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Investigation of Water Interactions With Apollo Lunar Regolith Grains
Author(s) -
Jones Brant M.,
Aleksandrov Aleksandr,
Dyar M. Darby,
Hibbitts Charles A.,
Orlando Thomas M.
Publication year - 2020
Publication title -
journal of geophysical research: planets
Language(s) - English
Resource type - Journals
eISSN - 2169-9100
pISSN - 2169-9097
DOI - 10.1029/2019je006147
Subject(s) - desorption , regolith , astrobiology , analytical chemistry (journal) , materials science , adsorption , chemistry , physics , environmental chemistry
Desorption activation energies of chemisorbed water on Apollo lunar Samples 14163 and 10084 were determined by temperature program desorption (TPD) experiments conducted under ultrahigh vacuum conditions. Desorption at the grain/vacuum interface and desorption/transport of water though the porous medium with readsorption were found to reproduce the experimental TPD signal. Signal from the grain/vacuum interface yielded desorption activation energies and site probability distributions. Highland sample 14163 exhibited a broad distribution of binding site energies peaking at 60 kJ mol −1 , while mare sample 10084 exhibited a narrower distribution of binding site energies peaking at 65 kJ mol −1 . The highland sample adsorbed approximately 30% more water than the more space weathered and mature mare sample, suggesting maturity may not be a good predictor of the degree of molecular water uptake on lunar regolith. Water desorption from the lunar surface over a typical lunar day was simulated with the measured coverage‐dependent activation energies of the mare and highland samples. The resulting desorption profile of water through a lunar temperature cycle is in general agreement with Lunar Reconnaissance Orbiter (LRO) Lyman‐α Mapping Project (LAMP) spacecraft‐based observations of trends for both highland and mare assuming ~1% submonolayer coverage and that photon stimulated desorption is neglected.