Lunar Surface: Changes in 31 Months and Micrometeoroid Flux

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Science  04 Dec 1970:
Vol. 170, Issue 3962, pp. 1092-1094
DOI: 10.1126/science.170.3962.1092


Comparison of pictures of the lunar surface taken 31 months apart by Surveyor 3 and Apollo 12 show only one change in the areas disturbed by Surveyor: a 2-millimeter particle, in a footpad imprint, that may have fallen in from the rim or been kicked in by an approaching astronaut. Vertical walls 6 centimeters high did not collapse and dark ejecta remained dark. No meteorite craters as large as 1.5 millimeters in diameter were seen on a smooth soil surface 20 centimeters in diameter; this indicates a micrometeoroid flux lower than 4 x 10-7 micrometeoroids per square meter-second at an energy equivalent to about 3 x 10-8 gram at 20 kilometers per second. This flux is near the lower limit of previous determinations.

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