Mars Odyssey data reveals possible water ice near Martian equator
High levels of hydrogen detected could exist within subsurface water ice.

By Laurel Kornfeld | 5 hours ago

Researchers who reprocessed data captured by NASA's Mars Odyssey orbiter between 2002 and 2009 discovered a region of abundant hydrogen near the Martian equator that could indicate the presence of subsurface water ice.

Through image-reconstruction techniques used to sharpen images collected by spacecraft, the scientists boosted the spatial resolution of the data from 320 to 180 miles (520 to 290 km), a process that team leader Jack Wilson of the Johns Hopkins University Applied Physics Laboratory (JHUAPL) in Laurel, Maryland, compared to reducing the altitude of the orbiter by 50 percent.

"It gave us a much better view of what's happening on the surface," Wilson said.

Specifically, the technique revealed signs of hydration in Martian equatorial regions along the path of eroded deposits known as the Medusa Fossae Formation, particularly in areas up to 600 miles (1,000 km) wide between northern lowlands and southern highlands containing materials that are loose and easily eroded.

The initial data was collected by Mars Odyssey's neutron spectrometer, an instrument not capable of directly detecting water. Yet scientists can use its measurement of neutrons to determine the presence of hydrogen, which could be a sign of either water or other materials containing the element at the location.

In 2002, Mars Odyssey discovered sub-surface hydrogen at Mars' upper latitudes, suggesting the site has either water or other substances containing hydrogen.

Since hydrogen is believed to not be thermodynamically stable at Mars' lower latitudes, scientists determined its presence there is in the form of hydrated materials, minerals created by inorganic chemical reactions between water and their crystal structures.

Six years later, NASA's Mars Phoenix lander, which touched down near the planet's north pole, confirmed that hydrogen there exists within water ice.

If water ice does exist beneath the surface near the equator, future astronauts would have a Martian water supply that could be used for both drinking and production of rocket fuel, reducing the mass of cargo that has to be brought from Earth.

Scientists currently cannot explain how subsurface water ice could persist in Mars' equatorial regions over long periods of time.

One theory proposes that between several hundred thousand to several million years ago, Mars had a greater axial tilt, causing a mix of dust and ice from its polar areas to travel through its atmosphere.

Another possibility is that humidity below the surface kept water ice trapped there.

But neither theory explains how the water ice could have remained beneath the surface for such a long time.

"Perhaps the signature could be explained in terms of extensive deposits of hydrated salts, but how these hydrated salts came to be in the formation is difficult to explain. So for now, the signature remains a mystery worthy of further study, and Mars continues to surprise us," Wilson said.

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