terminator. An examination of them shows no sodium emission visible. On 22 March 1989, in collaboration with Joseph Caruso, reticon scans were made using the 60-inch reflector of the Oak Ridge Station of the Smithsonian Astrophysical Observatory. Preliminary results indicate no sodium emission was visible at the pole, although a higher resolution repeat of the experiment is desirable. I have also scanned archival spectra for traces of lunar polar sodium emission with no success. In addition, in a private communication A. E. Potter indicates he measured less sodium emission at the poles than the small amount measured at the subsolar point [39]. Direct detection of hydrogen emission from cosmic ray, micrometeorite and geomagnetic tail perturbed solar wind proton bombardment of pristine ices in the permanently shadowed lunar craters may also be possible. If the mass function of hydrogen in cometary ices is /H, where AfT is the mass of regolith normally vaporized by incoming meteorites each second. Using AfT=0.146 g cm'^*1, from Morgan et al. (op. cit.) then AfH=0.01 g cm~2s-1~6.0x 1021 H atoms cm"2s"'. For hydrogen, the mean lifetime is short; approximately 1 X 102 sec is a reasonable estimate, before ejection from the lunar atmospere. The hydrogen alpha filter experiment could detect a 5% average difference in readings for a difference in column density of 7.9 X 1022 H atoms cm-2 in the Balmer excited state-, but since the excited states are not sufficiently populated, this method of searching for direct hydrogen emission is marginal at best. It would be far better to examine the Lyman alpha emission in the ultaviolet, and International Ultraviolet Explorer images SWP-34028-34031, taken on 6 August 1988, were recently located in the archives. A preliminary inspection of the images, taken at the lunar limb, shows no enhancement of Lyman alpha emission from that in the geocorona background, although a more detailed study is planned. Conclusions Lunar ices at the poles of the moon cannot be ruled out because of the low sensitivity of these experiments and the uncertainties of ice sources (TLP, Nemesis episodic commentary bombardment rates, etc.). Indirect evidence of the lunar ices’ existence, using Earth-based experiments, have proved negative. The low level of observed sodium emission, and the agreement of the observed ratio of potassium and sodium emission intensities with the expected ratio deduced from the lunar rock composition, and the fact that maximum emission occurs at the equator, indicate that emission source materials originate in the lunar rocks, and regolith, and not cometary recondensates. There is not yet any evidence that lunar polar ices exist. ACKNOWLEDGEMENTS This work was supported by a Space Studies Institute Contract. I have benefitted from discussions with B. Hapke, W. Cassidy, N. Sanduleak, W. Farrand, J. Caruso, D. Amon and G. Knox. Additional financial and material assistance was provided by W. Babich, C. Havey, The University of Pittsburgh, Case-Western Reserve University and Kent State University. I also thank a reviewer for many constructive comments.
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