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High‐Resolution Potassium Observations of the Lunar Exosphere
Author(s) -
Rosborough S. A.,
Oliversen R. J.,
Mierkiewicz E. J.,
Sarantos M.,
Robertson S. D.,
Kuruppuaratchi D. C. P.,
Derr N. J.,
Gallant M. A.,
Roesler F. 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 - 10.1029/2019gl083022
Subject(s) - exosphere , potassium , impact crater , vaporization , line (geometry) , astrobiology , geology , physics , materials science , ion , mathematics , geometry , quantum mechanics , metallurgy , thermodynamics
Abstract We observed lunar exospheric potassium D1 (7,698.9646 Å) emissions using a high‐spectral resolution Fabry‐Perot spectrometer in 2014. We present the first potassium line profile measurements, which are representative of the potassium velocity distribution. Inferred temperatures are greater during the waxing gibbous phase, 1920±630 K and lower at waning gibbous phase, 980±200 K. Exosphere models suggest that the measured line widths are a combination of photon‐stimulated desorption and impact vaporization sources. The relative potassium emission intensity decreases by ∼2.5 between lunar phases 80° and 30° and is brightest off the northwest limb near the Aristarchus crater, which is a potassium‐rich surface region. Additionally, the emissions off the northern limb are brighter than the southern limb. The intensity decrease and the greater line width during the waxing gibbous versus the waning gibbous phase suggests a dawn‐dusk asymmetry.