What makes astronomers think that impact rates for the Moon must have been higher earlier than 3.8 billion years ago?
A) all the radioactive rocks found on the Moon so far give ages much younger than that, so the Moon must have formed less than 3.8 billion years ago
B) we see many more craters on the Moon that have been eroded by wind and rain
C) all the large craters on the Moon come in pairs, while all recent craters are single
D) there are ten times more craters on the older highlands than the younger maria
E) the ancient sea basins on the Moon, whose water has since evaporated, show a lot more cratering
Section 9.4: Origin of the Moon

Question

Quizplus · Accepted Answer

There are ten times more craters on the older highlands than the younger maria, suggesting that impact rates on the Moon were much higher earlier than 3.8 billion years ago.

What Makes Astronomers Think That Impact Rates for the Moon