Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Asymmetric impacts of near-Earth asteroids on the Moon   Recent lunar crater studies have revealed an asymmetric distribution of rayed
craters on the lunar surface. The asymmetry is related to the synchronous
rotation of the Moon: there is a higher density of rayed craters on the leading
hemisphere compared with the trailing hemisphere. Rayed craters represent
generally the youngest impacts. The purpose of this paper is to test the
hypotheses that (i) the population of Near-Earth asteroids (NEAs) is the source
of the impactors that have made the rayed craters, and (ii) that impacts by
this projectile population account quantitatively for the observed asymmetry.
We carried out numerical simulations of the orbital evolution of a large number
of test particles representing NEAs in order to determine directly their impact
flux on the Moon. The simulations were done in two stages. In the first stage
we obtained encounter statistics of NEAs on the Earth's activity sphere. In the
second stage we calculated the direct impact flux of the encountering particles
on the surface of the Moon; the latter calculations were confined within the
activity sphere of the Earth. A steady-state synthetic population of NEAs was
generated from a debiased orbital distribution of the known NEAs. We find that
the near-Earth asteroids do have an asymmetry in their impact flux on the Moon:
apex-to-antapex ratio of 1.32 +/- 0.01. However, the observed rayed crater
distribution's asymmetry is significantly more pronounced: apex-to-antapex
ratio of 1.65 +/- 0.16. Our results suggest the existence of an undetected
population of slower (low impact velocity) projectiles, such as a population of
objects nearly coorbiting with Earth; more observational study of young lunar
craters is needed to secure this conclusion.

20
The categories of this paper are: acc-phys
37
The categories of this paper are: supr-con
12
The categories of this paper are: nucl-th
32
The categories of this paper are: atom-ph
11
The categories of this paper are: hep-lat
35
The categories of this paper are: mtrl-th
16
The categories of this paper are: stat
36
The categories of this paper are: cmp-lg
2
The categories of this paper are: math
25
The categories of this paper are: patt-sol
17
The categories of this paper are: q-fin
10
The categories of this paper are: q-bio
13
The categories of this paper are: quant-ph
15
The categories of this paper are: nucl-ex
1
The categories of this paper are: cs
22
The categories of this paper are: chao-dyn