[X] My Assistant

[jvandriel]

Spirit is now almost at the bottom of Inner Basin.

Time to start a new topic.

Here is a 360 degree panoramic view taken with the L0 navcam on Sol 667.

jvandriel

Attached thumbnail(s)

 

[Bob Shaw]

Hmmm... Since you got me interested in this, I went back and noticed that there were lines at the previous drive location (AJW6). They were interested enough that they did a 2x2 pancam mosaic of this zigzag pattern as well as (I think maybe) a second Navcam sweep around the rover to see if there were any more.

   

2N186997821EFFAJW6P1985L0M1.JPG

2N186820199EFFAJW6P1605L0M1.JPG

Has anyone said the magic word 'polygon' yet? Or 'frost heave'?

I wonder where we are with respect to any possible water table - perhaps there are areas of ice-saturated soils, forming isolated playas? Lenses?

Bob Shaw

[atomoid]

From looking at the anaglyph you can see how steep the terrain drops off this little ridge, perhaps that has something to contribute to the linear features. well, maybe not.

Sure, ice sapping (or alternatively, slow mineral de-hydration shrinkage over the eons) would tend to contract the subsurface leaving these features as the subsurface faults develop, but these look to be only several decades old, the sand is transported much too fast for these features to persist, especially given all the dust devil activity.

So there has to be some process that is regenerating these features either seasonally (near-surface freezing/thawing cycles) or maybe this is the result of some episodic change (in other words, did we just get lucky here and stumble upon the results of some recent faulting that took millions of years to finally occur in this geologic moment? and these features will soon be erased for all eternity).

Personally, i like the idea of subsurface ice sapping, both here and a Meridiani, to explain the faulting and "frost-heaved" sand mounds at the polygon boundaries. Its simple and doesnt seem too far-fetched given what we now know. But what other evidence would that produce? should we be seeing more pervasive results of such a process? The clouds at Meridiani may have been formed from outgassing subsurface moisure when the conditions were just right. Maybe they just havent been right at Gusev for clouds.

[jamescanvin]

For those of you who might not have noticed (it's been so long you might not be checking any more!)

Steve has a new update

[alan]

From Steve's latest update

On Mars, Spirit is well down off of Haskin Ridge and heading for Home Plate. On the way, we've stopped off at three big outcrops, named Larry's Bench, Seminole, and Algonquin. Algonquin is the one that we're parked at now. They're all similar to one another, and all dramatically different from anything we've seen anywhere else. The rocks have undergone very little alteration, and contain a lot of olivine... much more olivine than we've seen anywhere else.

If I remember correctly large amounts of olivine mean these outcrops have been exposed to little water.

[mike]

Woah. Thanks for the heads-up.

[general]

http://qt.exploratorium.edu/mars/spirit/na...2EP0715L0M1.JPG

I'm a bit lost here:

Would this be "Miami" (aka Way Point)? Or perhaps Comanche?

[Guest_Sunspot_*]

WOW..... look at the thin ridge like feature running in front of Spirit in this navcam sequence.

http://qt.exploratorium.edu/mars/spirit/na...2EP0715L0M1.JPG

http://qt.exploratorium.edu/mars/spirit/na...2EP0715L0M1.JPG

I've never seen anything like that at Spirits site before.

[mhoward]

[alan]

http://qt.exploratorium.edu/mars/spirit/na...2EP0715L0M1.JPG

I'm a bit lost here:

Would this be "Miami" (aka Way Point)? Or perhaps Comanche?

Its Miami, Comanche is visble to its left in mhoward's upper image.

[mhoward]

From Steve Squyres latest update:

Next stop should be Comanche, a big and very red outcrop between us and Home Plate. It looks like Comanche may be different from Algonquin and the rest, based on Pancam and Mini-TES data... we'll see what we see when we get there.

Although I bet now they'll stop and look at the feature Sunspot pointed out first.

[RNeuhaus]

From Steve's latest update

If I remember correctly large amounts of olivine mean these outcrops have been exposed to little water.

Indeed, it is only as a clue but not yet as a SURE YES. The olivine presence on the rock means that it was probably altered by water. Gusev zone is a complex geological zone. It has probably been undergone volcanic, meteorit impact and watering process.

Rodolfo

[djellison]

I thought Olivine couldnt last long in water - hence the dissapointment when the rocks out on the plains back in the early days contained plenty of it - bog standard olivine rich basalts.

I was at the Natural History Museum again yesterday, going round photographing all the minerals samples - there's THOUSANDS

Doug

[Guest_BruceMoomaw_*]

The olivine puzzle is starting to be resolved in a way that makes consistent sense -- but that's something I can't talk about until my short item on Mars Express comes out on the "Astronomy" website, hopefully tomorrow. Heh heh heh...

[tty]

WOW..... look at the thin ridge like feature running in front of Spirit in this navcam sequence.

http://qt.exploratorium.edu/mars/spirit/na...2EP0715L0M1.JPG

http://qt.exploratorium.edu/mars/spirit/na...2EP0715L0M1.JPG

I've never seen anything like that at Spirits site before.

It looks very much like a fissure filling that is harder than the surrounding matrix and therefore has weathered less.

tty

[aldo12xu]

What about these rounded clasts in this outcrop from sol 688?


http://marswatch.astro.cornell.edu/pancam_..._1_True_RAD.jpg

Are we looking at impact breccia? Are those really clasts or could alteration and weathering give the outcrop that sort of appearance?