2. Characterize the diversity and extent of different types of basaltic volcanism.

A meteorite impact can create a crater in which the material comprising the central peak rises from a depth equal to about 10 percent of the crater's diameter, and so provide sub-surface sampling. The rim can come from a depth equal to about 5 percent of the crater's diameter. The central-peak material of Tsiolkovsky crater, a farside crater pictured here, was originally at a depth of about 20 km.

Basalts are the most common type of rock cooled from lava. Samples of basalts from the Moon's nearside, collected during Apollo and Luna missions, represent partial melts of the lunar mantle which occurred about 400-1000 million years after the crust and mantle separated into two distinct layers. However, remote sensing tells us that the basalts we have sampled represent only about a third of those on the lunar surface, and that there is great diversity in basalt composition and age, implying diversity in the mantle. The mineral character of basalts is best observed in the freshly exposed material surrounding small craters, which requires the kind of high spatial resolution of which M³ will be capable.