Hydrogen Mapping of the Lunar South Pole Using the LRO Neutron Detector Experiment LEND

I. G. Mitrofanov1, A. B. Sanin1, W. V. Boynton2, G. Chin3, J. B. Garvin3, D. Golovin1, L. G. Evans4, K. Harshman2, A. S. Kozyrev1, M. L. Litvak1, A. Malakhov1, E. Mazarico3, T. McClanahan3, G. Milikh5, M. Mokrousov1, G. Nandikotkur5, G. A. Neumann3, I. Nuzhdin1, R. Sagdeev5, V. Shevchenko7, V. Shvetsov8, D. E. Smith9, R. Starr6, V. I. Tretyakov1, J. Trombka10, D. Usikov5, A. Varenikov1, A. Vostrukhin1 and M. T. Zuber9

1Institute for Space Research of the Russian Academy of Science, 117997 Moscow, Russia.
2University of Arizona, Tucson, AZ, USA.
3NASA Goddard Space Flight Center, Greenbelt, MD, USA.
4Computer Science Corporation, Greenbelt, MD, USA.
5Department of Physics, University of Maryland, College Park, MD, USA.
6Catholic University, Washington, DC, USA.
7Sternberg Astronomical Institute of Moscow State University, Moscow, Russia.
8Joint Institute of Nuclear Research, Dubna, Russia.
9Massachusetts Institute of Technology, Cambridge, MA, USA.
10Department of Astronomy, University of Maryland, College Park, MD, USA.

Abstract - Hydrogen has been inferred to occur in enhanced concentrations within permanently shadowed regions and, hence, the coldest areas of the lunar poles. The Lunar Crater Observation and Sensing Satellite (LCROSS) mission was designed to detect hydrogen-bearing volatiles directly. Neutron flux measurements of the Moon's south polar region from the Lunar Exploration Neutron Detector (LEND) on the Lunar Reconnaissance Orbiter (LRO) spacecraft were used to select the optimal impact site for LCROSS. LEND data show several regions where the epithermal neutron flux from the surface is suppressed, which is indicative of enhanced hydrogen content. These regions are not spatially coincident with permanently shadowed regions of the Moon. The LCROSS impact site inside the Cabeus crater demonstrates the highest hydrogen concentration in the lunar south polar region, corresponding to an estimated content of 0.5 to 4.0% water ice by weight, depending on the thickness of any overlying dry regolith layer. The distribution of hydrogen across the region is consistent with buried water ice from cometary impacts, hydrogen implantation from the solar wind, and/or other as yet unknown sources.
DOI: 10.1126/science.1185696 - http://www.sciencemag.org/content/330/6003/483.abstract