LADEE NMS Observations of Sporadic Water and Carbon Dioxide Signatures in the Lunar Exosphere

Tuesday, 16 December 2014: 8:15 AM
Mehdi Benna, NASA - GSFC, Greenbelt, MD, United States, Paul R Mahaffy, NASA Goddard SFC, Greenbelt, MD, United States, Dana Hurley, Applied Physics Laboratory Johns Hopkins, Laurel, MD, United States, Timothy John Stubbs, NASA Goddard Space Flight Center, Greenbelt, MD, United States, R Richard Hodges Jr, Univ of Colorado--LASP, Frisco, CO, United States and Richard C Elphic, NASA Ames Research Center, Moffett Field, CA, United States
During its six months in orbit, the Lunar Atmosphere and Dust Environment Explorer (LADEE) has detected signatures of water and carbon dioxide in the exosphere of the Moon. The signature of these two volatile gases has been measured by the Neutral Mass Spectrometer (NMS) as sporadic short-lived signal increases above instrument background. Following the detection of these two species in the exosphere, a systematic measurement campaign with a cadence of few hours over four main lunar local time sectors (sunrise, midnight, sunset, and noon) was put in place and continued to the end of the mission. While this measurement campaign did not reveal any local time dependence for these sporadic signal events, it showed that they are globally correlated with predicted micrometeoroid streams. Moreover, a subset of these NMS observations were acquired at low altitudes when water and carbon dioxide signals were below instrumental background, and used to establish new upper limits of the background abundances of these two gases in the exosphere.