How well do we know the Moon? Perhaps not as well as we thought; scientists just found 222 new craters on our nearest celestial neighbour -- 33 per cent more than we thought were there.
The research used footage from the Lunar Reconnaissance Orbiter to improve our estimates of the rate at which craters form, which turns out to be more frequently than we thought. They also found out that impacts that form craters can cause secondary craters to form too, a process which is churning up the top two centimetres of the Moon's surface at a rate 100 times faster than we thought.
The new study gives some 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 used high-resolution temporal "before and after" imaging from the Lunar Reconnaissance Orbiter Camera Narrow Angle Camera, covering many "patches" of the Moon to give an accurate number to the current crater production rate.
They detected 222 new impact craters accounting for 33 per cent more craters (with a diameter of at least 10 metres) than current models predicted.
They also identified broad "reflectance" zones associated with the new craters and interpreted these zones as evidence for a new impact process involving surface-bound jets of material. This is the secondary cratering process they identified, churning the regolith -- the layer of unconsolidated solid material on the surface -- more than 100 times faster than previously thought.