Spectral Properties Of Bright Deposits In Permanently Shadowed Craters On Ceres
Bright deposits in permanently shadowed craters on Ceres are thought to harbor water ice. However, the evidence for water ice presented thus far is indirect.
We aim to directly detect the spectral characteristics of water ice in bright deposits present in permanently shadowed regions (PSRs) in polar craters on Ceres.
We analyzed narrowband images of four of the largest shadowed bright deposits acquired by the Dawn Framing Camera to reconstruct their reflectance spectra, carefully considering issues such as in-field stray light correction and image compression artifacts.
The sunlit portion of a polar deposit known to harbor water ice has a negative (blue) spectral slope of −58±12 % μm−1 relative to the background in the visible wavelength range. We find that the PSR bright deposits have similarly blue spectral slopes, consistent with a water ice composition.
Based on the brightness and spectral properties, we argue that the ice is likely present as particles of high purity. Other components such as phyllosilicates may be mixed in with the ice. Salts are an unlikely brightening agent given their association with cryovolcanic processes, of which we find no trace. Our spectral analysis strengthens the case for the presence of water ice in permanently shadowed craters on Ceres.
Bright deposits in PSRs shown at the highest available resolution in FC clear filter images, with the image number indicated. Images are shown as unprojected 250×250 pixel-sized crops from the Low Altitude Mapping Orbit (LAMO; Russell et al. 2007) with the contrast enhanced in shadowed areas. — astro-ph.EP
Stefan Schröder, Norbert Schörghofer, Erwan Mazarico, Uri Carsenty
Comments: 8 pages, 8 figures
Subjects: Earth and Planetary Astrophysics (astro-ph.EP)
Cite as: arXiv:2407.15327 [astro-ph.EP] (or arXiv:2407.15327v1 [astro-ph.EP] for this version)
Related DOI:
https://doi.org/10.1051/0004-6361/202450247
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Submission history
From: Stefan Schröder
[v1] Mon, 22 Jul 2024 02:14:01 UTC (2,817 KB)
https://arxiv.org/abs/2407.15327
Astrobiology, Astrochemistry, Astrogeology,
