Solar Wind Stripping the Martian Atmosphere

We know that Mars lost an ocean of water, but what was the exact mechanism?  We also know that the magnetic field of Mars was lost a long time ago, and contributed to this major loss of water and atmosphere.  In a press conference today, NASA officials working with data from the Mars Atmosphere and Volatile Evolution (MAVEN) spacecraft, have shown that major solar storms have increased the amount of atmosphere and water loss over time.

Artist’s rendering of a solar storm hitting Mars and stripping ions from the planet’s upper atmosphere. Credits: NASA/GSFC

“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.”

Data from MAVEN has shown that about 100 grams of gas is stripped away by the solar wind each second.  That adds up significantly over billions of years.  The gas is stripped away by the solar wind in three distinct regions, a ‘polar plume,’ a ‘tail’ behind Mars, and an extended cloud of gas surrounding Mars.  The video below shows a NASA visualization of the regions as solar wind particles collide with the planet.

The new findings put a more specific mechanism on a piece of science we were aware of, that a once rich supply atmosphere and water were lost to the emptiness of space.

“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.”

We are starting to understand the past and present of our enigmatic neighbour.

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