... Mars . ... Observing . ... Mars' cold insides . ... The discovery was made using the Shallow Radar instrument on the spacecraft, 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," says Jeffrey Plaut of NASA's Jet Propulsion Laboratory....