtering’s role in the loss of Mars’ atmosphere and in determining the history of water on Mars,” said Curry. The findings could significantly reshape our understanding of Mars’ past — and its potential to have once supported life.
