31st Annual Meeting of the DPS, October 1999
Session 18. The Moon and Mercury Posters
Poster Group I, Monday-Wednesday, October 11, 1999, , Kursaal Center

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[18.04] A Lunar Transient Event in Cobrahead

S. B. Calkins, B. J. Buratti, J. K. Hillier, T. H. McConnochie (Jet Propulsion Laboratory, Caltech)

The Clementine spacecraft returned over 2 million images of the Moon during its two-month mapping mission. These images provide an unprecedented opportunity to closely scrutinize reports of lunar transient phenomena (LTP) on the Moon. During the main mission, a team of amateur astronomers mobilized to provide nearly continuous visual coverage of the Moon. In at least 4 cases, Clementine images were obtained before and after reports of LTP reported by ground-based observers. We have inspected the before and after images obtained by Clementine for all 4 events(1). For one case occurring near the Cobrahead feature on the Aristarchus plateau, there is good quantitative confirmation on Clementine images for the LTP observed from ground. On 1994 23 April, ground-based observers reported a "possible obscuration over Cobrahead; rest normal" between 03:50 and 04:30 UT(2). An analysis of the Clementine images taken on 1994 3 March and 27 April show a measurable difference in color. The images obtained on April 23 exhibit a ~15 increase in color ratio (0.4 to 1.0 microns) when compared to the images acquired on March 3. The Aristarchus plateau is one of the youngest areas on the Moon: if any residual lunar activity exists, it is reasonable to search for it there. The Cobrahead, which is a collapsed lava tube, is an area where many past observations of LTP have been reported. These include a reddish-orange brightening lasting at least 25 minutes(3). (1) Buratti, B. et al., 1999, submitted to Icarus. (2) Cameron, W. et al., 1996, The Strolling Astronomer 39, 145. (3) Greenacre, J., 1963, Sky Telesc. 26, 316.

Work funded by NASA.

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