Home, Sweet Home, Dream becomes Reality Options

[Tman]

I keep thinking in terms of artesian springs.  I've seen a number of them on Earth, and especially those which vent volcanically heated water tend to bear water that's absolutely saturated with minerals.  The "throw" distance from the source of the spring makes an obvious difference in the lithologies of the rock that's deposited by the flowing spring water.

-the other Doug

If it's such a former spring, would you expect any sign of it on Home Plate where the "water" came out.

[RNeuhaus]

If it's such a former spring, would you expect any sign of it on Home Plate where the "water" came out.

In order to probe it (spring), then around the HP must have at least a hole where comes out the hot water. Sure it must be buried due to billions years of sand and dust deposition.

Rodolfo

[Guest_Richard Trigaux_*]

Indeedy!

...

And finally: I know it can't be, but... ...lithographic slate? Anybody seen any Archeopteryx? Answers, on a postcard please, to Mr R Hoaxland...

Bob Shaw

If I see an Archeopteryx, I don't send to him, nobody will believe me after

[Shaka]

Setting aside PM for now (we need to see it closer up), wouldn't we see plentiful evidence right in front of us indicative of a "spring" origin? I mean rounded edges, flow channels etc. (I'm not really familiar with worn remnants of springs)? Can anybody point that sort of thing out, as distinct from eolian erosion forms? Is there any reason to doubt that these layers originally ran continuously across this whole exposure?

[aldo12xu]

I think we're looking at strata that has been tilted through meteorite impact. The stereo images below show the bedding planes to be dipping inward at an apparent angle of at least 20 degrees, best seen in the more erosion resistant layers sticking up above the outcrop in the top right. That implies these rocks were present before the meteorite impact.

The fine laminations are not inconsistant with wind deposition and, in fact, where cross-bedding is visible, it is planar stratified, displaying none of the festoon laminations associated with flowing water. So my guess is that these are wind derived sediments. And that is also what the layering at Burns Hill is interpreted as.

I think that's about all we can say for now until we get some geochemistry data.

Left: http://marsrovers.jpl.nasa.gov/gallery/all...00P2364L7M1.JPG
Right: http://marsrovers.jpl.nasa.gov/gallery/all...00P2364R1M1.JPG

[Nirgal]

Here is a color-stitch of the great Sol 746 navcam-series:





BTW.: is it just me or has anyone else noticed the slightly "blurred" quality of the recent Navcam frames (despite the now more clearer winter sky ... ?) esp. compared to last mars-year's crisp & clear navcam around the same time in the season ?

[ljk4-1]

I think we're looking at strata that has been tilted through meteorite impact.  The stereo images below show the bedding planes to be dipping inward at an apparent angle of at least 20 degrees, best seen in the more erosion resistant layers sticking up above the outcrop in the top right.  That implies these rocks were present before the meteorite impact.

I thought the area Spirit landed in was covered in basalt, indicating volcanic activity.

Of course who is to say it could not be a combination of both impacts and volcanoes?

[imipak]

Now _that's_ what we like to see!

http://qt.exploratorium.edu/mars/spirit/fo...55P1206R0M1.JPG

My uneducated intuition makes me think the lower, thicker layers, which seem to have large grains (small pebbles?) embedded in them, are composed of volcanic ash rather than windblown (or water-washed) fine sediments. Of course intuition is reliably wrong...

Question to the geologists: does rock formed from volcanic ash appear any different (to the instruments on Spirit) if the ash fell onto standing water, or onto dry land? Hmm, and I suppose if we imagine that there are repeated episodes of ash fall and periods under water, it will make a difference if the sediments between the water and the ash are water permeable?

Clearly there's SOMETHING different between the lower, coarse layers and the higher fine layers. What else might it be? (this is a real question, not a rhetorical.)

[aldo12xu]

I thought the area Spirit landed in was covered in basalt, indicating volcanic activity. 

The Columbia Hills are older than the basaltic flows covering most of Gusev Crater.

Some of the rocks within Columbia Hills are interpreted to be clastic (eg. Peace may be a basaltic sandstone) and pyroclastic (eg. Wishtone may be a tuff) in origin. These may represent the basement rocks that were present before the Gusev impact event. With the impact event, these basement rocks were thrown up, tilted and broken up, creating brecciated rocks like Voltaire. All these units were subsequently cut by dikes, represented by basaltic rocks like Backstay and Cherry Bomb.

The plains basalts on which Spirit touched down were emplaced some time later.

Hope that helps

--Aldo--

[Shaka]

Now _that's_ what we like to see!

http://qt.exploratorium.edu/mars/spirit/fo...55P1206R0M1.JPG

My uneducated intuition makes me think the lower, thicker layers, which seem to have large grains (small pebbles?) embedded in them, are composed of volcanic ash rather than windblown (or water-washed) fine sediments. Of course intuition is reliably wrong...

Question to the geologists: does rock formed from volcanic ash appear any different (to the instruments on Spirit) if the ash fell onto standing water, or onto dry land? Hmm, and I suppose if we imagine that there are repeated episodes of ash fall and periods under water, it will make a difference if the sediments between the water and the ash are water permeable?

Clearly there's SOMETHING different between the lower, coarse layers and the higher fine layers. What else might it be? (this is a real question, not a rhetorical.)

Aha! But here it is!
http://qt.exploratorium.edu/mars/spirit/mi...55P2936M2M1.JPG
And what , pray tell, is it?
If it's sandstone, I don't see any grains .
If it's scoria, I don't see any gas spaces .
If threatened with torture, if I don't talk, I would quote a Past Maestro of Home Plate" It's deja vu all over again! It's the kind of fabric Oppy has been sinking her abrasive into all over Meridiani! Smooth-lumpy STUFF!
But a geologist would phrase it more ...esoterically.

[alan]

How about some color?

[imipak]

Aha! But here it is!
http://qt.exploratorium.edu/mars/spirit/mi...55P2936M2M1.JPG
And what , pray tell, is it?
If it's sandstone, I don't see any grains .
If it's scoria, I don't see any gas spaces .

"Well... it's rock, isn't it?" /Arthur Dent

Actually the blueberry-esque concave dimples in the lower, whitish (in that image) material has brought the word 'slots' floating up from some dusty recess of the distant past, 18 months or more ago.

And really the darker, upper material *does* seem (to me) to be made up of sand-grains sized particles. As it happens there's an outside wall made of very soft grey-green sandstone about three feet <-- that way from my monitor that looks very like the farker material. it feels sandy if you rub your thumb over it, and there's a small heap of sand grains that have eroded out of it accumulating in tiny wind traps in the corners of wall and ground. It's a terrible building material - it weathers so fast that old older buildings in the area, there's a characteristic 'gumline' vertical profile - sort of a ' UUUUU ' shape, rotated through 90 degrees - where the mortar holding the wall together has withstood wind erosion more strongly than the building stone itself. Co-incidentally it looks a bit like the harder, then layers standing up proud of the adjacent layers, especially in the coarser-grained , thicker layers.


Anyway... I'm still boggling over the image of Homeplate being flipped over like a pancake by an impact event

[dvandorn]

Aha! But here it is!
http://qt.exploratorium.edu/mars/spirit/mi...55P2936M2M1.JPG
And what , pray tell, is it?
If it's sandstone, I don't see any grains .
If it's scoria, I don't see any gas spaces .
...

I know I'm probably not seeing what I think I'm seeing. But it looks a little like limestone to me.

It's got this flat-smooth-plates look to it that reminds me of limestone emplaced in hot springs.

I'm probably wrong, but it's a lovely image...

-the other Doug

[jamescanvin]

I haven't seen these two Pancam ESF's stitched together here yet.



It will be in full filter colour as soon as the data is down.

CODE

746 p2364.15 26  26  0   0   2   54   pancam_barnhill_2cx1r_L234567Rall

James

[DFinfrock]

I know I'm probably not seeing what I think I'm seeing.  But it looks a little like limestone to me.

It's got this flat-smooth-plates look to it that reminds me of limestone emplaced in hot springs.

I'm probably wrong, but it's a lovely image... 

-the other Doug

Yes, similar to what you see at Mammoth Hot Springs in Yellowstone National Park. But deposits like that don't necessarily require *hot* springs; just a source of water with a high mineral content. I have seen lots of flowstone in caves with a similar look. And those are all cold water deposits.

Now I am not suggesting that there was a cave involved. But cold water with lots of dissolved minerals would evaporate very quickly in the thin Martian atmosphere. And the fine-grained mineral deposits should build up steadily. Any sort of mineral spring, hot or cold, should be able to do the job.

David