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Observations of sodium in the tenuous lunar atmosphere
Author(s) -
Tyler Ann L.,
Kozlowski Richard W. H.,
Hunten Donald M.
Publication year - 1988
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/gl015i010p01141
Subject(s) - regolith , planet , astrobiology , sodium , geology , atmosphere (unit) , mercury (programming language) , crust , geology of the moon , geophysics , astronomy , physics , materials science , meteorology , geochemistry , basalt , computer science , metallurgy , programming language
Spectra showing the sodium D lines above the Moon's bright limb (subsolar point) were obtained at first and last quarters, May 27 and June 7, 1988. The number density at the surface is 57 ± 20 atoms cm −3 and the scale height is 79 ± 8 km, compatible with the temperature of the surface. Comparison with the Mercurian density of 2.6×10 4 atoms cm −3 reveals an enigma. Despite the apparent general similarity of the surfaces, the sodium densities are in a ratio of ∼ 400. The difference may be attributed to differences in source or loss mechanisms or to some fundamental compositional difference between the two planets. The possibility that the source is rapid diffusion of sodium through Mercury's crust and regolith is discussed as well as recent observational evidence that Mercury's regolith is of intermediate rock type and may be more sodium‐rich than the Moon's.