A sliver of Martian rock that once lay hidden in a university drawer has helped researchers better understand the Red Planet’s geological history. Using isotopic dating, a team at Purdue University has determined that the “Lafayette Meteorite” likely interacted with liquid water approximately 742 million years ago.

The study identified when water interacted with the meteorite and established that the dating was unaffected by events after it left Mars.

An asteroid struck Mars 11 million years ago and sent pieces of the red planet hurtling through space. One of these chunks of Mars eventually crashed into the Earth somewhere near Purdue and is one of the few meteorites that can be traced directly to Mars.