Publication Date:
2018-10-16
Description:
The solar wind has been implicated as a source of water on airless bodies such as the Moon, asteroids, and possibly Mercury, yet a kinetic and mechanistic chemical model consistent with present-day observational data is still lacking. Utilizing available data sets on temperature-driven water formation and desorption from metal oxides (e.g., SiO 2 , TiO 2 , and Al 2 O 3 ) with surface hydroxyl defects (─OH) and experimental data from a lunar mare regolith Apollo sample (10084), the 2.8-μm optical signal on the Moon is modeled. Specifically, the presence and persistence of this band result from the balance of formation and loss mechanisms associated with solar wind production and thermal transformation of hydroxyls on and within the regolith. This cycle involves formation and release of molecular water via recombinative desorption of the chemically bound ─OH. Though this mechanism forms gas-phase H 2 O on the sunlit side, photodissociation and dissociative adsorption lead to rehydroxylation and very limited exospheric water over a lunation. ©2018. American Geophysical Union. All Rights Reserved.
Print ISSN:
0094-8276
Electronic ISSN:
1944-8007
Topics:
Geosciences
,
Physics
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