[X] My Assistant

[Zelenyikot]

Little veins in Shaler on Sol 322

Attached thumbnail(s)

 

[SFJCody]

http://astrogeology.usgs.gov/news?id=news/...nhoff-road-trip

We have started the long traverse to the base of Mt. Sharp (Aeolis Mons), the long-term goal of the mission! It may take a year to get there, depending on how many interesting features we find along the way. The challenge for the science team will be to identify the most important targets along the way, and to study them without delaying drive progress too much. Today we are planning targeted observations, followed by another drive over the weekend.

Here we go then! Mountain bound! Looks like a new thread may be in order, too.

[ngunn]

If a fossilized dune is of a lighter color than more active dunes because of accumulation of the ubiquitous red surface dust, wouldn't that tend to make the fossilized dunes more reddish than bluish?

That's what I thought at first, but maybe there are two processes at work. When the dune first stabilizes maybe it 'bleaches' relatively quickly due to some process other than dust accumulation.

Curiosity is unlikely to visit that feature so unless there is a similar one close to the place where our traverse threads through the dunes it may not give us a definitive answer. It's probably not a priority question, but fun to think about all the same.

EDIT: It could just be a different kind of bedrock as Phil and Doug have suggested, but then you still have to explain why it remains free of the ubiquitous red dust.

[Gerald]

EDIT: It could just be a different kind of bedrock as Phil and Doug have suggested, but then you still have to explain why it remains free of the ubiquitous red dust.

Many more factors will influence color and specularity, e.g. grain size, local wind (dust removal below saltation threshold for sand), surface texture, adherence properties of the surface, abrasion by saltating sand grains during storms.
If we can fix all other parameters, assume low abrasion but high local dust removal, and the dune is made of basalt sand, it might be worth to check, whether color can change from grey to reddish-brown like weathering basalt on Earth. That's at least plausible in an oxidizing environment.

Paper on reflectance/specularity
Abstract on abrasion by saltating particles on a crust.
In-depth paper about dust adherence.
Wikipedia about basalt (including oxidation)

[Guest_Actionman_*]

-------------

If we can fix all other parameters, assume low abrasion but high local dust removal, and the dune is made of basalt sand, ...

"If" being the key word. "IF" the dark dune is segregated basalt sand, where is the basalt the sand coming from? directly under the dune?