May 23, 2007, HiRISE release Options

[Guest_AlexBlackwell_*]

May 23, 2007, HiRISE release

[dvandorn]

Actually, Stu, I think the lightened area looks roughly the same in terms of the extent of duning as the rest of the surrounding terrain. It looks more to me like the lightened area has seen more deposition than the surrounding terrain -- the underlying lava-flow surface is more muted and softened in the lightened area.

I think what's happening here is that the prevailing winds are coming from the bottom of the image. As they pass over the hole, the air sinks a bit, and winds strike the rim of the hole along the top arc (all directions -- top, bottom, etc. -- relate to the orientation of your posted image). So the top arc of the rim is being eroded a little more rapidly than the rest of the rim, and the erosion product (basaltic dust, most likely) has been deposited on the ground beyond the top rim arc.

It's also at least somewhat possible that winds are entering the hole, swirling around, eroding the interior of the lava tube, and blowing dust out from the cavern and onto the ground above the top rim arc. I just don't think that Martian winds are powerful enough to reach into such a deep hole and scoop dust out of it, but I could be wrong. At any rate, it's impossible to model airflow into and out of that hole without having a decent idea of the size and shape of the empty lava tube, and we really have no way of determining that...

-the other Doug

[Stu]

Actually, Stu, I think the lightened area looks roughly the same in terms of the extent of duning as the rest of the surrounding terrain. It looks more to me like the lightened area has seen more deposition than the surrounding terrain -- the underlying lava-flow surface is more muted and softened in the lightened area.

Ok, just me then!

I did think first about airflow over the crater being responsible for the change in brightness, but I can't help wondering if there are other - smaller, so as yet unseen - holes in this area and they're all linked together... would that allow winds to be generated within a tunnel network leading to a higher-than-usual speed for winds coming up out of a hole like this? Please, no-one cuff me around the ear for asking that if it's impossible or stoopid, I'm just thinking aloud...

And talking about smaller holes... anyone taken a closer look at these dark spots?



No sign of lighter "streaks" above them, so maybe I'm just seeing holes that ain't there... or maybe they are holes that just aren't big enough to generate much airflow...

As I said, just thinking aloud...