Landslides unlike any on Earth
How to hide geology on Mars
June 27, 2016Where we have been
July 18, 2016
A Piece of Mars: Click on this 0.96×0.54 km (0.6×0.33 mi) scene to see it in detail. Many thin, narrow landslides have formed on these dust-coated hills. As far as I’m aware, there’s nothing like this on Earth. Inside the landslide scars, there are small dusty ripples about 1.75 m (~6 ft) in wavelength, smaller than the ripples found on dark sandy dunes. These landslides are visible in images at least as far back as 2007, although they clearly formed after the small crater on the slope (which is slowly being filled with the dusty debris). (HiRISE ESP_045605_1715, NASA/JPL/Univ. of Arizona)
1 Comment
Yes, there’s nothing like this on Terra. If the dusty hills were a dune then this could be interpreted as slip face avalanching. If there were a river or seashore eroding the bottom of the slope then this could maybe be interpreted as ongoing erosion, but its way too fast to be the result of Mars average erosion rate. The only non-extraordinary explanation available is that this is some kind of wind powered system that we don’t see on Earth, that is, that the wind is responsible for loading these slopes to the point where they can slide. I don’t think that there are any places on Earth where this is happening, despite there being lots of slopes and probably lots more sand movement on Earth than Mars. If slope wasting activity were extremely rare then there might be more explanations available, but its quite common. On Terran dunes avalanching can continue indefinitely because the dune moves across the landscape, but here we have to explain not only how the sand gets up the slope but also how it is removed from the bottom so that the whole process doesn’t over time gentle the slope to the point where it can no longer avalanche. There’s a tendency to think of these as special events, but they must be frequent, widespread and ongoing through geologic time or there would be no reasonable chance of seeing so many fresh ones.
Something like this sort of process is ongoing in miniature at all three rover sites. There’s no need to plan a special rover mission to slope streaks, RSLs, or slides of this present variety. The rovers have already ground-truthed many of these close up. There are about 10 good examples from Gusev, about 100 from Meridiani, and there must be more than 1000 now from Gale. Hence I’ve been trying to get people interested in the first scientific paper on this topic: Dickson, Head, and Kulowski out of Brown U in this year’s LPSC. They explain it as a wind driven process but they don’t seem to have much interest in the aeolian aspect. That’s where you come in, to prove or disprove that its wind driven. Whatever it is, its arguably the most active present day process on Mars.