On Charon's Far-ultraviolet Surface Reflectance
Abstract
We present the first measurements of Charon's far-ultraviolet (FUV) surface reflectance, obtained by the Alice spectrograph on New Horizons. We find no measurable flux shortward of 1650 Å, and Charon's geometric albedo is <0.019 (3σ) at 1600 Å. From 1650 to 1725 Å, Charon's geometric albedo increases to 0.166 ± 0.068 and remains nearly constant until 1850 Å. As this spectral shape is characteristic of H2O ice absorption, Charon is the first Kuiper Belt object with a H2O ice surface to be detected in the FUV. Charon's geometric albedo is ~3.7 times lower than Enceladus's at these wavelengths but has a very similar spectral shape. We attribute this to similarities in their surface compositions and the difference in absolute reflectivity to a high concentration or more-absorbing contaminants on Charon's surface. Finally, we find that Charon has different solar phase behavior in the FUV than Enceladus, Mimas, Tethys, and Dione, with a stronger opposition surge than Enceladus and a shallower decline at intermediate solar phase angles than any of these Saturnian satellites.
- Publication:
-
The Planetary Science Journal
- Pub Date:
- August 2021
- DOI:
- 10.3847/PSJ/ac16da
- arXiv:
- arXiv:2107.14068
- Bibcode:
- 2021PSJ.....2..164K
- Keywords:
-
- Plutonian satellites;
- Ultraviolet photometry;
- 2202;
- 1740;
- Astrophysics - Earth and Planetary Astrophysics
- E-Print:
- Accepted for publication in the Planetary Science Journal