Martian water may be ice in planet's interior
BY JEFF FOUST
Posted: December 28, 2000
Liquid water that once flowed on the surface of Mars could now be locked up deep in the planet's interior as an unusual form of ice, scientists reported earlier this month.
On Earth, such ice would form in deep ocean trenches, such as near the Pacific Ocean island of Tonga, where temperatures and pressures would permit the formation of ice VII. The ice would then be carried into the planet's interior in subduction zones, where one portion of the planet's crust is pushed beneath another.
In most cases the ice would melt as it was carried into warmer regions of the planet's interior and recycled back to the surface through volcanism. However, Bina said that as a planet cools, the ice would last longer and be carried to greater depths. "Some of the ice might never get warm enough to melt, and the ice could accumulate in the interior," he explained. "The 'doomsday scenario' would be a planet so cold that all of the water eventually accumulated as ice in the interior, leaving no water behind on the surface."
Planetary scientists had believed that Mars' water either was lost to space through bombardment or thermal escape, or was locked up near the surface in the form of permafrost or ordinary ice deposits. Bina believes that it's possible some or all of the water could be in the form of ice VII deep within the planet.
"Water for forming gullies could be stored at shallow levels beneath the Martian surface, perhaps as normal ice," he said. "Our work suggests that there could also be water stored in the deep interior as high-pressure ice, which could be released to drive volcanic activity."
Determining whether any Martian water is stored within the planet as ice VII may require detailed seismological or geochemical studies. "One could look for it with seismology, as ice will have a different seismic velocity than rock," said Bina.