According to a March 28, 2014 story in Inside Science, researchers have concluded that Mars contains as much as one tenth of the Earth’s oceans in water at that planets’ poles and in as yet undiscovered deposits of ice beneath the Red Planet’s surface. Most of Mars’ water, however, escaped within the first half billion years of its life due to the fact that its gravity was not strong enough to retain its atmosphere.
“Still, scientists think most of the water on Mars probably escaped because the planet's gravity was not sufficient to hold onto its atmosphere. Over time, the water on Mars evaporated and drifted away into space.
“To estimate how much water was lost this way, the researchers measured the ratio of two forms of hydrogen found in Martian meteorites that landed on Earth. Ordinary, common hydrogen contains one proton in its nucleus. Deuterium is a heavier form of hydrogen, with one proton and one neutron. Water that includes at least one deuterium atom instead of regular hydrogen is heavier.
“With this added heft, water that contains deuterium can't escape Mars' gravity as easily as water made of regular hydrogen. As a result, most of the water that left Mars is of the lighter variety. So by comparing the amounts of deuterium and hydrogen, the researchers can determine how readily water was escaping Mars. A higher deuterium-to-hydrogen ratio means greater water loss.”
Because of the findings of various Mars probes, particularly the Mars Curiosity, scientists have already concluded that Mars had running water on its surface billions of years ago. But since most of the water, along with the Martian atmosphere, left relatively early in Mars’ existence, the question arises, was that sufficient time for life to have evolved? Scientists have speculated that microbial life may have existed on Mars during its warm, wet period. Fossilized remains or even living organisms may still exist in the subsurface ice. Thus far no definitive proof has been found for either ancient Martian life of modern survivors.
Water with deuterium, also known as “heavy water,” is used in nuclear experiments and other applications, though it is not itself radioactive.