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The Young Age of the LAMP‐observed Frost in Lunar Polar Cold Traps
Author(s) -
Farrell W. M.,
Hurley D. M.,
Poston M. J.,
Hayne P. O.,
Szalay J. R.,
McLain J. L.
Publication year - 2019
Publication title -
geophysical research letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.007
H-Index - 273
eISSN - 1944-8007
pISSN - 0094-8276
DOI - 10.1029/2019gl083158
Subject(s) - impact crater , orbiter , regolith , astrobiology , exosphere , geology , lunar craters , polar , astronomy , physics , ion , quantum mechanics
The Lunar Reconnaissance Orbiter/Lyman Alpha Mapping Project (LAMP) ultraviolet instrument detected a 0.5–2% icy regolith mix on the floor of some of the southern pole permanently shadowed craters of the Moon. We present calculations indicating that most or all of this icy regolith detected by LAMP (sensed to a depth of <1 μm) has to be relatively young—less than 2,000 years old—due to the surface erosional loss by plasma sputtering (external ionized gas‐surface interactions), meteoric impact vaporization, and meteoric impact ejection. These processes, especially meteoric impact ejection, will disperse water along the crater floor, even onto warm regions where it will then undergo desorption. We have determined that there should be a water exosphere over polar craters (e.g., like Haworth crater) and calculated that a model 40‐km‐diameter crater should emit ~10 19 H 2 O per second into the exosphere in the form of free molecules and ice‐embedded particulates.