The sunlit lunar atmosphere: A comprehensive study by CHACE on the Moon Impact Probe of Chandrayaan-1

The altitudinal/latitudinal profile of the lunar atmospheric composition on the sunlit side was unraveled for the first time by the Chandra’s Altitudinal Composition Explorer (CHACE) on the Moon Impact Probe, a standalone micro-satellite that impacted at the lunar south pole, as a part of the first Indian mission to Moon, Chandrayaan-1. Systematic measurements were carried out during the descent phase of the impactor with an altitude resolution of ∼250 m and a latitudinal resolution of ∼0.1°. The overall pressure on the dayside and the neutral composition in the mass range 1–100 amu have been measured by identifying 44 and 18 amu as the dominant constituents. Significant amounts of heavier (>50 amu) species also have been detected, the details of which are presented and discussed.