More info on the Chelyabinsk asteroid has been revealed:
- The object started forming from molten droplets 4.56 billion years ago, just after the solar system started coming together.
- Over the next 10 million years it gathered together enough dust particles to become an asteroid around 60 miles wide.
- "Shock veins" in the rock show it had a major impact 125 million years after the solar system started forming.
- Between 4.3 and 3.8 billion years ago it absorbed many more shocks during the late heavy bombardment.
- Two more impacts occurred in the last 500 million years.
- 1.2 million years ago, a final impact created the 65 foot wide (20 meter) rock which hit Chelyabinsk in February.
The Chelyabinsk asteroid that landed on Earth was once part of a bigger body known as the LL chondrite parent body, and was probably buried several kilometers beneath the surface of this object.
Other fragments of the LL chondrite are still known to researchers to exist in space, including the 540m asteroid Itokawa, which a Japanese spacecraft visited in 2005.