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New data from a six year study of the water in the modern Martian atmosphere have allowed scientists to estimate the amount of water Mars once had.
About four billion years ago, the young planet would have had enough water to cover its entire surface in a liquid layer about 140 metres deep, but it is more likely that the liquid would have pooled to form an ocean occupying almost half of Mars’s northern hemisphere, and in some regions reaching depths greater than 1.6 kilometres. “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, a scientist working at NASA’s Goddard Space Flight Center in Greenbelt, Maryland, USA, and lead author of the new paper.
The image on the right is an artist’s conception of the oceans that would have existed on Mars, based on modern elevation data.
I must note that this conclusion, the size of the lost Martian ocean, is based on the assumption that the isotope ratios of Martian water started out the same as the Earth’s. While this is a reasonable assumption, it does not have to be true. Nonetheless, these conclusions, using ground-based telescopes, do match up with similar data obtained by Curiosity.