Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Evidence of sub-surface energy storage in comet 67P from the outburst of
  2016 July 3   On 3 July 2016, several instruments on board ESA's Rosetta spacecraft
detected signs of an outburst event on comet 67P, at a heliocentric distance of
3.32 AU from the sun, outbound from perihelion. We here report on the inferred
properties of the ejected dust and the surface change at the site of the
outburst. The activity coincided with the local sunrise and continued over a
time interval of 14 - 68 minutes. It left a 10m-sized icy patch on the surface.
The ejected material comprised refractory grains of several hundred microns in
size, and sub-micron-sized water ice grains. The high dust mass production rate
is incompatible with the free sublimation of crystalline water ice under solar
illumination as the only acceleration process. Additional energy stored near
the surface must have increased the gas density. We suggest a pressurized
sub-surface gas reservoir, or the crystallization of amorphous water ice as
possible causes.

22
The categories of this paper are: chao-dyn
15
The categories of this paper are: nucl-ex
31
The categories of this paper are: ao-sci
14
The categories of this paper are: math-ph
35
The categories of this paper are: mtrl-th
16
The categories of this paper are: stat
32
The categories of this paper are: atom-ph
20
The categories of this paper are: acc-phys
17
The categories of this paper are: q-fin
7
The categories of this paper are: hep-th
19
The categories of this paper are: eess
4
The categories of this paper are: cond-mat
11
The categories of this paper are: hep-lat
3
The categories of this paper are: physics
34
The categories of this paper are: chem-ph
18
The categories of this paper are: econ