[X] My Assistant

[dot.dk]

Looks like the new bright stuff churned up by Spirit has gotten the attention from the PI on Mount Itacha

Spirit Front Hazcam

Latest Steve update

So what is this new stuff (which we have named Arad)? The same kind of salt? Something different? Similar concentration or even saltier? It was too tempting a target to pass up, and we're going to spend the weekend doing IDD work on it before moving on.

[CosmicRocker]

"Mars - "Dramatically different from anything we've seen anywhere else!""

It's similar in appearance to Paso Robles, but even brighter and possibly 'fluffier.' I look forward to some MIs and a Moessbauer. Might this area contain even higher concentrations of sulfates, as SS suggested? Iron geochemistry has always fascinated me, and the confirmation that "Most of it (Paso Robles) was ferric sulfate salts," really intrigues me.

It is worth a pause on the run to Home Plate.

[Bill Harris]

"...and not stop for anything unless something extraordinary popped up. Then something extraordinary popped up."

Heh heh heh. Knew it would happen.

I saw that FHazcam yesterday and _knew_ that they ought to stop. It may well be residual salts left over from weathering. Look ahead and there is a ledge of bedrock near the path; there may be a connection.

Eh. Don't have a closer image of that bedrock, but here is a possible-route image I did a couple of days ago. The ledge is near the end of the blue path-line on the left. Seems to me that we are near that spot.

Always something wondrous here, no?

--Bill

[slinted]

We'll have to make this new one Paso Robles 3, since Paso Robles 2 was used to name a particular patch of bright soil dug up by Spirit from sol 424 to 431.
Here's what that trench looked like back on Sol 431 (the mark slightly below center is the target Paso Light, described below).

The JGR Planets preprint APXS paper(11 MB file) by Gellert et al. gives some great details about the findings at some of the previous bright soil targets.

The largest concentration variations are revealed by two nearby soil locations in the Columbia Hills: Paso Robles and Paso Light (Figure 20). These disturbed soil targets had a S content that was nearly 5 times higher compared to the ‘Gusev Soil’ (sol 14); however, most elements were lower in Paso Robles except for P, Ca, Fe and Br (Figure 20). The concentrations of S in the Paso Robles soils are up to 12.7 wt.-%, which are even higher than those of the ‘dirty’ evaporite outcrops in Meridiani Planum [Rieder et al., 2004]. The high S content of Paso Light is accompanied by a high Fe content (Figure 21), consistent with the identification of ferric sulfate as the main iron-bearing mineral by the MB spectrometer [Morris et al., this issue].

The highest P abundance of 2.4 wt.-% was observed in Paso Robles disturbed soil, in contrast to the average concentration of about 0.36 wt.-% for undisturbed soil  surfaces. Similarly, the Br concentrations of about 500 ppm of the two Paso Robles soil measurements are remarkably high. Based on these high S, P, and Br concentrations, these elements appear to have been transported by water to this area and then concentrated by evaporative processes (see Ming et al., this issue, for more details).

[Guest_Oersted_*]

Maybe Home Plate will turn out to be a deposit of these salts as well... - Just an idea.

[Bill Harris]

Thanks, Slinted, for that reference. I recall it now.

What I suspect has happened is that mineralized groundwater (picked up sulfate and metals, etc from weathering rocks) was transported through a pervious layer over an impervious layer, reached the outcrop, evaporated and concentrated the salts in the soil. This implies liquid water, and some heatflow from below and/or freezing point depression, but it's not too much of a stretch.

I related items, I've noted that there is this beautiful purple material below the
"A-Horizon" that gets exposed by the wheel churn. I wonder what that is?

--Bill

[Bob Shaw]

Bill:

Any ancient brines at Gusev (or anywhere else on Mars) could have been very salty indeed, which would make 'normal' water seem like quite a different substance. I've often wondered what role brines may have played, for example, in the formation of rampart craters - the way the lobate flow so often stops *dead* at a specific distance from the crater might be as much about salty water freezing/boiling off as about the ballistics and other mechanical processes of crater formation.

As for Home Plate as an exposed remnant of an ancient salt-water environment - an interesting thought, not least because the darn thing may well be exposed top to bottom and as such could provide us with some real stratigraphy... ...whatever it is!

Bob Shaw

[ljk4-1]

Maybe Home Plate will turn out to be a deposit of these salts as well... - Just an idea.

About that white stuff under the Martian dirt:

There was a theory in the early 20th Century that the Moon was a ball of ice covered in a thin layer of regolith.

I'm just sayin'....

[atomoid]

Im suspecting there to be an extensive layer at some depth of really salty stuff, whether it be long dessicated by now, or still protected and moist or icy (or replenished in some unlikely manner). Gusev, a landlocked sea for an unspecified period of time, could have accumulated quite a salt playa that has been buried under much dusty stuff blown in from surrounding areas over the billions of years or perhaps overlain by catastrophic sediments from more recent epochs.

Homeplate, if it is the exhumed salt-filled cup of a buried crater from that watery era, should produce a very noticeable wind tail of blown salts as it decomposes, but we dont see that.

Could these salts be locked up very securely somehow? otheriwsse it suggests that it is composed of something quite different.

[nprev]

Hmm. Does the fact that these salt deposits exist in such discrete 'pockets' imply that they were formed by relatively brief moist events, then preserved by a prolonged dry period? Additional moist periods would presumably diffuse these deposits over time.

I'm having a hard time understanding exactly how this material has remained pristine just under the surface, given the probable rate of eolian soil transport in Gusev due to dust devils. Curiouser and curiouser....

[Shaka]

Hmm. Does the fact that these salt deposits exist in such discrete 'pockets' imply that they were formed by relatively brief moist events, then preserved by a prolonged dry period? Additional moist periods would presumably diffuse these deposits over time.

I'm having a hard time understanding exactly how this material has remained pristine just under the surface, given the probable rate of eolian soil transport in Gusev due to dust devils. Curiouser and curiouser....

But then again these pockets seem to be reservoirs of fines - hence the wheels 'churning' the salts up. So the pockets may be localities of net 'soil' deposition - more eolian cul-de-sacs - in contrast to the hard, pebble-strewn areas of net erosion. Also, in applying the time factor to understand what we see on Mars, we may need a vastly greater scale unit than what we are used to on earth. It's almost scary. Can we really guess how long those salts have lain undisturbed?

[CosmicRocker]

Do we really know that there are "pockets" of this stuff? We've seen this in several areas where Spirit's wheels churned the stuff up from below, but only because the rover's forward progress was difficult and the wheels dug into those areas. I doubt they would take the time to do it, but I'd like to see some exploratory trenching in several areas in order to map out the extent of this material.

I'm not suggesting the material is laterally extensive, but we really don't know that it isn't.

[CosmicRocker]

Every once in a while the raw images come down with reasonably similar exposures (I guess that's the reason.) and you can make a decently colored composite that doesn't suffer too much from the "blue plague." Here is a false color pancam of the churned area. There are five or six differently colored materials here. One of them is a violet or rose-colored material. Is this the purple stuff you mentioned, Bill?

Raw images courtesy of NASA/JPL-Caltech. Color composite courtesy of MidnightMarsBrowser.

Attached thumbnail(s)

 

[alan]

I used a different combination of filters to bring out the color differences in the bright material

[CosmicRocker]

You sure did! That's awesome, alan. There are even more differently colored materials here than I imagined. I'm almost tempted to comment on the composition of some of this stuff, but I know better. (Biting my tongue) Arad is a veritable rainbow of colors, though. I know these are still false color at this point, but the relative differences are relatively real, are they not? I'll go out on a limb here, and suggest this site has the broadest range of hues that we've yet seen in any Martian materials. Are there any other candidates?

I wish there would be more time for a detailed and systematic study of this site.

edit: P.S. I think this is a Pandora's box.

[nprev]

Could be that the different tints are due to various states of mixture between the white stuff & the "normal" soil...could also be some other sorts of transition metal compounds, possibly another result of water interaction...odd.

BTW, that rock on the right edge of the trench looks a bit shiny & metallic in this view. Is this an artifact of the color processing, or is this another meteorite candidate?

[CosmicRocker]

Oh, no doubt there is some mixing going on with some of the tints. But there are clearly several end-members contributing to the mix.

[Nix]

some stereo on the trenching;


color stereo @ 50% and anaglyph, Spirit, sol 721

Looks even more Spectacular then PR1 and 2 I think, hmm...back to that 'old' data...

Nico

[Bill Harris]

This is quite a site. I think that some of the range of colors we see are from the mixing of differing tints, but also from differently colored layers in the deposit. Or so it seems to me. The mechanical properties of the material are unique-- I'd say "fluffy", too, but just for lack of a proper word. It has a fluidity to it, look at how it has flowed around that vesicular rock on the right. Not to imply water-wet.

On future Rovers we need a "trenching tool", a narrow blade that can be dropped down 0-1-2-4-6" and locked down; the digging is accomplished by the Rover driving. The wheel-trenching is adequate, but fro fine structure it has the subtlety of a sledge hammer.

The blue color is an intense indigo. NOT subtle. Let me dig thru my archives, but here is a recent example from the Comanche area. This is apples/oranges since mine is an L257 and yours is an L456. The other examples I'm thinking of are from "around Larry's Leap" in the Hills.

--Bill

[nprev]

Spectacular, Nix!!!!


The sharp delineation of the white material is incredible.

This may or may not be germaine to the topic, but about thirty years ago after Viking I made a Mars jar for a science fair project and mixed the "soil" up based on the Viking 1 composition analysis. I used fine-powder sulfur and magnesium (I think) oxides in addition to various iron oxides for the soil mix, sucked out the air with a vacuum pump, replaced it with basically pure CO2, and tried to grow a couple of succulents (also had a nice red lichenated rock in there...looked awesome!)

The point of that story was that no matter how thoroughly I mixed the soil, the Mg oxide always seemed to settle out in thin, uniform white layers just under the surface; the entire soil depth was about four inches. At the time, I accepted this as a consequence of the purity of lab-stock compounds and my own amateurish mixing...now I wonder if maybe the model soil was a LOT more accurate than I thought, at least with respect to Gusev...

[nprev]

This is quite a site.  I think that some of the range of colors we see are from the mixing of differing tints, but also from differently colored layers in the deposit.  Or so it seems to me.  The mechanical properties of the material are unique-- I'd say "fluffy", too, but just for lack of a proper word.  It has a fluidity to it, look at how it has flowed around that vesicular rock on the right.  Not to imply water-wet.

On future Rovers we need a "trenching tool", a narrow blade that can be dropped down 0-1-2-4-6" and locked down; the digging is accomplished by the Rover driving.  The wheel-trenching is adequate, but fro fine structure it has the subtlety of a sledge hammer.

The blue color is an intense indigo.  NOT subtle.  Let me dig thru my archives, but here is a recent example from the Comanche area.   This is apples/oranges since mine is an L257 and yours is an L456.    The other examples I'm thinking of are from "around Larry's Leap" in the Hills.

--Bill

Hmm. Cupric oxide, perhaps? That's a REALLY deep blue...and it's also a common precipitate/leach product in mine tailings.

[edstrick]

I grabbed Alan's color version, did a judicious contrast stretch on the bright end (photoshop curves) and an edge sharpening on the brightness. Brings out quite a bit of detail.

There was a salt-patch on the drive from Bonneville to the spur, about 2/3 or 3/4 of the drive, more in the vicinity of "pot of gold" rock, as well as the big patch found later. Similar enhancements on all of them show quite a variety of color differences within the different high reflectance materials, but I can't easily find my old files, buried on non-connected hard drives and over 100 "misc' CD's.

Attached thumbnail(s)

 

[helvick]

Am I right in thinking that we seem to have a pretty well delineated and fairly thin layer of white stuff here, not just a layer of typical Gusev surface material overlaid on a deep bed of whatever this white stuff is?

[edstrick]

I think so.. it's spotty in distribution, not at all clear why.. Here it's pretty clearly in a drift of "fines" on rubbly regolith, not in the fines part of the rubble itself. This deposit must either be an aeolian layer, or salts deposited up into the fines by groundwater, which seems to have not cemented it. A really big question in that model is how is it loose and totally crumbly, not cemented.

I too have continually wished for a trenching tool on these rovers, as I commented some months back. Scuffing works, but it almost totally trashes any interpretible stratigraphy.

[sattrackpro]

I’m really enjoying watching this odyssey here... so much fun! I’m most thankful for this site, and everyone’s great work.

But, looks like next week, after working these ‘bright spots’ over real good with the Moessbauer, it’ll be very interesting to see what kind of dune-dodgin’ Spirit will have to perform to get ‘round the horn.’

It may be the rocks ahead (by the third dune down the road) could make for difficult passage. Does anyone think ‘a long way around’ could be necessary? There’s also what looks like a large fourth dune... it gets interesting’r and interesting’r!

Here’s a sloppy drawing of a couple of ‘maybe detours’...

[Guest_Oersted_*]

Possibly out on a limb here, but maybe Home Plate is the source of these thin layers of white material, perhaps salts, that we see just under the surface in the valley.

There's no distinct tail of white deposits downwind from Home Plate on the surface. This could be because such deposits are blanketed with darker sands from time to time during dust storms.

So, Home Plate could be the source of the white material to the surrounding lower areas. Home Plate itself is higher up, and therefore does not get covered in darker windblown deposits, which rather collect in the eolian cul-de-sacs.

Maybe Home Plate protrudes from the valley floor because it is made of a harder material than the surrounding areas. Would this fit together with Home Plate being white due to salts?

[Guest_RGClark_*]

I grabbed Alan's color version, did a judicious contrast stretch on the bright end (photoshop curves) and an edge sharpening on the brightness.  Brings out quite a bit of detail.

There was a salt-patch on the drive from Bonneville to the spur, about 2/3 or 3/4 of the drive, more in the vicinity of "pot of gold" rock, as well as the big patch found later.  Similar enhancements on all of them show quite a variety of color differences within the different high reflectance materials, but I can't easily find my old files, buried on non-connected hard drives and over 100 "misc' CD's.

Great image. Does the bluish rock near center/right look metallic to you?
It has the appearance of an iron-nickel meteorite.


- Bob Clark

[Bob Shaw]

Great image. Does the bluish rock near center/right look metallic to you?
It has the appearance of an iron-nickel meteorite.
    -  Bob Clark

Bob:

I see a vesicular basalt - it lacks the 'finger sculptured' quality of such a meteorite, nor is there any sign of a fusion crust, should it be a stoney-iron.

Presumably, however, deflation of the surface in areas subjected to regular wind patterns would tend to concentrate meteorites as the loess-like materilas get removed. For my money, as well as a backhoe, I want a magnet stuck on!

Bob Shaw

[mhoward]

Just because it's pretty:

[alan]

false color image of the other side

The reddish clump reminds me of material seen by opportunity at purgatory

[slinted]

Another color shot of Arad in full filter came down today:

as well as some MIs
This stuff (which is looking very similar to the previous Paso Robles material) has got to be my favorite material we've seen from either rover, from a purely colorific standpoint.

[CosmicRocker]

It's just gorgeous, isn't it? I don't remember previous sightings being so colorful, but perhaps I have forgotten, or we didn't look as closely, earlier. Can anyone dig up some old images, or newly processed, old images?

I've been trying to imagine a sequence from the physical evidence here, and one which makes sense chemically from the color evidence. It's probably crazy to try, though. This soil is so churned up. I know we can't fully trust the colors, but the typical problems with the over-exposures on the blue end seem to be minor in these recent sets. It sometimes appears that these "full filter sets" are a bit better behaved.

I'm going to go _way_ out on a limb here and suggest that the yellow stuff is reminiscent of native sulfur, the shades of gray and exaggerated blue suggest reduced iron species in the particles, and the "rusty" orange-brown stuff resembles rock fragments containing oxidized iron ions. The white stuff has already been identified by SS as largely sulfates of iron.

Oh great. Apparently ferric sulfate can also be yellow. Nevermind...back to the drawingboard... Thank goodness someone will get the lowdown from the Moessbauer and APXS eventually.

[Bill Harris]

It _is_ hard to figure out exactly what is going on here. But I think that your drawing board is still good, think of sulfates in various states of oxidation-reduction with different metals balancing out the SO4's. I've seen/heard of that happening in minespoil piles with pyrite oxidizing like mad til it sucks up all the O2, then it switches gears. Sulfates are important since they serve as an energy source for a class of microbes, the thiobacillus group. Ya gotta have food for bugs in the desert...

Still digging in my archives for colorful images. I _do_ need some sort of indexing system.

--Bill

[sattrackpro]

It _is_ hard to figure out exactly what is going on here.

Sure is... I'm not much of a chemist, or geologist, just an avid rock-hound that's been tinkering at the hobby for about 50 years... I've seen stuff like this right here on good old terra firma quite often, and your comment on minespoil nails exactly where I've seen stuff like this.

Typical content is just SiO2, and CaCO3, but the ‘pretty stuff’ is in metal oxides, primarily iron, aluminum, magnesium and lead - in that order of prominence. The zeolites and feldspars being what I’m after (crystalline forms of) - and this mars dig looks akin to Analcime - often a multicolored zeolite, but usually white. It's usually aluminum based, but with lead it goes multi-color. Wish they would publish more on what elements the spectrographic work shows...

[Mongo]

Wish they would publish more on what elements the spectrographic work shows... 

slinted gave a link to a paper that goes into great detail on the results of 93 different APXS integrations, on the first page of this thread.

Examples of several results from that paper (numbers in parenthesis are two-sigma errors):

sol 14 Gusev soil (integration time 13.5 hours)

Na2O: 2.8 % (0.3 %)
MgO: 8.34 % (0.12 %)
Al2O3: 9.89 % (0.14 %)
SiO2: 46.3 % (0.5 %)
P2O5: 0.87 % (0.08 %)
SO3: 6.61 % (0.08 %)
Cl: 0.78 % (0.02 %)
K2O: 0.48 % (0.06 %)
CaO: 6.36 % (0.05 %)
TiO2: 0.86 % (0.07 %)
Cr2O3: 0.31 % (0.03 %)
MnO: 0.33 % (0.01 %)
FeO: 16.0 % (0.11 %)
Ni: 556 ppm (51 ppm)
Zn: 293 ppm (18 ppm)
Br: 31 ppm (17 ppm)

sol 172 Pot of Gold RAT (integration time 5.0 hours)

Na2O: 3.0 % (0.2 %)
MgO: 9.91 % (0.13 %)
Al2O3: 10.32 % (0.13 %)
SiO2: 42.9 % (1.4 %)
P2O5: 1.08 % (0.08 %)
SO3: 7.96 % (0.10 %)
Cl: 0.57 % (0.01 %)
K2O: 0.20 % (0.06 %)
CaO: 5.86 % (0.05 %)
TiO2: 0.77 % (0.07 %)
Cr2O3: 0.27 % (0.03 %)
MnO: 0.24 % (0.01 %)
FeO: 16.7 % (0.12 %)
Ni: 894 ppm (52 ppm)
Zn: 112 ppm (13 ppm)
Br: 77 ppm (17 ppm)

sol 401 PasoRobles disturbed soil (integration time 2.7 hours):

Na2O: 1.6 % (0.2 %)
MgO: 5.53 % (0.09 %)
Al2O3: 4.13 % (0.07 %)
SiO2: 21.8 % (0.3 %)
P2O5: 5.61 % (0.14 %)
SO3: 31.7 % (0.30 %)
Cl: 0.55 % (0.02 %)
K2O: 0.19 % (0.06 %)
CaO: 6.84 % (0.06 %)
TiO2: 0.62 % (0.07 %)
Cr2O3: 0.04 % (0.03 %)
MnO: 0.25 % (0.01 %)
FeO: 21.0 % (0.12 %)
Ni: 109 ppm (49 ppm)
Zn: 98 ppm (18 ppm)
Br: 494 ppm (26 ppm)

Bill

[dilo]

Hey, Spirit is working on this stuff also after "local Sunset"!
(Sol 723, enhanced brightness, crossed eyes)

Attached thumbnail(s)

 

[JonClarke]

This stuff (which is looking very similar to the previous Paso Robles material) has got to be my favorite material we've seen from either rover, from a purely colorific standpoint.

Jarosite, which is yellow, has to be a strong candiate. Alunite and Ca-Mg-NA sulphates are all white. Given the amount of jarsoite that is supposed to exist on Mars it is nice to actually see some at last.

Jon

[Bill Harris]

That's right: color. Mineralogy 101. Duh.

--Bill

[CosmicRocker]

Hey, Spirit is working on this stuff also after "local Sunset"! 
(Sol 723, enhanced brightness, crossed eyes)

Hehe , she is quite a workaholic, isn't she?

The appearances of such stuff are among the most interesting observations Spirit has returned from Gusev Crater.

[Nix]

true color is up;

http://marswatch.astro.cornell.edu/pancam_...true_color.html

Nico

[jaredGalen]

Wow, Spirit does look really dusty in this one;
http://marswatch.astro.cornell.edu/pancam_..._1_True_RAD.jpg

[dot.dk]

Wow, Spirit does look really dusty in this one;
http://marswatch.astro.cornell.edu/pancam_..._1_True_RAD.jpg

I have noticed how the solar panels have lost some of its great dark color in the last few months...

I think being down here in the basin deposits more dust than if you are on a hill

[sattrackpro]

slinted gave a link to a paper that goes into great detail on the results of 93 different APXS integrations, on the first page of this thread.
- - -
Bill

Thanks very much, Bill - that is a great piece - very informative! There are also a number of other pdf's in that pip directory (see just by trimming the trailing file) that are most interesting.

[Jeff7]

I have noticed how the solar panels have lost some of its great dark color in the last few months...

I think being down here in the basin deposits more dust than if you are on a hill 

Being near El Dorado probably doesn't help any - looks like a prime spot for dust deposition.

[Toma B]

Wow, Spirit does look really dusty in this one;
http://marswatch.astro.cornell.edu/pancam_..._1_True_RAD.jpg

WOW that's awfully dirty!?! When did that hapen???
Get out of there Spirit, fast!!!

[dvandorn]

Wow, Spirit does look really dusty in this one;
http://marswatch.astro.cornell.edu/pancam_..._1_True_RAD.jpg

Oh... hey... there is orange soil here!

Oh, all right -- on Mars, there is orange soil everywhere. But some of the overturned dirt in this particularly interesting set of tracks is really orange-red in these true-color images. Moreso than the regular reddish ground soil.

-the other Doug

[Bob Shaw]

Oh... hey... there is orange soil here!

Oh, all right -- on Mars, there is orange soil everywhere.  But some of the overturned dirt in this particularly interesting set of tracks is really orange-red in these true-color images.  Moreso than the regular reddish ground soil.

-the other Doug

other Doug:

They shoulda called it 'Shorty'!

Bob Shaw

[slinted]

This JPL photojournal writeup confirms findings of iron sulfates in Arad, much like Paso Robles.

[CosmicRocker]

Yeah, Dan. I also noticed that they posted the same infomation at the MER site. http://marsrovers.jpl.nasa.gov/gallery/pre.../20060120a.html

"These images from Spirit's panoramic camera (Pancam) show some of the most colorful deposits yet photographed on the surface of Mars."

I was happy to see them verify that this site was, as I previously suggested in post #32, "so colorful." I still like the false-colored versions better, though. I am also happy to learn that this is essentially another Paso Robles. We didn't need another Martian Mystery.

Doug^2: I agree. There is Orange, and then, there is Orange.


On a completely different and OT note, has anyone else posted a link to the Steve Squyres' Podcasts elsewhere in the forum? I stumbled upon them earlier today.
http://marsrovers.jpl.nasa.gov/gallery/podcast/ They are seriously worth listening to. ...the latest news, as far as I know...amazing stuff...

Am I the last person here to discover this?

[Bill Harris]

No, next to the last person. It's buried in Multimedia/Podcasts, and there is nothing to suggest that there are text transcripts. Although MP3 is doable, some of us find 8mB downloads a bit heavy.

--Bill

[sattrackpro]

...and there is nothing to suggest that there are text transcripts.

But there are transcript links on the page cited...

Here links... Part 1 and Part 2

Most interesting - particularly about water being mostly laced with sulfuric acid...

[stevo]

This comment also

"Well, with Opportunity, we'd like to see even deeper into the crust, we'd like to find an even bigger hole to climb down into, or we'd like to find a place where we can climb up into higher layers. Basically, what we've got now is we've got about 20 to 25 feet of this stack of rocks that we have examined in detail. I'd like to double that, triple that, quadruple that. And in order to do that, you have to go other places."

Hmmm. Opportunity, bigger hole ...

[Bill Harris]

I have the text transcripts saved. What I meant was in the Podcast link on the Multimedia page there is nothing to suggest that there is nothing to suggest a transcript in the Podcast link. Unless you're interested in Podcasts you'll not go down 2-3 layers.

--Bill

[slinted]

The latest update from Steve Squyres revealed some of what Spirit found at Arad:

At Gusev, Arad turned out to be worth the stop.  It's extraordinarily high in ferric sulfate salts, and it now holds the record for the saltiest place ever discovered on Mars. Interestingly, though, it doesn't seem to have the phosphates that Paso Robles did. We're still pondering on this one.

Breaking the 'saltiest soil' record couldn't have been easy, the recent JGR APXS paper identified Paso Robles as being 49% by weight ferric sulfates.

It would seem that the phosphates are going to pose a much bigger challenge to our understanding. Paso Robles had more sulfates and more P than any other place yet sampled by Spirit. It didn't seem like it would be too far of a stretch to think that both components had been transported together. But if Arad shows only the sulfates, and none of the phosphates, then the theories of transport get a whole lot more complicated.

Also still lingering is the issue of concentration. Why are these patches so specially localized? Why haven't these areas been mixed in? Spirit has now seen two very dense patches of salt that don't appear to have been stirred into the surrounding soil.

[Bill Harris]

Also still lingering is the issue of concentration. Why are these patches so specially localized?

Applying a terrestrial analog: mineralized ground water, traveling along a bedding plane or perched aquifer, hits the outcrop, the water evaporates along the outcrop leaving a high concentration of Fe+ and SO4- and whatever other anions/cations were dissolved.

Either that, or think Hydrothermal.

See the "approach to the crest of Mitcheltree Ridge" image in the "Speculations" thread.

--Bill

[CosmicRocker]

As Bill said, such things can easily be localized by a number of conditions, but I'll ask again; how do we really know they are "localized?" We've only seen them in some localized areas, but that may only be because the wheels were forced to dig into a few localized areas.

The partitioning of phosphorous does seem to be a localized phenomenon, but I think it might be explained by selective leaching of elements from a very heterogenous pile of rock, emplaced by impacts and volcanic events on the young planet.

I think that planetology has much to learn about the early history of planetary formation from missions like this. Most, if not all, of the rocks from this period, no longer exist on our planet.