More than 200 new craters on the Moon - 33 per cent more than predicted in current models - are identified in a new study in Nature this week. The study provides insight into the impact-cratering process as well as the rate of crater formation on the Moon, which is important when dating rock units on the Moon and other terrestrial bodies.
Although previous studies of existing craters and samples from the Moon provided information on the process of crater formation and the past rate of cratering, less has been known about the present crater formation rate.
Emerson Speyerer and colleagues use high-resolution temporal ‘before and after’ imaging from the Lunar Reconnaissance Orbiter Camera Narrow Angle Camera covering many patches of the Moon to quantify contemporary crater production rate. They detect 222 new impact craters accounting for 33 per cent more craters (with a diameter of at least 10 metres) than current models predict. They also identify broad reflectance zones associated with the new craters and interpret these zones as evidence for a new impact process involving surface-bound jets of material. They estimate that this secondary cratering process is churning the top 2 centimetres of regolith - the layer of unconsolidated solid material on the surface - more than 100 times faster than previously thought.