Lead author Geronimo Villanueva at NASA’s Goddard Space Flight Center and his team used infrared spectrographs on ground-based telescopes – the European Southern Observatory’s Very Large Telescope, the W M Keck Observatory and NASA’s Infrared Telescope Facility in Hawaii – to measure the relative proportions of hydrogen and deuterium in water at Mars.Ocean water on Earth has about 3200 molecules of H2O for every HDO molecule; martian water was lost to space through processes that preferentially affect the lighter molecule, leaving the water remaining on Mars much richer in HDO. The greater the water loss, the higher the ratio of HDO to H2O in the remaining water.

Villanueva and his team mapped Mars for six years (three martian years) and found surprising variations: microclimates and seasonal changes. They found that atmospheric water near the poles was enriched in HDO by a factor of seven compared to water on Earth, and polar ice enriched by a factor of eight.

Together these suggest that the planet lost 6.5 times more water than is currently in the ice caps, making an ocean of at least 200 million km3 in the Noachian period. If this had occupied the low-lying Northern Plains, comparable in area to the Atlantic, it would have been more than 1.9km deep in places.

This work highlights the power of ground-based telescopes to study planetary processes. It also suggests that Mars may have had a much longer period as a wet and potentially habitable planet.

Source: Daily Galaxy