Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Dune formation on the present Mars   We apply a model for sand dunes to calculate formation of dunes on Mars under
the present Martian atmospheric conditions. We find that different dune shapes
as those imaged by Mars Global Surveyor could have been formed by the action of
sand-moving winds occuring on today's Mars. Our calculations show, however,
that Martian dunes could be only formed due to the higher efficiency of Martian
winds in carrying grains into saltation. The model equations are solved to
study saltation transport under different atmospheric conditions valid for
Mars. We obtain an estimate for the wind speed and migration velocity of
barchan dunes at different places on Mars. From comparison with the shape of
bimodal sand dunes, we find an estimate for the timescale of the changes in
Martian wind regimes.

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The categories of this paper are: cmp-lg
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The categories of this paper are: dg-ga
7
The categories of this paper are: hep-th
5
The categories of this paper are: gr-qc
11
The categories of this paper are: hep-lat
14
The categories of this paper are: math-ph
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The categories of this paper are: supr-con
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The categories of this paper are: alg-geom
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The categories of this paper are: comp-gas
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The categories of this paper are: nlin
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The categories of this paper are: stat
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The categories of this paper are: chao-dyn
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The categories of this paper are: bayes-an
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The categories of this paper are: patt-sol
2
The categories of this paper are: math
17
The categories of this paper are: q-fin