P51D-07
How LEND sees the water on the Moon: the recent findings

Friday, 18 December 2015: 09:30
2007 (Moscone West)
Anton B. Sanin1, Igor G. Mitrofanov1, Maxim L Litvak1, Boris N Bakhtin1, Julia Bodnarik2, William V Boynton3, Gordon Chin4, Larry G. Evans5, Dmitry Golovin1, Karl Harshman2, Timothy A Livengood6, Alexey V Malakhov1, Timothy P McClanahan7, Maxim Mokrousov1, Roald Sagdeev8, Richard D Starr9 and Andrey Vostrukhin1, (1)Space Research Institute RAS, Moscow, Russia, (2)Univ Arizona, Tucson, AZ, United States, (3)University of Arizona, Tucson, AZ, United States, (4)NASA Goddard Space Flight Center, Code 693, Greenbelt, MD, United States, (5)Computer Sciences Corporation, Stennis Space Center, MS, United States, (6)NASA Goddard SFC, Greenbelt, MD, United States, (7)NASA Goddard Space Flight Center, Code 691, Greenbelt, MD, United States, (8)University of Maryland College Park, Physics, College Park, MD, United States, (9)Catholic University of America, Washington, DC, United States
Abstract:
The Lunar Exploration Neutron Detector (LEND) is operating on orbit around the Moon on-board the Lunar Reconnaissance Orbiter (LRO) spacecraft about six years. LEND has been designed and manufactured to investigate presence and determine average amount of hydrogen in upper (~1 m depth) subsurface layer of the Lunar regolith with spatial resolution ~10 km from 50 km orbit and to check the hypothesis what the permanently shadowed regions (PSRs) at circumpolar regions are the main reservoirs of a large deposition of water ice on the Moon.

One of most interesting and surprising LEND observations that not all large PSRs regions contain a detectable amount of hydrogen but there are neutron suppression regions (NSRs) with statistically significant suppression of neutron flux. The NSRs partially overlap or include PSRs in Cabeus, Shoemaker, Haworth (on South) and Rozhdestvensky U (on North) but significant part of their area spread out at sunlit territory. This means that hydrogen may be preserved for a long time or even accumulated at ~1 m layer of regolith illuminated by Sun. The majority of PSRs do not show statistically significant suppressions of neutron flux in comparison with neighbor sunlit areas. This implies a hypothesis what a permanent shadow is not only necessary condition for the hydrogen hydrogen accumulation and preservation in the lunar subsurface. It is supported by analysis of poleward-facing and equatorial-facing slopes of craters. This analysis shows a statistically significant increasing of hydrogen concentration at poleward-facing slopes in comparison to equatorial-facing slopes. Moreover, it was found evidence that hydrogen-bearing volatiles are being diurnally cycled at the top meter of the Moon’s high-latitude surfaces, above ±75°.

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