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We knew Mars was cold, but new observations from the Mars Reconnaissance Orbiter indicate that the crust and upper mantle of Mars are stiffer and colder than previously thought. And scientists say any liquid water that might exist below the planet’s surface, and any possible organisms living in that water, would be found deeper than anyone suspected.
“We found that the rocky surface of Mars is not bending under the load of the north polar ice cap,” said Roger Phillips of the Southwest Research Institute in Boulder , Colo. Phillips is the lead author of a new report appearing in this week’s online version of Science. “This implies that the planet’s interior is more rigid, and thus colder, than we thought before.”
MRO’s Shallow Radar instrument has provided this new information on the interior layers of ice, sand and dust that make up the north polar cap on Mars. The radar images reveal long, continuous layers stretching up to 600 miles (1,000 kilometers) with a flat border between the ice cap and the rocky Martian crust. On Earth, the weight of a similar stack of ice would cause the planet’s surface to sag. The fact that the Martian surface is not bending means that its strong outer shell, or lithosphere — a combination of its crust and upper mantle — must be very thick and cold.
“The lithosphere of a planet is the rigid part. On Earth, the lithosphere is the part that breaks during an earthquake,” said Suzanne Smrekar, deputy project scientist for MRO. “The ability of the radar to see through the ice cap and determine that there is no bending of the lithosphere gives us a good idea of present day temperatures inside Mars for the first time.”
This news is especially intriguing since the Phoenix spacecraft will land on the Red Planet on May 25 to investigate Mars’ north polar region.
The radar pictures also reveal four zones of finely spaced layers of ice and dust separated by thick layers of nearly pure ice. Scientists think this pattern of thick, ice-free layers represents cycles of climate change on Mars on a time scale of roughly one million years. Such climate changes are caused by variations in the tilt of the planet’s rotational axis and in the eccentricity of its orbit around the sun. The observations support the idea that the north polar ice cap is geologically active and relatively young, at about 4 million years.
Original News Source: JPL Press Release