`Earth was bombarded by asteroids 3-4 billion years ago`

Analysing tiny "spherules" embedded in layers of rock, a team from the Purdue University in the US said they found the "first real solid evidence" of asteroid bombardment.

Tiny ‘spherules’ tell tale of Earth’s asteroid impacts

The spherules were created when asteroids crashed into the Earth, vaporizing rock that expanded into space as a giant vapour plume.