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Air Leaks from Mars
Like a comet, Mars has a tail, a stream of particles pushed away from the planet by the Sun's energy.
New measurements of the Martian tail reveal how much air the planet loses to space every day and allow scientists to estimate the tremendous loss that may have occurred billions of years ago, making the red planet the dry and cold world it is.
Theory holds that Mars once had a thick atmosphere, but today it is about 1 percent as dense as the air on Earth. Nobody is sure exactly where it all went, but a planetary tail, kicked up by a solar wind, is one likely culprit.
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