The mother of meteorites

When something hit Vesta, an enormous hunk of rock in the asteroid belt, it created one of the largest impact craters known, the highest mountain in the Solar System, and many of Earth’s meteorites.

4 Vesta asteroid, source of many of Earth's meteorites
NASA/JPL-Caltech/UCLA/MPS/DLR/IDA, Public domain, via Wikimedia Commons

Vesta is the second-largest asteroid in the asteroid belt. It’s not huge – less than 600 kilometres long – but it casts a rather big shadow over the Solar System.

About a billion years ago, something hit Vesta. Something big. We don’t know precisely what it was, but it punched a fairly sizeable hole in Vesta. The collision left an impact crater on the asteroid’s south pole… well, actually, that crater is large enough to cover most of Vesta’s southern hemisphere. The crater is called Rheasilvia, and it is one of the largest craters in the Solar System.

Vesta rotates
NASA/JPL-Caltech/UCLA/MPS/DLR/IDA; Little Mountain 5, Public domain, via Wikimedia Commons

Rheasilvia is 505 kilometres around. By comparison, the Chicxulub impact crater under Mexico is 150 kilometres around… and that’s the one that probably killed off the dinosaurs 66 million years ago. So this crater on Vesta is enormous. And not only is it wide, but Rheasilvia is deep: up to 13 kilometres down. The collision that created it may have even pierced the asteroid’s mantle, it went that deep.

Right in the middle of the crater is a mountain. From the crater floor it goes up an estimated 22.5 kilometres, which makes it the tallest mountain we know of. It’s five hundred metres taller than Olympus Mons on Mars:

Highest mountain in the Solar System
NASA / JPL-Caltech / UCLA / MPS / DLR / IDA / PSI, Public domain, via Wikimedia Commons

This impact was so huge that it kicked up a whole cloud of mini-asteroids known, appropriately, as the Vesta family. We know of more than 15,000 of them. Every now and then Jupiter flies past and knocks some of them out of their orbit. And some of those asteroids end up falling to Earth.

The bits of Vesta that get as far as our planet are known as the HED meteorites. They are a bit weird because they look a lot like local igneous rocks. These rocks, however, were formed on an asteroid far far away, blasted into space by one of history’s most epic planetary-level collisions, shoved out of their comfortable asteroid belt home by the gravity of Jupiter, and then scoured by Earth’s atmosphere on the way down.

Quite a trip.

One Reply to “The mother of meteorites”

Leave a Reply