A meteorite named Northwest Africa 13188 has made an extraordinary journey through space, according to a recent study presented at the geochemical Goldschmidt Conference in France.
Discovered in Morocco in 2018, the object left Earth's gravitational pull only to return to it. Weighing 646 grams, its chemical composition is close to that of terrestrial volcanic minerals. But the rock also contains helium-3, beryllium-10 and neon-21, suggesting it has been exposed to cosmic rays.
Scientists therefore believe that the rock is of terrestrial origin, but flew into space before returning to crash into our planet.
"Therefore, we consider NWA 13188 to be a meteorite, launched form the Earth and later re-accreted to its surface," explain the researchers in a press release.
It remains to be seen how this rock was transported into outer space. The hypothesis that it was ejected after a volcanic eruption remains to be verified. Volcanic plumes usually don't rise more than 50 kilometers, so it seems unlikely that an eruption could eject a rock into space.
A Terrestrial Rock on the Moon
While a meteorite's round trip to Earth would be a unique event, terrestrial rocks have been found on other celestial bodies. In 1971, the Apollo 14 mission discovered the oldest terrestrial rock ever found – on the Moon!
The 4-billion-year-old object could be a remnant of the Hadean Eon, the oldest division of geologic time. It could have been thrown into space by the impact of a comet or asteroid, an event that sent matter through Earth's primitive atmosphere.
The rock would then have found its way to the Moon, which was three times closer to our planet 4 billion years ago.