An ancient ocean on Mars once held more water than the Arctic Ocea on Earth, NASA scientists say, according to a press release from the W.M. Keck Observatory in Hawaii.
Scientists measured water in the Red Planet's atmosphere using the most powerful telescopes on Earth, which includes the telescope at the observatory. Their findings will be published in the journal Science on March 6.
Scientists estimate that the young planet Mars had enough water to cover its entire surface in about 450 feet of water, but it is more likely that the oceans covered half of the planet's surface and reached depths greater than a mile in some areas.
"Our study provides a solid estimate of how much water Mars once had, by determining how much water was lost to space," said Geronimo Villanueva, first author of the paper and scientist at NASA's Goddard Space Flight Center in Greenbelt, Md., according to the press release. "With this work, we can better understand the history of water on Mars."
Two types of water are present in Mars' atmosphere and they vary only slightly. The more familiar H2O (two hydrogen, one oxygen) is present as is HDO (one hydrogen, one oxygen and one heavier form of hydrogen, deuterium). By measuring the ratio of the two types of water, scientists can measure how much water has escaped into space.
The chemical signatures of the waters were distinguished by data from the Keck Observatory's 10-meter Keck II telescope, NASA's Infrared Telescope Facility in Hawaii and ESO's Very Large Telescope located in Chile. The team studied H2O and HDO over nearly six Earth years (about three Mars years). Seasonal changes and microclimates were revealed, even though Mars is basically a desert. The ratio maps produced are the first of their kind, according to the press release.
The polar ice caps of Mars are considered the planet's largest known reservoir of water and the water there is thought to hold evidence of Mars' evolution from the Noachian period, which ended about 3.7 billion years ago, to the present. The water at the polar ice caps is enriched eight-fold, according to the press release, therefore Mars must have lost a volume of water six-and-a-half times larger than what remains. Scientists believe Mars' primitive ocean must have been 20 million km3.
Judging from the surface of present-day Mars, water would have most likely be located in Northern Plains, because of the low-lying ground. An ocean there would have covered 19 percent of the Red Planet's surface (compared to the Atlantic Ocean which occupies 17 percent of Earth's surface).
"With Mars losing that much water, the planet was very likely wet for a longer period of time than was previously thought, suggesting the planet might have been habitable for longer," said Michael Mumma, a senior scientist at Goddard and the second author on the paper, according to the press release.
The new climate and atmospheric maps will provide a handy tool in the search for underground water on Mars.
Keck Observatory is a private 501(c) 3 non-profit organization and a scientific partnership of the California Institute of Technology, the University of California and NASA.
