NASA astronauts who visited the Moon during the Apollo 14 mission hauled back a whole bunch of material from its surface. At the time, they believed they were bringing Moon rocks and dust so that scientists could learn more about Earth’s friendly little neighbor, but as it turns out they were actually bringing some Earth material back to where it originated.

In a new study published in Earth and Planetary Science Letters, researchers reveal that one of the chunks of rock brought back by Apollo 14 was actually a piece of the early Earth that had been blasted into space by some kind of impact several billion years ago.

A close inspection of the rock revealed that it was made up of a variety of materials that are abundant on Earth but are rarely found on the Moon, including quartz and zircon. They believe the conditions under which the rock formed would have matched those of Earth rather than the Moon, but how exactly did the rock make it so far from home?

“The clast was ejected from the Earth during a large impact, entrained in the lunar regolith as a terrestrial meteorite with the evidence of reducing conditions introduced during its incorporation into the Imbrium ejecta and host breccia,” the study explains.

To put it a bit more simply, the rock was a piece of Earth that was shot skyward after something quite large slammed into the planet at high speed. It was ejected into space and subsequently collided with the Moon, spending billions of years on its surface and becoming integrated into the planet before astronauts just happened to stumble across it, snagging it for study back on our planet.

It’s a remarkable discovery, and an interesting glimpse into the life of the early Earth. Scientists have long believed that a young Earth was under bombardment from space debris as the Solar System continued to form, and this appears to be some very good supporting evidence.