The Moon-forming collision would have been only one such "giant impact" and, perhaps, the last.

The Argyre basin was created by a giant impact.

It is also possible that terrestrial planets had magma oceans at some point during their formation as a result of giant impacts.

This giant impact also gave the Earth its axis tilt and velocity of rotation.

But a 2008 study provided additional research that supports a single giant impact.

When did the giant impact that formed the Moon take place?

"I guess it could be what's left of a planet or moon that got clobbered by some giant impact," Guitierrez said.

But Ms. Johnson said it came down to this: "Where do you have the opportunity to have a giant impact?"

This supports the idea that Charon was created by a giant impact into Pluto's icy mantle.

The giant impact believed to have formed Caloris may have had global consequences for the planet.