what makes astronomers think that impact rates for the moon must have been higher earlier than 3.8 billion years ago? a.the ancient sea basins on the moon, whose water has since evaporated, show a lot more cratering b.all the large craters on the moon come in pairs, while all recent craters are single c.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 d.there are ten times more craters on the older highlands than the younger maria e.we see many more craters on the moon that have been eroded by wind and rain

Astronomers are scientists in the field of astronomy, who focus their research on a particular problem or area outside the realm of the Earth. Observe celestial bodies such as stars, planets, moons, comets, and galaxies either by observation (by analyzing data) or by theoretical astronomy. Examples of topics and fields studied by astronomers include planetary science, solar astronomy, the origin and evolution of stars, and the formation of galaxies. A related but different field is physical cosmology, which studies the universe as a whole.

Therefore, Option (4) is correct: There are ten times more craters on the older highlands than the younger maria.

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