Distribution of Crater Clusters on Mars

N. G. Barlow (Univ. Central Florida)

Crater clusters are defined as groups of small craters, generally consisting of 10 or more craters less than 1- to 2-km-diameter, which overlap and thus are presumed to have formed simultaneously. Traditionally, crater clusters have been interpreted as secondary craters from large impacts, but Magellan imagery revealed crater clusters on Venus formed by a different mechanism. On Venus, impacts generally less than about 15-km-diameter are not single craters but clusters of smaller craters, produced when the meteoroid broke up during passage through the thick venusian atmosphere. On Mars, a large number of crater clusters exist, not all of which are readily identified with a primary impact crater. In 1994, Hartmann and colleagues proposed that such isolated crater clusters on Mars may result from the breakup of weak cometary bodies as they passed through either the current thin atmosphere or through a previous thicker atmosphere (Hartmann et al., 1994, BAAS, 26, pg. 116).

We have undertaken a study to determine the distribution of crater clusters across the martian surface. The study is identifying which crater clusters are secondaries from larger impacts and which are isolated from such impacts. For the isolated crater clusters we are estimating their time of formation to determine if any consistency among formation ages can be found. This study will determine if crater clusters can be used as indicators of climatic change during recent epochs on Mars.