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Science 1 May 2009:
Vol. 324. no. 5927, pp. 610 - 613
DOI: 10.1126/science.1172525
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Reports

MESSENGER Observations of Mercury’s Exosphere: Detection of Magnesium and Distribution of Constituents

William E. McClintock,1,* Ronald J. Vervack, Jr,2 E. Todd Bradley,3 Rosemary M. Killen,4 Nelly Mouawad,4 Ann L. Sprague,5 Matthew H. Burger,4 Sean C. Solomon,6 Noam R. Izenberg2

Mercury is surrounded by a tenuous exosphere that is supplied primarily by the planet’s surface materials and is known to contain sodium, potassium, and calcium. Observations by the Mercury Atmospheric and Surface Composition Spectrometer during MESSENGER’s second Mercury flyby revealed the presence of neutral magnesium in the tail (anti-sunward) region of the exosphere, as well as differing spatial distributions of magnesium, calcium, and sodium atoms in both the tail and the nightside, near-planet exosphere. Analysis of these observations, supplemented by observations during the first Mercury flyby, as well as those by other MESSENGER instruments, suggests that the distinct spatial distributions arise from a combination of differences in source, transfer, and loss processes.

1 Laboratory for Atmospheric and Space Physics, University of Colorado, Boulder, CO 80303, USA.
2 Johns Hopkins University Applied Physics Laboratory, Laurel, MD 20723, USA.
3 Department of Physics, University of Central Florida, Orlando, FL 32816, USA.
4 Department of Astronomy, University of Maryland, College Park, MD 20742, USA.
5 Lunar and Planetary Laboratory, University of Arizona, Tucson, AZ 85721, USA.
6 Department of Terrestrial Magnetism, Carnegie Institution of Washington, Washington, DC 20015, USA.

* To whom correspondence should be addressed. E-mail: william.mcclintock{at}colorado.edu

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THIS ARTICLE HAS BEEN CITED BY OTHER ARTICLES:
Magnetic Twisters on Mercury.
K.-H. Glassmeier (2009)
Science 324, 597-598
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The Evolution of Mercury's Crust: A Global Perspective from MESSENGER.
B. W. Denevi, M. S. Robinson, S. C. Solomon, S. L. Murchie, D. T. Blewett, D. L. Domingue, T. J. McCoy, C. M. Ernst, J. W. Head, T. R. Watters, et al. (2009)
Science 324, 613-618
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