September 28, 2004 | David F. Coppedge

Solar Wind Erodes Mars’ Atmosphere

Physics Web has a summary of a report that appeared in Science Sept. 24.1  First results from an experiment on ESA’s Mars Express called Analyzer of Space Plasma and Energetic Atoms (ASPERA-3) are in.  They show that the solar wind penetrates deep into Mars’ atmosphere, as far as 270 km above the Martian surface.  Since Mars has no global magnetic field, the energy of the solar wind strips away hydrogen and oxygen ions.  This means Mars appears to be slowly dehydrating.  Nature Science Update summarized a paper that indicates Mars once had “acid rain and briny seas.”  Surprisingly it calls this “climate ideally suited to life,” presumably because liquid water narrows the temperature.  “A warm planet is good news for the prospect that life once existed there,” it says.
    Meanwhile, back on the surface, the Mars Exploration Rovers have been given another six months of work, reports New Scientist.  Spirit and Opportunity are warming up again now that the peak of Martian winter has past.  Mars Global Surveyor took a remarkable image from orbit, showing Spirit and its tracks on the surface.


1Lundin et al., “Solar Wind-Induced Atmospheric Erosion at Mars: First Results from ASPERA-3 on Mars Express,” Science, Vol 305, Issue 5692, 1933-1936, 24 September 2004, [DOI: 10.1126/science.1101860].

Astrobiologists are filled with vibrant faith that life emerged from the bowels of hellish conditions, on Earth and on Mars both.  It was a constant theme on the PBS Origins program (see 09/13/2004 headline).  No evidence is required for this religion, just lots of maybes.  That’s why we need these spacecraft and rovers to keep patiently, silently gathering data.  Data have a way of putting dampers on wild speculations.
    The lesson from ASPERA-3 is that the solar wind is a destructive process.  It’s hard to say how long it would have taken to erode Mars’ atmosphere, because nobody was there to see how thick it was at the beginning, and when or if it had a global magnetic field.  Suffice it to say Earth would be similarly in danger if it were not for our global magnetic field protecting us.  That’s one of many factors that should make us consider the meaning of our existence on a very privileged planet.

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Categories: Physical Science, Physics

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