Clouds of
water ice drifting above the Martian surface eat up some of the ozone in Mars'
atmosphere, a new study suggests, giving scientists new clues about the
chemical environment and climate of Earth's nearest neighbor.
Mars has a
relatively stable atmosphere that is 95 percent carbon dioxide (Earth's
atmosphere is only 0.04 percent carbon dioxide).
Scientists
have had a difficult time modeling certain aspects of Mars' atmosphere and some
suspected that reactions between atmospheric gases and ice cloud particles
could account for the differences between their models and satellite
observations, particularly of ozone concentrations.
Water ice
clouds high in Earth's atmosphere are key factors in the loss of ozone above
the poles and may perturb the chemistry in layers of air below. Likewise, some
scientists thought, similar
clouds on Mars could be affecting ozone levels in Mars' atmosphere.
Franck Lefèvre
of the Universite Pierre et Marie Curie in Paris and his colleagues used new
ozone observations from the European Space Agency's Mars Express satellite,
which has been orbiting the red planet since 2003, to test the theory. Their
results are detailed in the Aug. 21 issue of the journal Nature.
They included
reactions of ozone with destructive chemicals called hydrogen radicals on the
water ice clouds, which ironed out some of the inconsistencies observed in the
models.
Hydrogen
radicals are also important to the recycling of carbon dioxide in the Martian
atmosphere, making ozone a sensitive tracer to the chemistry of the atmosphere
of Mars.
Subsurface
water ice was confirmed
to exist in the arctic regions of Mars by NASA's Phoenix Mars Lander on
July 31.
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