P43F-05
Possible Albedo Proton Signature of Hydrated Lunar Surface Layer
Thursday, 17 December 2015: 14:40
2007 (Moscone West)
Nathan Schwadron1, Jody Keith Wilson1, Mark Dixon Looper2, Andrew Jordan1, Harlan E. Spence1, J Bernard Blake3, Anthony W Case4, Yoshi Iwata5, Justin Christophe Kasper6, William M Farrell7, David J Lawrence8, George Livadiotis9, Joseph E Mazur10, Noah E Petro11, Carle M Pieters12, Mark Southwick Robinson13, Sonya S Smith14, Lawrence W Townsend15, Cary J Zeitlin16 and LRO/CRaTER team, (1)University of New Hampshire Main Campus, Space Science Center, Durham, NH, United States, (2)Aerospace Corporation El Segundo, El Segundo, CA, United States, (3)Aerospace Corporation Santa Monica, Santa Monica, CA, United States, (4)Smithsonian Astrophysical Observatory, Cambridge, MA, United States, (5)NIRS National Institute of Radiological Sciences, Chiba, Japan, (6)University of Michigan Ann Arbor, Ann Arbor, MI, United States, (7)NASA Goddard SFC, Greenbelt, MD, United States, (8)Johns Hopkins University, Baltimore, MD, United States, (9)Southwest Research Institute, San Antonio, TX, United States, (10)Aerospace Corporation Chantilly, Chantilly, VA, United States, (11)NASA GSFC, Greenbelt, MD, United States, (12)Brown University, Earth, Environmental and Planetary Sciences, Providence, RI, United States, (13)Arizona State University, School of Earth and Space Exploration, Tempe, AZ, United States, (14)University of New Hampshire Main Campus, Durham, NH, United States, (15)University of Tennessee, Knoxville, TN, United States, (16)Southwest Research Institute Boulder, Earth, Oceans & Space Department, Boulder, CO, United States
Abstract:
We find evidence for a surface layer of hydrated material in the lunar regolith using “albedo protons” measured by the Cosmic Ray Telescope for the Effects of Radiation (CRaTER) on the Lunar Reconnaissance Orbiter (LRO). Fluxes of these albedo protons, which are emitted from the regolith due to steady bombardment by high-energy radiation (Galactic Cosmic Rays), are observed to peak near the poles, and cannot be accounted for by either heavy element enrichment (e.g., enhanced Fe abundance), or by deeply buried (> 50 cm) hydrogenous material. The latitudinal distribution of albedo protons does not correlate with that of epithermal or high-energy neutrons. The high latitude enhancement may be due to the conversion of upward directed secondary neutrons from the lunar regolith into tertiary protons due to neutron-proton collisions in a thin (~ 1-10 cm) layer of hydrated regolith near the surface that is more prevalent near the poles. The CRaTER instrument thus provides critical measurements of volatile distributions within lunar regolith and potentially, with similar sensors and observations, at other bodies within the Solar System.
