Leicester physicists solve disappearing Martian atmosphere mystery

Posted by mjs76 at Mar 15, 2010 03:35 PM |
It may not be breathable but Mars has an atmosphere. The trouble is: bits of it keep disappearing off into space. Now Leicester researchers have discovered why.
Leicester physicists solve disappearing Martian atmosphere mystery

Mars Express (image: ESA)

The atmosphere on Mars is 95% carbon dioxide with small amounts of nitrogen and argon plus a dribble of oxygen and methane. Not a healthy mixture if you don't have a space suit, but fascinating to our Radio and Space Plasma Physics Research Group.

Leicester physicists, working with colleagues in Sweden and Germany, have analysed Martian atmospheric escape and discovered that it is neither constant nor random but is directly affected by the solar wind. This ‘wind’ is of course not any sort of air movement but rather a stream of charged particles flowing out from the sun.

First proposed in the mid-19th century, solar wind was finally confirmed by probes such as Mariner 2 in the early 1960s which showed that it exists in two forms: slow solar wind (about 400 km/s, originating near the sun’s equator) and fast solar wind (more than 500 km/s, originating near the poles).

When slow and fast solar winds interact, they create a high-pressure pulse called a co-rotating interaction region (CIR) and it is these CIRs, the Leicester researchers have discovered, which are largely responsible for ripping away chunks of Martian atmosphere as they pass the planet. The data they used was derived from ESA’s Mars Express probe and NASA’s Advanced Composition Explorer (ACE) mission.

But don’t worry about our own atmosphere being knocked into space. Unlike Mars, Earth has a strong magnetic field which protects us from the solar wind so CIRs do not possess the same threat here.

The paper by NJT Edberg et al has been published in Geophysical Research Letters. Lead author Niklas Edberg was a Leicester doctoral student and now works at the Swedish Institute of Space Physics (IRF) in Uppsala. The other Leicester authors are Anthony Williams, Mark Lester, Steve Milan and Stan Cowley, all in our Department of Physics and Astronomy.