Video: Measuring Mars' ancient ocean

Scientists believe that an ancient Martian ocean held more water than the Arctic Ocean on Earth. It once covered what is now the planet's arid northern plains and would have contained at least 20 million cubic kilometers (12.4 million cubic miles) of water. That was during the planet's wet Noachian period, which ended about 3.7 billion years ago when life was just emerging on Earth, according to NASA Goddard. This new picture of early Mars raises the odds for the possibility of ancient life existing on the Red Planet.