Most meteorites are very old. Solid chunks of matter were typically formed a few billion years ago, and the ones that didn’t coalesce into a planet became nomads, drifting aimlessly through space. For example, the Allan Hills 84001 meteorite (or ALH84001) is believed to be over4 billion years old—a relic from the formation of our Solar System.
But it’s not famous for being one of the oldest things in our neighborhood. Discovered in Antarctica in 1984, ALH84001 was studied extensively for eight years before researchers made a shocking announcement: It was covered with carbonate globules, a sign that it could be a collection of bacteria fossils. That’s particularly strange, considering it came from Mars. It’s believed that about 15 million years ago, the impact from another meteorite knocked this chunk into space, along with a colony of Martian bacteria. It floated around in space for a while before connecting with our planet roughly 13,000 years ago.
The claim that the rock was covered in alien bacteria was later bashed to bits by the scientific community. But in 2011, it was confirmed that even if bacteria never lived on the rock, it was definitely formed in anenvironment with liquid water.