What’s a permafrost tunnel? To find out, follow Madeline Ostrander as she enters one of only two in the world. Madeline (@madelinevo) reports for Undark from the underground science lab dug into frozen earth, just north of Fairbanks, Alaska. In some places, the tunnel yields samples more than 43,000 years old. (And watch for an upcoming book from Madeline: madelineostrander.net) image: Public Affairs Office Fort Wainwright