Gaspra's Cratering History.

Kurzfassung

The images of the asteroid 951 Gaspra obtained by Galileo show impact craters down th the resolution limit. The observed crater population resembles very much the size-distributions seen on the inner solar system planets. The crater frequencies in the 1km-range on Gaspra can be used to infer the age of Gaspra by relating the present-day large-body (d>&#6150km) asteroid impact probability to the large craters in a lunar-like production size-frequency distribution.Cratering rates for 1km-craters on Gaspra can be reliably calculated.The only assumption is that a lunar-like crater size-frequency distribution also holds for the asteroid belt. The resulting age, accounting for all uncertainties in scaling for the impact conditions on Gaspra, ranges between 120 and 800 million years, most likely between 250 and 500 m.y., when the parent body of the Flora family, a member of which Gaspra is, was shattered.