Houston (PTI): Mars interior is more colder and solid than previously thought, suggests an analysis based on new images sent by a NASA spacecraft in orbit around the Red Planet.

"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. "This implies that the planet's interior is more rigid, and thus colder, than we thought before," said Phillips, the lead author of the report appearing in the online version of journal Science.

He suggest any liquid water that might exist below the planet's surface and any possible organisms living in that water, would be located deeper than scientists had suspected. The discovery was made using the Shallow Radar (SHARAD) instrument on NASA's Mars Reconnaissance Orbiter, which has provided the most detailed pictures to date of the interior layers of ice, sand and dust that make up the north polar cap on Mars.

"In our first glimpses inside the polar ice using the radar on Mars Reconnaissance Orbiter, we can clearly see stacks of icy material that trace the history of Mars' climate," said co-author of the paper Jeffrey Plaut, from NASA's Jet Propulsion Laboratory in Pasadena, California. In March scientists had announced the detection of the first ever image of active avalanches on Mars near the Red Planet's north pole.

On May 25, NASA's Phoenix Mars Lander is scheduled to touch down not far from the north polar ice cap. It will further probe the history of water on Mars, and is expected to get a close look at ice on the planet, the ScienceDaily online said.