This was a surreal place for meteorite hunting. Bat foxes and warthogs sauntered by, lions secretly chased and slaughtered giraffes, while leopards lazed in trees. Guards from the Botswana Ministry of Wildlife and National Parks protected the search party in the event that a fangled predator came too close to comfort itself. The meteorites also looked a lot like animal droppings, which meant the team was frequently bamboozled by coproological cheaters.
“It was a completely unusual experience for all of us,” said Mr Gabadirwe.
It wasn’t until June 23, the last day of the first search mission, that the first meteorite was found – a small piece of the star weighing less than an ounce. It was named Motopi Pan after a local watering hole. “It became a national treasure of Botswana, this little stone,” said Dr. Jenniskens.
The compositions of the meteorites were matched to those found on Vesta using data from NASA’s spacecraft Dawn. Dawn is now orbiting the dwarf planet Ceres lifelessly after there was no more fuel at the end of 2018. It documented the geology of Vesta from 2011 to 2012. Scientists confirmed this original history by reverse engineering the asteroid’s terrestrial trajectory.
Cosmic rays shape tracks on asteroids by changing atomic nuclei. The traces of these meteorites indicated that the asteroid that crashed to Earth was bathed in this radiation for 22 million years as it traveled to Earth. That meant that a 22-million-year-old impact crater would mark the point where this asteroid was released from Vesta.
A six mile long crater called Rubria on Vesta was the best candidate. The surprising lack of contamination from the asteroid’s solar wind – the stream of plasma and particles coming from the sun – suggested that the asteroid’s material was shielded from space for billions of years. Unlike another similarly aged crater, Rubria sat undisturbed on top of a hill, a quiet 2018 LA spot was able to stay buried before an impact released it.
“The study is all about cosmic drama,” said Katherine Joy, a meteorite expert at the University of Manchester in England who was not involved in the work. However, linking 2018 LA to a specific location on Vesta relies on many underlying assumptions, so no one can be sure that Rubria is the right place.
For now, scientists will continue to observe the heavens and explore the deserts of the earth in hopes of finding more insightful fragments of our cosmic cradle’s past. Meteorite hunts “are always incredible adventures,” said Dr. Jenniskens – a grueling, but exciting way to spend a lifetime.
