Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Evidence for explosive silicic volcanism on the Moon from the extended
  distribution of thorium near the Compton-Belkovich Volcanic Complex   We reconstruct the abundance of thorium near the Compton-Belkovich Volcanic
Complex on the Moon, using data from the Lunar Prospector Gamma Ray
Spectrometer. We enhance the resolution via a pixon image reconstruction
technique, and find that the thorium is distributed over a larger ($40
\mathrm{km}\times 75$ km) area than the ($25 \mathrm{km}\times 35$ km) high
albedo region normally associated with Compton-Belkovich. Our reconstructions
show that inside this region, the thorium concentration is $14\!-\!26$ ppm. We
also find additional thorium, spread up to $300$ km eastward of the complex at
$\sim\!2$ ppm. The thorium must have been deposited during the formation of the
volcanic complex, because subsequent lateral transport mechanisms, such as
small impacts, are unable to move sufficient material. The morphology of the
feature is consistent with pyroclastic dispersal and we conclude that the
present distribution of thorium was likely created by the explosive eruption of
silicic magma.

20
The categories of this paper are: acc-phys
5
The categories of this paper are: gr-qc
33
The categories of this paper are: plasm-ph
25
The categories of this paper are: patt-sol
4
The categories of this paper are: cond-mat
2
The categories of this paper are: math
3
The categories of this paper are: physics
34
The categories of this paper are: chem-ph
13
The categories of this paper are: quant-ph
14
The categories of this paper are: math-ph
9
The categories of this paper are: nlin
37
The categories of this paper are: supr-con
29
The categories of this paper are: funct-an
35
The categories of this paper are: mtrl-th
22
The categories of this paper are: chao-dyn
19
The categories of this paper are: eess