In February 2013, a previously undiscovered space rock exploded over the sky of Chelyabinsk, a city in West-Central Russia. The shockwave from the meteor injured almost 1,500 people and videos of it were shared across the world. Now analysis of the meteorite left behind suggests that the space rock might have formed at the very beginning of the Solar System.
Minerals inside the meteorite were damaged in the collisions of this space rock and provide clues as to its formation. The findings are reported in the journal Communications Earth & Environment.
The youngest signature for this kind of collision event is from less than 50 million years ago. In that event, the minerals cracked but the impact did not have incredible pressures or temperatures. It was a lesser impact, although it put it on its fateful collision course to Earth.
More interesting is the much older collision the study evidences. This is from less than 4.5 billion years ago. That’s an important time in the history of our planet. That’s about the time when the Mars-sized planetoid Theia is believed to have slammed into Earth, thrown material into orbit, and formed the Moon.
“Meteorite impact ages are often controversial: our work shows that we need to draw on multiple lines of evidence to be more certain about impact histories – almost like investigating an ancient crime scene,” lead author Craig Walton, from Cambridge’s Department of Earth Sciences, said in a statement.
The team carried out Uranium-lead dating. Uranium radioactively decays into lead over time and by measuring the quantity of either, researchers can date features in the meteorite, especially those that formed following the collisions that this object experienced.
“The question for us was whether these dates could be trusted, could we tie these impacts to evidence of superheating from an impact?” said Walton. “What we’ve shown is that the mineralogical context for dating is really important.”
Other stony meteorites, in the same class as the Chelyabinsk one, have indicated high-energy collisions between 4.48 and 4.44 billion years ago. This is telling us something very important about that formative movement in the history of our corner of the Universe.
“The fact that all of these asteroids record intense melting at this time might indicate Solar System re-organisation, either resulting from the Earth-Moon formation or perhaps the orbital movements of giant planets.”
Better understanding of the formation of these objects as well as the formation of the Moon itself would provide important insight into how our planet came to be.