Michael Meyer, the lead scientist for the Mars Exploration Program, summed up how Mars lost its atmosphere with a Bob Dylan quote: “The answer, my friend, is blowin’ in the wind.”
Via NASA’s Mars Atmosphere and Volatile Evolution (MAVEN) mission, NASA scientists have discovered the Martian atmosphere is losing gas at a rate of 100 g/sec due to stripping solar winds.
Ancient Mars was quite different than the cold, dry and desert-like planet it is today. It had a thick atmosphere warm enough to support liquid water, which scientists believe may have been the home to microbial life. Valleys on the surface appear to have been formed by rivers, and scientists believe the planet was once home to lakes and possibly oceans.
Today, the atmosphere is thin; the surface, unsuitable for sustaining liquid water extensively.
“Understanding what happened to the Mars atmosphere will inform our knowledge of the dynamics and evolution of any planetary atmosphere,” said John Grunsfeld, NASA Science Mission Directorate’s associate administrator. “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.”
MAVEN has been orbiting Mars since Sept. 2014. The recent results come from six months-worth of data. “MAVEN is designed to understand the changes of climate,” said Bruce Jakosky, the mission’s principal investigator.
Made up mainly of protons and electrons, solar wind travels from the sun’s atmosphere at speeds around 1 million mph. “New results indicate that the loss is experienced in three different regions of the Red Planet: down the ‘tail,’ where the solar wind flows behind Mars, above the Martian poles in a ‘polar plume,’ and from an extended cloud of gas surrounding Mars,” according to NASA.
According to Dave Brain, a MAVEN co-investigator, 75% of the atmosphere’s escaping ions do so via the tail region, and 25% via the plume. “I can’t help but imagine hamburgers flying out of the atmosphere at every second,” joked Brain, referencing the 100 g/sec loss, which is equivalent to a quarter pound.
Unlike Mars, the Earth is outfitted with a strong magnetic global field which helps shield it from detrimental effects of solar wind. However, the planet still loses some particles.
According to Jakosky, the current solar wind stripping activity on Mars is enough to deplete an atmosphere over billions of years. The process must have been much greater in the past, he said.
“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,” said Joe Gebowsky, a MAVEN project scientist.
MAVEN will complete its year-long primary mission on Nov. 16, then embark on an extended mission.