MERCURY'S ATMOSPHERIC BRIGHT SPOTS AND POTASSIUM VARIATIONS:A POSSIBLE CAUSE



ANN L. SPRAGUE

Lunar and Planetary Laboratory
University of Arizona, Tucson, AZ 85721
sprague
fax 520-621-4933



ABSTRACT

(JGR 97, E11, 18,257-18,264, Nov.25, 1992)

An explanation is given for time-variable and spatially discrete enhancements of neutral sodium (Na) and potassium (K) in Mercury's atmosphere. Some locations of increase intensity can be explained in terms of sodium and potassium ion implantation into the surface regolith grains during the long, 88 Earth day, Mercurian night with subsequent diffusion to the atmosphere when the enriched surface of Mercury rotates into the intense sunlight of day. Support for the suggested mehcanism is shown by the K data which show a marked moring/afternoon assymmetry and can be explained by time and temperature dependent degassing. The magnetospheric mechanism necessary for ion implantation is discussed as is the diffusion mechanism. Alternative source, recycling, and distribution processes are also discussed.

Correction in JGR 98, E1, p.1231, Jan.25, 1993.