P53C-2130
Quantifying Sources, Sinks and Gas-surface Interactions on the Moon from LADEE Measurements of Exospheric Na and K

Friday, 18 December 2015
Poster Hall (Moscone South)
Menelaos Sarantos, University of Maryland Baltimore County, Baltimore, MD, United States, Anthony Colaprete, NASA Ames Research Center, Moffett Field, CA, United States, Andrew R Poppe, University of California Berkeley, Berkeley, CA, United States, Christopher Bennett, Georgia Institute of Technology Main Campus, Atlanta, GA, United States and Thomas M Orlando, Georgia Inst. of Technology, Atlanta, GA, United States
Abstract:
We present numerical simulations of the generation and loss of the sodium (Na) and potassium (K) exospheres of the Moon and compare these results to recent LADEE observations. While both species appear to migrate towards the poles like other volatiles, Na resides on the soil and exosphere for one to two months before getting lost to the solar wind or the subsurface. K exhibits a different evolutionary trend: it is lost much more quickly than ionization and sputtering rates allow for, suggesting that it is lost to the ground in just a few bounces. Thus, the two alkalis exhibit very different interactions with the lunar surface. Reproducing the monthly variation exhibited by Na requires higher source rates at Mare, or higher sink rates at Highlands, or a combination of both. The very different behavior of Na on Mare and Highlands soils is reminiscent of laboratory experiments of water binding on Apollo fine soils.