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Science 7 September 1990:
Vol. 249. no. 4973, pp. 1140 - 1143
DOI: 10.1126/science.249.4973.1140
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Articles

Caloris Basin: An Enhanced Source for Potassium in Mercury's Atmosphere

Ann L. Sprague 1, Richard W. H. Kozlowski 1, and Donald M. Hunten 1

1 Department of Planetary Sciences, University of Arizona, Tucson, AZ 85721

Enhanced abundances of neutral potassium (K) in the atmosphere of Mercury have been found above the longitude range containing Caloris Basin. Results of a large data set including six elongations of the planet between June 1986 and January 1988 show typical K column abundances of sim5.4 x 108 K atoms/cm2. During the observing period in October 1987, when Caloris Basin was in view, the typical K column was sim2.7 x 109 K atoms/cm2. Another large value (2.1 x 109 K atoms/cm2) was seen over the Caloris antipode in January 1988. This enhancement is consistent with an increased source of K from the well-fractured crust and regolith associated with this large impact basin. The phenomenon is localized because at most solar angles, thermal alkali atoms cannot move more than a few hundred kilometers from their source before being lost to ionization by solar ultraviolet radiation.


THIS ARTICLE HAS BEEN CITED BY OTHER ARTICLES:
Evidence for a basalt-free surface on Mercury and implications for internal heat.
R Jeanloz, D. Mitchell, A. Sprague, and I de Pater (1995)
Science 268, 1455-1457
   Abstract »    PDF »
Mercury Radar Imaging: Evidence for Polar Ice.
M. A. Slade, M. A. Slade, B. J. Butler, and D. O. Muhleman (1992)
Science 258, 635-640
   Abstract »    PDF »
Detecting Potassium on Mercury.
R. M. Killen, R. M. KILLEN, A. E. POTTER, and T. H. MORGAN (1991)
Science 252, 974-975
   PDF »
Response.
A. L. SPRAGUE, R. W. H. KOZLOWSKI, and D. M. HUNTEN (1991)
Science 252, 975
   PDF »


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Science. ISSN 0036-8075 (print), 1095-9203 (online)