Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Mars Before the Space Age   Mars has surely been scrutinised since the dawn of humankind. In the 16th
century Tycho Brahe made accurate observations of the position of Mars that
enabled Johannes Kepler to obtain his first two laws of planetary motion. In
the 17th century the first telescope observations were made, but very little
surface detail could be discerned. Throughout the 18th and 19th centuries
telescopes improved, revealing many dark areas on the red tinted surface. After
the close opposition of 1877 Giovanni Schiaparelli announced about 40 canali on
Mars. This led to the saga of the canals of Mars, laid to rest in 1971 when
Mariner 9 made observations from Martian orbit showing that the canali/canals
of Mars do not exist. Belief that there was life on Mars was widespread in the
19th century, including the view that the dark areas were some form of plant
life. This view persisted until Mariner 4 flew past Mars in 1965 and discovered
a far thinner atmosphere than previously thought, with impact craters
dominating the images. It was Mariner 9 that revealed much more promising
landscapes. Thus, the contemporary era of Mars exploration began. Our picture
of Mars today is not only much more complete that that before Mariner 4, in
several ways it is quite different. The belief however, that there may be life
on Mars persists - subsurface life cannot be ruled out and, failing that, there
might be ancient fossils on Mars.

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The categories of this paper are: hep-lat
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The categories of this paper are: q-alg
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The categories of this paper are: dg-ga
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The categories of this paper are: patt-sol
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The categories of this paper are: comp-gas
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The categories of this paper are: funct-an
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The categories of this paper are: cmp-lg
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The categories of this paper are: supr-con
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The categories of this paper are: bayes-an
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The categories of this paper are: nlin
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The categories of this paper are: hep-ex
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The categories of this paper are: quant-ph
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The categories of this paper are: eess
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The categories of this paper are: q-bio
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The categories of this paper are: q-fin
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The categories of this paper are: hep-th