Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Keck II Observations of Hemispherical Differences in H2O2 on Europa   We present results from Keck II observations of Europa over four consecutive
nights using the near-infrared spectrograph (NIRSPEC). Spectra were collected
in the 3.14--4.0 micron range, allowing detection and monitoring of the 3.5
micron feature due to hydrogen peroxide. Galileo Near-Infrared Spectrometer
(NIMS) results first revealed hydrogen peroxide on Europa in the anti-jovian
region of the leading hemisphere at an abundance of 0.13+/-0.07% by number
abundance relative to water. We find comparable results for the two nights over
which we observed the leading hemisphere. Significantly, we observed a small
amount of hydrogen peroxide (~0.04%) during observations of Europa's anti- and
sub-Jovian hemispheres. Almost no hydrogen peroxide was detected during
observations of just the trailing hemisphere. We conclude that the Galileo
observations likely represent the maximum hydrogen peroxide concentration, the
exception potentially being the cold water ice regions of the poles, which are
not readily observable from the ground. Our mapping of the peroxide abundance
across Europa requires revisions to previous estimates for Europa's global
surface abundance of oxidants and leads to a reduction in the total oxidant
delivery expected for the sub-surface ocean, if exchange of surface material
with the ocean occurs.

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The categories of this paper are: acc-phys
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The categories of this paper are: hep-ex
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The categories of this paper are: eess
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The categories of this paper are: chao-dyn
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The categories of this paper are: dg-ga
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The categories of this paper are: hep-ph
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The categories of this paper are: quant-ph
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The categories of this paper are: gr-qc
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The categories of this paper are: nlin
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The categories of this paper are: cs
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The categories of this paper are: hep-th
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The categories of this paper are: plasm-ph
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The categories of this paper are: cond-mat
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The categories of this paper are: cmp-lg
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The categories of this paper are: atom-ph
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The categories of this paper are: math