There's a whole lot about our own planet that we've not yet explored. After years of data, scientists have announced the discovery of a 460 mile long canyon underneath Greenland's ice sheet. It's longer than the Grand Canyon, and no human has ever laid eyes on it before.

The canyon is hidden by a thick layer of ice, and the half mile deep canyon was discovered by an ice penetrating radar. According to Jonathan Bamber, professor of physical geography at the University of Bristol:
Scientists were able to send out radio waves that would travel through the ice, bounce off the bedrock underneath, and come all the way back up. Meaning the longer a radiowave takes to come barreling back, the deeper that particular bit of canyon is.

[NASA]