Image courtesy of Livio L

Age dating by crater counting

Apollo samples were radiometrically dated allowing

Image courtesy of Livio L. The method is based upon the assumptions that a new surface forms with zero impact craters, and that impact craters accumulate at some constant rate. Know one of these variables and you can constrain the other.

The Tycho crater antipode deposit covers a smaller area, but the deposits are pervasive and appear to be dominated by impact melts. Instead, we assess the relative ages of surfaces from the density of impact cratering and gain absolute ages based on Apollo samples.

Crater count isochrons have been constructed for every body in the inner solar system and, with more caution, for outer solar-system bodies as well. These calibrated surfaces allowed crater counting to be used as a chronometric tool with greater confidence, firstly to date the rest of the unsampled lunar surface. The expansion continues even to the present day.

The technique was also pioneered by Gene Shoemaker Shoemaker et al. After mare rocks had been radiometrically dated, these calibrated surfaces were the key to using crater counting to date other planetary bodies. The method has been calibrated using the ages of samples returned from the Moon. There was rapid expansion at first thereafter it slowed down.

Based on experimental work, Hartmann and pers. Apollo samples were radiometrically dated, allowing the averaged cratering rate to be estimated much more accurately. After that the star we call the sun and the planets revolving it formed and evolved. This region has been identified previously, using radar and imaging data.

Based on experimental work