What is the evidence for the late heavy bombardment?

Question

all i could think of was planets whose surfaces are completely covered in craters, but that could also mean that the planet was just really old.

can somebody help out?

also, was it the Oort cloud that caused the late heavy bombardment?

thanks.

Answer 1

We can see craters on Mars and Mercury, but do not have the information to date them.  We have dated some of the craters on the moon by radiometric dating of returned moon rocks.  The late heavy bombardment thought to have occurred on earth is based on an analogy with the moon, and the very reasonable assumption that the earth, with its stronger gravity, would have been even more effective at attracting bombarding objects.

Not really the Oort cloud, which is formed from leftover icy material, but presumably mainly rocky material, similar to that from which the rocky planets themselves aggregated.

The idea is that towards the end of accretion, there would have been a lot of reasonably large objects getting mopped up by collision with the newly formed planets.