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Evolution Of Granular Salty Ice Analogs For Europa: Sublimation And Irradiation

By Keith Cowing
Status Report
astro-ph.EP
May 20, 2025
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Evolution Of Granular Salty Ice Analogs For Europa: Sublimation And Irradiation
A sample of SPIPA-B ice with 3wt% NaCl before (left) and after (right) sublimation at high temperatures (>195 K) for 24h imaged in the simulation chamber with a long-distance microscope. Before inserting it into the chamber, the ice was warmed up under the N2 atmosphere, and therefore, the particles formed clumps. These clumps do not disintegrate during sublimation and individual particles stay in place. — astro-ph.EP

We study the evolution of the Vis-NIR reflectance spectrum of salty granular ice analog samples in a simulation chamber under conditions relevant to the surface of Europa.

A novel application and custom calibration of a thermopile sensor enabled the measurement of the surface temperature of the samples in far infrared emission. This allows the kinetics of the observed changes to be scaled to equivalent timescales on Europa.

We observed significant changes in the depth and shape of the broad water absorption bands for all samples on timescales of a few thousand years of equatorial conditions on Europa. This effect should be taken into account if quantitative predictions about bulk composition are made based on remote-sensing data. A narrow absorption feature attributed to hydrohalite formed during the sublimation of the sodium chloride sample.

We used near-infrared spectroscopy in an irradiation chamber to assess the stability of this narrow feature under electron irradiation. We find that the radiation environment present on Europa dehydrates the hydrohalite on short timescales.

Therefore, we expect hydrohalite not to be present on the surface, unless erupted very recently (< 10 yr) or located in thermal anomalies (> 145 K). Thus, a detection of hydrohalite would clearly indicate recent activity.

Rafael Ottersberg, Antoine Pommerol, Linus Leo Stöckli, Lorenzo Obersnel, André Galli, Axel Murk, Peter Wurz, Nicolas Thomas

Comments: 13 pages, 9 figures, accepted for publication in Icarus
Subjects: Earth and Planetary Astrophysics (astro-ph.EP); Instrumentation and Methods for Astrophysics (astro-ph.IM)
Cite as: arXiv:2505.11498 [astro-ph.EP] (or arXiv:2505.11498v1 [astro-ph.EP] for this version)
https://doi.org/10.48550/arXiv.2505.11498
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Related DOI:
https://doi.org/10.1016/j.icarus.2025.116590
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Submission history
From: Rafael Ottersberg
[v1] Fri, 16 May 2025 17:59:54 UTC (3,622 KB)
https://arxiv.org/abs/2505.11498
Astrobiology,

Keith Cowing

Explorers Club Fellow, ex-NASA Space Station Payload manager/space biologist, Away Teams, Journalist, Lapsed climber, Synaesthete, Na’Vi-Jedi-Freman-Buddhist-mix, ASL, Devon Island and Everest Base Camp veteran, (he/him) 🖖🏻

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