For only the second time in history, scientists have detected an incoming asteroid, watched it burn up in the atmosphere, and then collected a piece of it from the ground.
This asteroid called 2018 LA collided with Earth on June 2, exploding over the skies of Botswana and seen by people on the ground. But it wasn’t until Saturday June 23 that an international team of scientists tracked down part of the meteorite, in Botswana´s Central Kalahari Game Reserve (CKGR).
"The challenge was to search for a meteorite in 200 square kilometers [77 square miles] of uncharted wild in a park teeming with elephants, lions and snakes,” Professor Alexander Proyer from the University of Botswana, who led the expedition, said in a statement.
The asteroid had been spotted just eight hours before it hit Earth, by the University of Arizona’s Catalina Sky Survey. It exploded just seconds after entering the atmosphere, appearing as a bright fireball in the sky.
But the fragments from the explosion were scattered by the wind, making the collection of debris from the impact difficult. After five days of searching, the team found the first meteorite, which they can now study to see what the asteroid was made of. And they’re still looking for more fragments, too.
It’s thought the asteroid was about 2 meters (6.5 feet) across, which made it especially hard to detect. Meteors of this size can only be seen about a day before they hit, but it’s estimated that about six of this size hit our atmosphere every year. To spot them, telescopes need to be looking in the right place at the right time, as they move so fast.
For that reason this is only the third incoming meteor we’ve spotted before it hit Earth. And, as mentioned earlier, it’s only the second from which we’ve also found pieces on the ground. The first, called 2008 TC3, came back in 2008, with researchers finding hundreds of pieces scattered over northern Sudan.
Discovering an asteroid, predicting its impact, and recovering pieces of it has been called a “perfect asteroid trifecta”. By studying it, we can tell where it came from and what other asteroids from that origin might be made of. This may be important for planetary defense in the future if we ever spot a sizeable asteroid heading our way.