Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Spitzer Evidence for a Late Heavy Bombardment and the Formation of
  Urelites in {\eta} Corvi at ~1 Gyr   We have analyzed Spitzer and NASA/IRTF 2 - 35 \mum spectra of the warm, ~350
K circumstellar dust around the nearby MS star {\eta} Corvi (F2V, 1.4 \pm 0.3
Gyr). The spectra show clear evidence for warm, water- and carbon-rich dust at
~3 AU from the central star, in the system's Terrestrial Habitability Zone.
Spectral features due to ultra-primitive cometary material were found, in
addition to features due to impact produced silica and high temperature
carbonaceous phases. At least 9 x 10^18 kg of 0.1 - 100 \mum warm dust is
present in a collisional equilibrium distribution with dn/da ~ a^-3.5, the
equivalent of a 130 km radius KBO of 1.0 g/cm^3 density and similar to recent
estimates of the mass delivered to the Earth at 0.6 - 0.8 Gyr during the Late
Heavy Bombardment. We conclude that the parent body was a Kuiper-Belt body or
bodies which captured a large amount of early primitive material in the first
Myrs of the system's lifetime and preserved it in deep freeze at ~150 AU. At
~1.4 Gyr they were prompted by dynamical stirring of their parent Kuiper Belt
into spiraling into the inner system, eventually colliding at 5-10 km/sec with
a rocky planetary body of mass \leq MEarth at ~3 AU, delivering large amounts
of water (>0.1% of MEarth's Oceans) and carbon-rich material. The Spitzer
spectrum also closely matches spectra reported for the Ureilite meteorites of
the Sudan Almahata Sitta fall in 2008, suggesting that one of the Ureilite
parent bodies was a KBO.

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The categories of this paper are: bayes-an
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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: math
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The categories of this paper are: hep-ex
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The categories of this paper are: patt-sol
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The categories of this paper are: gr-qc
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The categories of this paper are: quant-ph
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The categories of this paper are: cs
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The categories of this paper are: chao-dyn
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The categories of this paper are: hep-ph
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The categories of this paper are: q-alg
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The categories of this paper are: funct-an
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The categories of this paper are: stat
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The categories of this paper are: adap-org
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The categories of this paper are: plasm-ph