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March 26, 2012

Rocks on Mars

Garden of the Gods
We know a lot about rocks, and the ways they react to wind, water, sunlight, heat, and other factors. Geologists can look at a strange rock formation, such as Colorado's Garden of the Gods, at tell you exactly what happened to create these odd structures. However, as with all science, there's always more to discover. The newest discovery is of a completely new kind of landform... on Mars.

This new kind of structure is called a periodic bedrock ridge. This sounds quite technical, but in reality, that is exactly what the structures look like: ridges in the bedrock at a regular (or periodic) distance from each other. In fact, it looks quite similar to sand dunes, at a first look. However, instead of being grains of sand blown into piles by the wind, they are tracks eroded by the wind into the bedrock. 

Periodic Bedrock Ridges
From Science Daily
David Montgomery, of the University of Washington, suggested that these features formed because the rock has bands of softer material within it, and that the erosion is of an unusual sort, that works perpendicular to the wind direction. The hypothesis is that the high speed winds on Mars are thrown into the air when they collide with a solid land formation, and that these periodic bedrock ridges form when the winds return to the surface. In order to visualize this, imagine driving a remote-control car. Jump it off a ramp, and onto a memory-foam type surface. The place where it impacts will have deeper tire tracks than anywhere else. That car is like the wind on Mars, and that impact point is where Montgomery and his team believe the ridges form.

This research is particularly interesting because there don't seem to be any analogs, to date, of this kind of feature on our own planet. On Earth, the presence of water means that very rarely will bedrock be eroded by wind alone. This difference means that we can understand not only Mars geology better, by utilizing these landforms to look at the beds in the Martian surface and figure out more about the geologic history of the planet, but also understand better how erosion works and parse out, here on Earth, the differences between different types of erosion, and the characteristics that separate one from another.