Mars: Ice Block Avalanche

Image credit: NASA/JPL-Caltech/Univ. of Arizona

One of the most actively changing areas on Mars are the steep edges of the North Polar layered deposits. This image from NASA's Mars Reconnaissance Orbiter (MRO) shows many new ice blocks compared to an earlier image in December 2006. An animation shows one example, where a section of ice cliff collapsed. The older image (acquired in bin-2 mode) is not as sharp as the newer one.

HiRISE has been re-imaging regions first photographed in 2006 through 2007, six Mars years ago. This long baseline allows us to see large, rare changes as well as many smaller changes.

Source / Image Courtesy

The north polar ice cap of Mars appears like a gigantic spiral out of ice and snow. Dark troughs in which wind-transported dust and deposits accumulated, alternate with white, ice-covered mounds.

A particularly striking dark trough is Chasma Boreale, to be seen in the midterm of the movie. It is an up to 100 kilometer wide and 500 kilometer long canyon that cuts two kilometers deep into the north polar ice cap.

Flight Over Chasma Boreale At The Martian North Pole.

The images show layers of water ice and dust possibly for the first time in perspective view. Chasma Boreale is cut into the layered material that lies beneath the water ice of the polar cap.

For decades, these layered materials were assumed to consist of a mixture of ice and dust. Recent observations could mean that some of the layers are a source for windblown sand.

The floor of the trough and the caldera-like structures are covered by dark sand dunes. This dark material could be volcanic ash or it is possible that it is dark sand eroding out of the polar layered materials.