Finding Evidence of ET

February 13, 2013 - 12:31 PM
In this Jan. 22, 2013 photo University of Wisconsin-Madison Geoscientist Clark Johnson holds what he says is a 3.5 billion year old rock in Madison, Wis. Johnson is leading a team of scientists and others studying Earth rocks that are billions of years old 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. (AP Photo/Carrie Antlfinger)