In 2016, a VERY bright fireball fell over Arizona. When scientists examined pieces of it that fell to Earth, they found it look a *lot* like the rock that exploded over Chelyabinsk, Russia in 2013, the largest asteroid impact in over a century. https://www.syfy.com/syfywire/chelyabinsks-much-smaller-sibling-asteroid-fell-over-arizona-in-2016">https://www.syfy.com/syfywire/...

2/ It looks like the asteroid that fell in AZ in 2016 and the one over Chelyabinsk 3 years earlier were both chunks off a much bigger parent asteroid. Dating showed they formed at almost the exact same time, 4.47 billion years ago, presumably when the parent rock formed.

3/ They split off at different times though, likely from two different impacts on the parent asteroid. We can tell by examining how they’re affected by cosmic rays (subatomic particles in space). The longer they’re in space the more they’re affected.

4/ So 4.47 billion years ago the big asteroid formed. 11 million years ago it suffered an impact that blew off a small chunk (that eventually hit us in 2016), then 2 million years ago it happened again (and that much bigger piece hit us in 2013).

5/ The 2016 impact in AZ was from a rock roughly a meter across, and disintegrated 25 km above the ground. It left a trail of vaporized rock in the sky that got blown around by the wind and lit by the rising Sun, creating a truly gorgeous display called a “persistent train”.

6/6 We learn a lot about asteroids from studying meteorites. We figured out these two impactors were siblings, born of the same parent asteroid! Amazing. Sure, impacts can be dangerous, but they also tell us about the history of our solar system. Cool! https://www.syfy.com/syfywire/chelyabinsks-much-smaller-sibling-asteroid-fell-over-arizona-in-2016">https://www.syfy.com/syfywire/...