That is a funny way to put it. This sediment has a basaltic provenance, but it is no longer olivine basalt. Not since the original basalt has been weathered, eroded, transported, deposited, subject to diagenesis and yet further weathering.

Jon

It is now - Opportunity is about 160m SW of it. Two good driving days.

There was nothing interesting about Sputnik two years ago when they arrived, and there's nothing interesting about it now.

Doug

but it's on Mars- that makes it kind of interesting, doesn't it?

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So is everything. You have to make priorities. You could, by your argument, have spent the last 4.5 years taking 250,000 images of sky....after all, it's Mars right?

I hadn't noticed, till it was pointed out (at UMSF, of course), but this picture of little Sputnik crater in the foreground, with big ol' Victoria crater yawning wide in the background, has actually captured features of a third crater.

Way out on the horizon, way out, there are some peaks on the left, and some peaks on the right.

That's Endeavour Crater's rim.

Doesn't look so far. She'll be there in no time!

Edit: Now available at NASA Mars Exploration Rover Mission Raw Images :: Opportunity :: Navigation Camera :: Sol 1661

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The prevailing theory of the wall rock at Victoria and Endurance craters is that it is sandstone bedrock. I take that to mean it is thick sandstone rock perhaps meters thick produced over millenia by continual evaporative deposition.
I'm suggesting the sandstone is only a surficial layer at most a few centimeters thick and beneath it would be basaltic rock, with the sandstone surface layer being formed from aqueous alteration of the basaltic lava in the manner of pillow lava.
This would explain the presence of the basaltic sand which that LPI abstract I cited suggested there were no obvious sources for. I'm suggesting this basaltic sand comes from the basaltic rock beneath the sandstone layer.
One way to test this might be if the Opportunity rover ran over a smaller, protruding sandstone rock causing it to crack, thus revealing the composition of the rock inside.
There are some rocks in the vicinity of Sputnik crater this might be tested on.

Bob Clark

At least 150 meters behind Opportunity now.

See recent drive noted in article in Unmanned Spaceflight topic Opportunity Route Map.

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Rover imagery at Endurance and Victoria indicate that the sedimens are 10's of m thick, as a minimum. The satellite imagery indicates that the sedimentary succession at Meridiani is 100s of m thick. So there aren't doing to be basalts nearby. Under current martian conditions there is no reason why basaltic sand could not be transported by wind for 100s, even 1000s of km.

Jon

If the the sandstone was entirely submerged even for the wall rock than it would appear the sandstone was meters thick. This could still only be a surficial layer. The only way to find out would be dig centimeters down into the rock.
This image by Horton on the Marsroverblog.com site strongly implies the basaltic sand originates from inside the wall rock:



See the full size image here:

"super 3D panorama of northern Victoria rim on Meridiani Plain, Mars. Taken by Opportunity Feb 23-24, 2007 ( sol 1096-1097)"
http://www.flickr.com/photos/hortonheardawho/421241208/


Bob Clark

No it doesn't. Not even slightly. It implies that the basaltic sand is next to the wall. It could have trickled over the top blown by wind. It could have blown up to the wall from the crater floor.

Morphologically, minerologically, your volcanic obsession is totally unproven.

Doug is right. You would expect sand at the foot of a cliff to be the same composition as that on the plains. There might be some very local variations, compositionally and texturally caused by the changed aerodynamics, but they are going to be minor. You can test this at any area with windblown sand near where you live.

The well preserved bedding in the cliff is consistent with a sedimentary origin not volcanic.

Further the surface grains are moderately rounded and are well sorted, indicating extensive winnowing and transport. If they were locally derived you would expect see many more angular fragments, including hyper-angular glass shards, and overal poorer sorting.

It is fine to consider alternative hypotheses, but if they don't work you can't hang onto them.

Jon

The only thing imagery from orbit or from the surface can tell is what is on the surface. Even in the wall rock in craters you are still looking at only the surface. The only way to find out what's subsurface is by digging into the rock.
The prevailing theory is that the sandstone rock is built up in layers over millenia by successive deposition. But if that is true, why does not the layering extend all the way through into the rock? In cracks, the layering only seems to extend a few centimeters:



Bob Clark

And this one:



From this post:

Cape Verde.
http://www.marsroverblog.com/dyn/ent...ssion_page/209

Why does the layering only extend a few centimeters into the rock?

Bob Clark

Again - you're seing what you want to see. How do you know the layering only extends a few centimeters into the rock? You don't. Clearly erroded and visible layering is visible on the most exposed faces of the rock where wind has exposed them. Shadowed from wind in cracks and crevices, one would not expect to see similarly distressed surface features in there.

And guess what - if you want deep drilling into this rock - you've got it. You got it at Endurance, you got it at Victoria - nature doing the digging for you via impacts.

Doug

What Doug said, plus the fact thaat the outer surface and the surface in the cracks are in different weathering and erosional regimes so the surface texture is expressed differently. This is commonplace on Earth and Mars.

Did you notice the low angle cross bedding in the main cliff? These are the same as those seen in many other places at Meridiani where the rocks were tested with the RAT. Those rocks are sedimentary not volcanic.

Jon

End of the month means another Planetary Society Mars Exploration Rovers Update

Very long and detailed.

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Opportunity then headed toward an area the team named in honor of desert explorer Ralph Alger Bagnold. “It looked like the cleanest patch of Meridiani dust that we’ve seen anywhere,” said Steve Squyres, of Cornell University, the principal investigator for rover science. And the MER science team was anxious to determine its composition with its mineral detecting instruments.

Located on the lee side of the rim, the target was in “a little dust trap that also turned out to be a nasty little rover trap,” said Squyres. Opportunity slipped repeatedly trying to scale the ridge leading to the chosen target within Bagnold, Laubach said, so the MER team instructed the rover to abandon that assignment and rove on toward its next major destination.

“We did our best to get to Bagnold, but it became clear after a few sols that we were just wasting our time,” Squyres said. “We could try for months and never get to it, so it was time to go.”

Pity Ralph Bagnold is no longer around to give advice of desert travel!

Wikipedia hardly does justice to the career of this extraordinary human being. http://en.wikipedia.org/wiki/Ralph_Alger_Bagnold

See also:

http://www.weru.ksu.edu/symposium/pr...s/underwoo.pdf

http://www.geolsoc.org.uk/gsl/null/lang/en/page553.html

Jon

Spirit update (archive):

Nothing new

Opportunity update (archive):

sol 1655-1660, 24-Sep-2008: Road Trip Gets Under Way

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Spirit update (archive):

sol 1685-1689, September 28 - October 03, 2008: Spirit and Earth Stick Together

Opportunity update (archive):

sol 1661-1668, September 25-30, 2008: Opportunity Takes a Victory Lap

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