New Bright Stuff, Paso Robles 2 Options

[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.