The Geographic Distribution Of Dense-phase O2 On Ganymede


Maps of Ganymede’s 5773 ˚A condensed O2 absorption for all of the HST/STIS visits. We observe the largest absorptions at the low- to mid-latitudes on the trailing hemisphere. We separate the observations into two pairs of visits on each panel to facilitate comparison between overlapping observations. The top panel includes the data acquired on 1999 Aug 28 (centered near 300◦W) and 1999 Sep 14 (centered near 97◦W), while the bottom panel includes data acquired on 1999 Sep 23 (centered near 193◦W) and 2020 Oct 8 (centered near 18◦W). Discrepancies between overlapping regions from these different visits are suggestive of moderate temporal variability in the dense-phase O2.

Ground-based spectroscopy of Ganymede's surface has revealed the surprising presence of dense-phase molecular oxygen (O2) via weak absorptions at visible wavelengths. To date, the state and stability of this O2 at the temperatures and pressures of Ganymede's surface are not understood.

Its spatial distribution in relation to albedo, expected temperatures, particle irradiation patterns, or composition may provide clues to these unknowns. We present spatially resolved observations of Ganymede's surface O2 obtained with the Hubble Space Telescope and construct the first comprehensive map of its geography.

In agreement with the limited spatially resolved data published previously, our map suggests that the condensed O2 is concentrated at the low- to mid-latitudes of the trailing hemisphere, a distribution that may reflect influences of Ganymede's intrinsic magnetic field on the bombardment of its surface by Jovian magnetospheric particles.

Overlapping regions from different observations within our dataset also show evidence for moderate temporal variability in the surface O2, but we are unable to distinguish between potential causes with the available data.

Samantha K. Trumbo, Michael E. Brown, Danica Adams

Comments: 7 pages, 4 figures, Accepted to the Planetary Science Journal
Subjects: Earth and Planetary Astrophysics (astro-ph.EP)
Cite as: arXiv:2106.10565 [astro-ph.EP] (or arXiv:2106.10565v1 [astro-ph.EP] for this version)
Submission history
From: Samantha Trumbo
[v1] Sat, 19 Jun 2021 19:58:34 UTC (1,587 KB)
https://arxiv.org/abs/2106.10565
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