Martian Balding: Mars Lost its Full Head of Atmosphere Some 4 Billion Years Ago

In what can only be described as a case of planetary balding, new research indicates that Mars once had a thick, lush atmosphere at one point in time that slowly thinned over the past four billion years.

Mars, it turns out, had an atmosphere thicker than Earth's at one time, but cataclysmic events some 3-4 billion years ago changed all that. The findings are detailed in two separate studies published in the journal Science.

"Getting the same result with two very different techniques increased our confidence that there's no unknown systematic error underlying the measurements," said Chris Webster from NASA's Jet Propulsion Laboratory, Pasadena, Calif. "The accuracy in these new measurements improves the basis for understanding the atmosphere's history."

The studies were carried out with data collected by NASA's Mars Curiosity Rover, which has been slowly stockpiling evidence that the Red Planet was once home to liquid water - the philosopher's stone for biological life as we know it. The researchers compared the ratio of heavy isotopes of carbon and argon to their lighter counterparts. By observing how these may have changed over time, the scientists were able to deduce that Mars once had a thick atmosphere, and that it began to decline while the planet was still an infant.

"It is a good bet that the thicker atmosphere could have kept parts of the planet warm enough for microbial life to survive for a while," said Paul Mahaffy from NASA's Goddard Space Flight Center

However, Mahaffy added, "A big question that still needs an answer is how long the surface of the planet might have stayed warm and was this long enough for robust microbial life to develop and thrive,"

According to the research, the thinning of the Martian atmosphere was the result of giant meteoric impacts that not only created giant rips in the atmosphere, but affected the planet's magnetic orientation, causing more harmful particles to slowly wear down the protective outer layer. The studies also state that atmospheric loss may still be ongoing.   

You can read both the published studies in the journal Science here and here.