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J. A. Grier, A. S. McEwen, R. G. Strom (Lunar and Planetary Laboratory), P. G. Lucey (University of Hawaii)
In order to ultimately determine the flux of impactors onto the lunar and the terrestrial surface in recent (~600 Ma) time, believable, absolute ages for 100 or more bright, rayed craters on the lunar surface are needed. Ideally, absolute ages can be determined by obtaining samples from each crater, radiometrially dating them, and then extrapolating an impactor flux. Realistically, it is clear that only a small number of the larger lunar craters can and will be radiometrically dated in the foreseeable future. On the other hand, a large number of relative ages can be generated by examination of lunar spacecraft spectral data with near global coverage. The Clementine color data set provides global lunar coverage and appropriate spatial resolution to undertake such a survey. The Optical Maturity Parameter (OMAT) developed by Lucey and colleagues is a tool for assisting in the determination of the relative ages of bright rayed craters. An extensive survey of bright rayed craters down to small sizes (1km or less) is in progress using the Clementine color data. A relative crater chronology will eventually be generated using several tools, including superpositioning of rays, OMAT images, age estimates based on superposed craters, estimates for the rates of soil maturization, and corrections for systematic biases in the data. The radiometric ages from known craters included in the survey hopefully will allow this relative chronology to be constrained absolutely, and a crater flux to be generated. Such an endeavor, if sucessfully carried out, would have far-reaching significance in understanding recent/future cratering on the Earth and Moon, and in the interpretation of cratered surfaces and crater chronologies. References: McEwen, A., Moore, J., and Shoemaker, E. (1996) JGR. Lucey, P., Taylor, J, and Hawke, B. (1998) JGR, In press Lucey, P., Taylor, J, and Hawke, B. (1998) LPS XXIX, #1356, LPI, CDROM. Grier, J. et al., (1998) LPS XXIX #1905, LPI CDROM. Eliason et al., (1998) Multispectral Mapping of the Moon by Clementine, abstract in ``New Views of the Moon," LPI.