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A. Cook, M. Gibbens (U. Nottingham)
Although the Moon is considered to be geologically dormant, surface altering events visible to orbiting spacecraft must still occur, albeit infrequently e.g. fresh impact craters detected from Apollo imagery. Given a surface area of 3.8E7 km2 and the 40 year time frame spanning Lunar Orbiter to SMART-1 missions, it is likely that 10's-100's of surface changes measurable in the > 50m scale range may be detected by automatically comparing temporal images of the same areas under similar (< 5 deg difference) incidence and emission angles. Automated tie-pointing and image footprint overlap detection developed from Clementine stereo research can be used to select suitable overlapping temporal image pairs of a given area. These can then be automatically registered/warped together, photometrically calibrated to each other and subtracted to leave a difference image. Differences that exceed 3 standard deviations across the image can then be compared to the most recent mosaics of optical maturity in order to confirm whether a suspected area of change is aligned with fresh non-spaceweathered parts of the surface. Knowledge that could be gained from such a study could include: 1) confirmation of cratering rate assumptions that were made from the Apollo ALSEP seismometers, 2) identification of surface disturbances by ejecta from impacts detected by Apollo seismometer, or Earth based telescopic impact flash observations; these can then be used to help relate estimated impact energy to crater size, 3) the areal extent of dust transport from impact ejecta, landslides, or other suspected mechanisms such as residual outgassing or electrostaic levitation of dust. All three of these have important implications for future surface based exploration in identifying sites of interest that can be either monitored over time to study the progression of space weathering, or for studying freshly excavated underlying geology.
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Bulletin of the American Astronomical Society, 37 #3
© 2004. The American Astronomical Soceity.