Mars has bright polar caps of ice that are easily visible from telescopes on Earth. A seasonal cover of carbon-dioxide ice and snow is observed to advance and retreat over the poles during the Martian year. Scientists using radar data from NASA’s Mars Reconnaissance Orbiter (MRO) have found a record of the most recent Martian ice age recorded in the planet’s north polar ice cap.
This image is a simulated 3-D perspective view of Chasma Boreale, a canyon that reaches 570 kilometers (350 miles) into the north polar cap. It was created from image data taken by the THEMIS instrument on NASA’s Mars Odyssey spacecraft. Canyon walls rise about 1,400 meters (4,600 feet) above the floor of Chasma Boreale. Where the edge of the ice cap has retreated, sheets of sand are emerging that accumulated during earlier ice-free climatic cycles. Winds blowing off the ice have pushed loose sand into dunes, then driven them down-canyon in a westward direction.
Image Credit: NASA/JPL/Arizona State University, R. Luk