No. 56: Mar-Apr 1988
More information has surfaced on the enigmatic lunar swirl markings (Category ALE5 in our catalog: The Moon and the Planets. These whitish blotches are not only visually incongruous, being obviously different from the debris spla shes around craters, but they also exhibit curious magnetic properties. J.F. Bell and B.R. Hawke, of the University of Hawaii, have acquired near-infrared spectra of the swirl designated Reiner Gamma. They report that the composition of the swirl material does not match the crater ejecta; and, also, that a previously undetected reddish halo surrounds the swirl. Best guess at present: The swirls are the scars of comets -- probably less than 100 million years old. (Anonymous; "Cometary Scars on the Moon," Sky and Telescope, 75:11, 1988.)
Comment. Does nearby earth also bear cometary scars? Some think that the 1908 Tunguska Event was a cometary impact. (See ETC2 in our catalog: Caro lina Bays, Mima Mounds.) Also see the the item below under GEOLOGY about comets and the earth's oceans.
Reference. Both catalog volumes mentioned above are described here.