"These images show that there's more activity on Mars than we may have thought," Craig Kochel of Bucknell University said. "I don't think anyone thought about this at all too much before HiRISE." The avalanches look similar to "dry avalanches" he has seen at Alaska's Wrangell mountains, where ice and snow mix with debris and come thundering off a near-vertical rock cliff. And they too can be incredibly active; when Kochel and his research team visited the Wrangells in the summer of 2006, they witnessed almost 300 avalanches in just eight days. The Wrangell avalanches are similar to the Martian ones in that they are both relatively dry. Unlike many avalanches on Earth that are mostly snow, they are mostly ice. But there are important differences. For one, Martian slides tend to be mostly fine grains of dust and snow that form large clouds. The ice in the Wrangell avalanches often comes in large, heavy chunks. Earth's gravity and thick atmosphere also mean that terrestrial avalanches are thunderous, powerful slides that can flatten trees and sturdy buildings. Martian gravity is three times weaker and its atmosphere 100 times thinner, by contrast. "The avalanches we're seeing wouldn't have nearly as much oomph as ones on Earth," Russell said. Related Links: Mars Reconnaissance Orbiter's high resolution camera, HiRISE |
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