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Mars Reconnaissance Orbiter maps out hidden ice
by Ian Randall
Posted: 5 March 2010

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Significant volumes of buried ice have been discovered in the mid-latitudes of Mars’ northern hemisphere, according to a report presented at the 41st Lunar and Planetary Science Conference earlier this week.

Subsurface ice was first discovered by the Mars Reconnaissance Orbiter two years ago. Two hundred and fifty separate observations of the study region, which is around the size of California, have been made by the orbiter using the craft’s Shallow Radar instrument. Study of the data has revealed that hidden ice appears to be quite a common phenomenon.

The Shallow Radar instrument on NASA's Mars Reconnaissance Orbiter has detected widespread deposits of glacial ice in the mid-latitudes of Mars. Image: NASA/JPL-Caltech/ASI/University of Rome/Southwest Research Institute.

“We have mapped the whole area with a high density of coverage. These are not isolated features. In this area, the radar is detecting thick subsurface ice in many locations,” says Jeffrey Plaut, of NASA’s Jet Propulsion Laboratory.

The ice, which makes up a large proportion of the non-polar ice on the red planet, was seen to be most common around the bottom of cliffs and slopes, or found trapped in craters and other such valleys.

In the rough terrain of Deuteronilus Mensae, a region of Mars which lies halfway between the equator and the low plains of the pole to the north, the underground ice deposits can be seen reaching out for hundreds of kilometres. Plaut and his colleagues have drawn up a map of the confirmed ice deposits, which was presented at the conference, held in The Woodlands, Texas, across this week.

It is now possible to advance theories as to the origin of this ice, and it is believed that the deposits may have been emplaced by the retreat of regional ice sheets.

Illustration of the Mars Reconnaissance Orbiter's Shallow Radar device in action. Image: NASA.

“The hypothesis is the whole area was covered with an ice sheet during a different climate period, and when the climate dried out, these deposits remained only where they had been covered by a layer of debris protecting the ice from the atmosphere,” Plaut says.

The Shallow Radar instrument, or SHARAD for short, uses a frequency varying subsurface sounding radar to enable high resolution imaging of the top kilometre of Mars surface. SHARAD, which has been in operation over Mars for three years, was developed by the Italian Space Agency, in conjunction with California’s Astro Aerospace, who developed the antenna.

The next immediate step in the research will be to continue increasing the extent of the mapped region – but with the possibility of this ice containing environmental footprints from its time of deposition, it seems quite possible that these hidden treasures might be targeted for extraction and study by future space missions.