Lunar and Planetary Laboratory
University of Arizona, Tucson, AZ 85721
sprague
fax 520-621-4933
R.W.H. KOZLOWSKI
Physics Department
Susquehanna University
Selinsgrove, PA 17870
Lunar
and Planetary Laboratory
University of Arizona, Tucson, AZ 85721
dhunten
N.M. SCHNEIDER
University of Colorado, Boulder, CO
D.A. DOMINGUE
Lunar and Planetary Institute, Houston, TX
W. K. WELLS,
W. SCHMITT,
U. FINK
Lunar and Planetary Laboratory, The University of Arizona,
Tucson, Arizona, 85721
ABSTRACT
(Icarus, Volume 129, Issue 2, pp. 506-527.)
We report spectroscopic measurements of sodium in Mercury's atmosphere for
the period July 1985-May 1988. Na abundance varies from <1 x 10^10
atoms cm^-2 in equatorial regions in March 1987 to as much as ~1.5 x
10^12 atoms cm^-2 in May 1988. All observations were made using a
high-resolution echelle spectrograph on the 61-in. telescope on Mt.
Bigelow, Arizona. Strong high-latitude enhancements are common, with
the added characteristic that there is usually more at one hemisphere
than the other. There is an obvious diurnal correlation, with morning
abundances significantly higher than afternoon. We see notable Na
emission enhancements when our spectrograph slit is placed over the
radar-bright spots at 340 deg mercurian longitude and 55 degN and 25
degS latitude. We do not see any trend in column abundance with
increasing radiation acceleration. We do not see a significant
correlation of abundance with either solar F10.7 flux or sunspot
number. Other larger variations occur and must be caused by other
factors.