Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Impact Craters on Pluto and Charon Indicate a Deficit of Small Kuiper
  Belt Objects   The flyby of Pluto and Charon by the New Horizons spacecraft provided
high-resolution images of cratered surfaces embedded in the Kuiper belt, an
extensive region of bodies orbiting beyond Neptune. Impact craters on Pluto and
Charon were formed by collisions with other Kuiper belt objects (KBOs) with
diameters from ~40 kilometers to ~300 meters, smaller than most KBOs observed
directly by telescopes. We find a relative paucity of small craters less than
approximately 13 kilometers in diameter, which cannot be explained solely by
geological resurfacing. This implies a deficit of small KBOs (less than 1 to 2
kilometers in diameter). Some surfaces on Pluto and Charon are likely greater
than 4 billion years old, thus their crater records provide information on the
size-frequency distribution of KBOs in the early Solar System.

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The categories of this paper are: bayes-an
14
The categories of this paper are: math-ph
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The categories of this paper are: alg-geom
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The categories of this paper are: funct-an
13
The categories of this paper are: quant-ph
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The categories of this paper are: atom-ph
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The categories of this paper are: comp-gas
2
The categories of this paper are: math
30
The categories of this paper are: q-alg
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The categories of this paper are: acc-phys
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The categories of this paper are: dg-ga
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The categories of this paper are: q-fin
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The categories of this paper are: nucl-ex
0
The categories of this paper are: hep-ph
12
The categories of this paper are: nucl-th
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The categories of this paper are: gr-qc