This composite graphic illustrates the use of the Shallow Radar
instrument on NASA's Mars Reconnaissance Orbiter for mapping
underground ice-rich layers of the north polar layered terrain
on Mars. Pane "a" is a radargram from the instrument, showing a
cross-section of Mars' north polar cap, based on time lags of
radio-wave echoes returning from different layers. The
penetrating radar reveals icy layered deposits overlying a basal
unit in some areas. The vertical dimension in the cross-section
is exaggerated one-hundred-fold compared with the horizontal
dimension. The vertical scale bar is one kilometer (3,281 feet).
The horizontal scale bar is 100 kilometers (62 miles). Pane "b"
is an image from the High Resolution Imaging Science Experiment
camera, also on NASA's Mars Reconnaissance Orbiter. It shows the
layered deposits and the basal unit in outcrop exposed near the
edge of the polar cap. The scale bar is 2 kilometers (1.24
miles). This is a cutout from an observation taken on taken Nov.
28, 2006, at 83.4 d