Ancient Aliens: STRANGE STRUCTURE DISCOVERED ON MARS (Part 1) (Season 16) | History

Watch all new episodes of Ancient Aliens, Fridays at 9/8c, and stay up to date on all of your favorite History Channel shows at A strange keyhole-shaped formation protruding from Mars may directly correlate to a similar structure on Earth - Theorists believe extraterrestrials built these to signal humans, in Season 16, “The Galactic Keyhole.“ #AncientAliens Subscribe for more from Ancient Aliens and other great HISTORY shows: Find out more about the show and watch full episodes on our site: Check out exclusive HISTORY content: History Newsletter - Website - Facebook - Twitter - “Ancient Aliens“ explores the controversial theory that extraterrestrials have visited Earth for millions of years. HISTORY® is the leading destination for award-wi