An artist's illustration of the MAVEN spacecraft and the limb of Mars. Credit: NASA's Goddard Space Flight Center
The Martian atmosphere was stripped away by the destructive power of the Sun, according to new data from NASA's MAVEN (Mars Atmosphere and Volatile Evolution Mission) spacecraft.
The data has revealed that about 65 per cent of the argon in Mars’s atmosphere was lost to space in this way.
While today Mars is a barren landscape, evidence exists that it once had an atmosphere, and that liquid water flowed on its surface during its early history.
Evidence for this is seen in formations in the surface of the Red Planet such as dried river beds and channels possibly carved by running water.
Once a planet that could have hosted life, the Martian atmosphere was lost by strong radiation and solar winds, which are streams of charged particles given off by the Sun.
The early Sun had much more intense ultraviolet radiation and solar winds, and this was responsible for the transformation of the Red Planet’s climate.
As a result, any microbial life that once existed could have been driven underground in order to survive.
The loss of argon is particularly telling as it does not react with anything, so could not have been hidden in Martian rocks.
Therefore, it must have been ejected from the planet by ions picked up by the solar winds hitting Mars at high speeds and knocking atmospheric gas into space.
This process is known as ‘sputtering’.
"We determined that the majority of the planet's CO2 also has been lost to space by sputtering," says Bruce Jakosky, principal investigator for MAVEN.
"There are other processes that can remove CO2, so this gives the minimum amount of CO2 that's been lost to space."