I know I am not at my blogging best when I just write, “hey, look at these spectacular images!” But…look at these spectacular images!
An image-of-the-day gadget on my iGoogle home page showed me this picture, which I subsequently spent about a half hour trying to locate at a primary-source web site. It is wicked cool.
Click to go to this image’s description page on the University of Arizona HiRISE site. (Be sure to bookmark the 2560×1600 wallpaper version!!!)
I really want to know how these terraced buttes got to be the way they are…it looks like they must have been eroded in stages, with each layer from the top getting peeled back successively, but somehow the individual layers hold together – those are some pretty steep walls. I can see in the southwestern portion of this image that some of the terrace walls are eroding away in chunks; there are a couple good fallen boulders over there. The layers might be some kind of sandstone, because they haven’t eroded away in lots of rocks and boulders, so they don’t seem very friable, but there’s obviously a lot of source material for dunes in this area so the butte walls might be getting ground down into very small grains. I’m not sure what the fluvial history of Arabia Terra is – on Earth, that would be bound to play an important role in creating landforms like this.
I also really love the expression of the more recent aeolian features in this area. Looks like there are prevailing north-south winds on the east side of this image (I’m going to say the wind blows to the north because the north sides of the dunes look more like slip faces to me), but from the east-moving dunes in the terraced valley-like feature at center bottom and the east-west oriented ripples on the larger dune field, the winds are apparently going in rather circuitous routes around these buttes. There are also some confusingly-oriented dunes and ripples in the southwest portion of this image, probably from the wind winding around all the rocky towers. (In my mind, I can hear it whistling.)
Looks like the valley from which the east-going dunes have traveled is an exposed outcrop of one of the terrace layers. This image can resolve objects less than a meter in size, so the various crisscrossing dark lines in the light-toned outcrop might be joints or something.
Anyway, this is not a new image and I haven’t studied or researched this stuff…I just saw it today and wrote a little stream of consciousness of geological ideas. I just think this image looks beautiful and I want to send some rovers/people there. Any planetary science guys want to comment?
Last, and just for grins, here are some goodies I turned up in my search for that image on the UA HiRISE site. Here we have some dramatic contrast between dunes and some lighter, rockier topographically high areas:
Here’s some great layer exposures around some hills – and if you zoom into the large version of this one, you can find some wild and interesting ripple patterns:
Thus ends today’s amateur geology geekage.
2 thoughts on “Planetary scientists have all the fun”
Planetary scientist, reporting for duty!
Your summary is pretty much right. The cyclic bedding is caused by alternating strong and weak layers, and the fact that there are boulders coming from some of the steep slopes supports this: tough material forms big boulders and cliffs, weak material tends to just crumble into finer particles that can be carried away by the wind.
I would hesitate to say for sure that the aeolian materials are being sourced from the buttes here, but it’s possible.
I think there are some thoughts that the rocks of Arabia Terra are part of an extensive altered tephra deposit that extends up to Mawrth Vallis, one of the proposed MSL sites, but I don’t know whether the rocks shown here are thought to be part of that sequence. There’s an abstract about the observed alteration available here: http://www.lpi.usra.edu/meetings/msr2008/pdf/4052.pdf
Arabia Terra is definitely one of the more scenic areas of Mars. Some of my favorite MOC images are of the layered formations there: http://www.msss.com/mars_images/moc/dec00_seds/8N7W/, http://martianchronicles.wordpress.com/2008/11/15/mars-art-something-old-something-new/
Thanks, Ryan! Any idea if there’s a DEM for that part of Arabia?