MADISON, Wis. (AP) — Scientists at the University of Wisconsin-Madison are helping search for evidence of alien life not by looking into outer space, but by studying some rocks right here on Earth.

Some of the rocks are up to 3.5 billion years old. The scientists are looking for crucial information to understand how life might have arisen elsewhere in the universe and guide the search for life on Mars one day.

"There's a story always hidden in rocks," said geoscientist Clark Johnson, the lead investigator for the Wisconsin Astrobiology Research Consortium. "... It's up to (geologists) to be clever enough to find the tools that we need to interrogate those rocks to find what story they preserve."