PSP_002208_1755_1.0xA Piece of Mars: Two-toned ripples have formed on a steep slope, created by winds rushing downhill (from top to bottom in this frame). The larger ones are big ripples, with peaks more than 30 meters apart. What makes them unusual, however, is stark contrast between the dark (bluish) upwind side and the light (pale tan) downwind side. How did that happen? It’s because sand blowing downhill preferentially scours the dark upwind side of the ripples, leaving the downwind side untouched. (PSP_002208_1755, NASA/JPL/University of Arizona)

Comments (3)

  1. Hi Lori. For some time now I’ve been struck quite strongly, when viewing Mars photos, by the vertical distortion or exaggeration of the geological features. I then realized that the lower gravity would have the effect of increasing or steepening the angle of slope failure, and went searching for papers on the subject. Sadly, it doesn’t seem to be acknowledged in any of the internet media publications. I think it is an exciting point of connection for general Mars enthusiasts! I’ve only found one paper that seems to deal with the subject, and then google finally brought me here, and as well as just found & watched “Sand Seas of the Solar System – Lori Fenton (SETI Talks)” which I thoroughly enjoyed! Could you point me to any other current sources or papers dealing with Mars and/or Planetary Geology? It would be much appreciated!!

    1. Actually the features aren’t really distorted. The angle of repose (at least to first order) isn’t dependent on gravity, so mass wasting slopes are roughly the same angle on Earth, Mars, and the moon. A good place to get started is an online text Geomorphology from Space ( To browse the surface of Mars, I recommend Google Mars (part of Google Earth), or if you want a little more flexibility, look up JMARS (free software that lets you view nearly all of the released data from orbiting spacecraft). Let me know if you’re hungry for more than that and I’ll find some more references for you!

      1. Hi Lori, Thank you so much for the links! I installed JMars, which is an amazing tool, but life without CRISM integration is like a day without sunshine… and so applied for said. Maybe Santa will visit while I’m becoming comfortable with JMars operation. One can only dream 🙂

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