Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Melting and Mixing States of the Earth's Mantle after the Moon-Forming
  Impact   The Earth's Moon is thought to have formed by an impact between the Earth and
an impactor around 4.5 billion years ago. This impact could have been so
energetic that it could have mixed and homogenized the Earth's mantle. However,
this view appears to be inconsistent with geochemical studies that suggest that
the Earth's mantle was not mixed by the impact. Another plausible outcome is
that this energetic impact melted the whole mantle, but the extent of mantle
melting is not well understood even though it must have had a significant
effect on the subsequent evolution of the Earth's interior and atmosphere. To
understand the initial state of the Earth's mantle, we perform giant impact
simulations using smoothed particle hydrodynamics (SPH) for three different
models: (a) standard: a Mars-sized impactor hits the proto-Earth, (b)
fast-spinning Earth: a small impactor hits a rapidly rotating proto-Earth, and
(c) sub-Earths: two half Earth-sized planets collide. We use two types of
equations of state (MgSiO3 liquid and forsterite) to describe the Earth's
mantle. We find that the mantle remains unmixed in (a), but it may be mixed in
(b) and (c). The extent of mixing is most extensive in (c). Therefore, (a) is
most consistent and (c) may be least consistent with the preservation of the
mantle heterogeneity, while (b) may fall between. We determine that the Earth's
mantle becomes mostly molten by the impact in all of the models. The choice of
the equations of state does not affect these outcomes. Additionally, our
results indicate that entropy gains of the mantle materials by a giant impact
cannot be predicted well by the Rankine-Hugoniot equations. Moreover, we show
that the mantle can remain unmixed on a Moon-forming timescale if it does not
become mixed by the impact.

28
The categories of this paper are: alg-geom
11
The categories of this paper are: hep-lat
15
The categories of this paper are: nucl-ex
33
The categories of this paper are: plasm-ph
31
The categories of this paper are: ao-sci
1
The categories of this paper are: cs
24
The categories of this paper are: dg-ga
34
The categories of this paper are: chem-ph
25
The categories of this paper are: patt-sol
19
The categories of this paper are: eess
21
The categories of this paper are: adap-org
0
The categories of this paper are: hep-ph
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The categories of this paper are: mtrl-th
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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