Scientists at Aix-Marseille University in France believe they have identified the world's first-known "boomerang meteorite." They think the Earth rock got tossed into space, where it spent thousands of years before returning home.
The reddish-brown stone was found in the Sahara Desert by meteorite hunters in 2018. Nicknamed "Northwest Africa (NWA) 13188," it was initially thought to be an ordinary meteorite. However, an analysis by Jérôme Gattacceca and his team revealed that it had qualities of both Earth and space rocks.
NWA 13188's structure is similar to that of volcanic stones found on Earth. However, its "fusion crust" is usually reserved for meteorites. When space rocks encounter the Earth's atmosphere, the air around them gets very hot. This causes the rock's outer layer to melt, creating this so-called "fusion crust."
Additionally, the presence of isotopes on the rock indicates it was exposed to cosmic rays — high-energy particles from space. The level of isotopes suggests the stone had been drifting through space for at least 10,000 years before falling to Earth.
The researchers have two theories about how NWA 13188 may have reached space. It could have been thrown from a massive volcanic eruption. The other, more plausible, explanation is that the rock flew out of the Earth's atmosphere when a giant asteroid slammed into our planet.
Gattacceca's team presented their findings at a geochemistry conference in France on July 11, 2023. They intend to conduct further analysis to determine NWA 13188's exact age. They are also trying to find evidence of a giant impact crater from which the rock may have originated.
But not all scientists are convinced NWA 13188 is a "boomerang meteorite." Frank Brenker, a geologist at the Goethe University Frankfurt in Germany, thinks NWA 13188 could also have come from another part of the solar system. The expert told Space.com, "I think there is no doubt that this is a meteorite. It is just a matter of debate if it is really from Earth."
Interestingly, this is not the first time scientists have found an Earth rock in space. A stone found during the 1971 Apollo 14 mission to the Moon had mineral fragments from Earth. The researchers speculated it got thrown out to the Moon billions of years ago, when the satellite was much closer to our planet.
Resources: Space.com, Livescience.com, CNN.com