Mars Exploration Rover Update - December 23, 2004

What needs to be done to prove the source is biological is to gather enough evidence to falsify the non-biological hypothesis.

The aim of the mission is to gather as much information as possible, regardless of which hypothesis it may eventually support or eliminate.

George

Simple logic, until you eliminate the alternative, the conclusion remains ambiguous.

have a very Merry Christmas, George

A Rock Like None Before, Brushed. "Scientists viewed a rock like none seen before on Mars when NASA's Mars Exploration Rover Spirit brushed the surface and took magnified images of this rock dubbed "Wishstone." The circular area of interest, measuring approximately 5 centimeters (2 inches) in diameter, revealed darker pieces of material randomly distributed within a lighter-colored matrix. The rock has poorly sorted granular material, with grain sizes ranging from fine to coarse and some grains that are very angular in shape. Spirit used its microscopic imager on martian day, or sol, 333 (Dec. 9, 2004) to take the four individual frames that are combined into this mosaic view."

Curious are the dark, smooth inclusions apparent in the rock. These might be similar to the smooth, glassy inclusions seen by Spirit in Humphrey and Mazatzal rocks. Alternatively, they could be examples of, apparent, sedimentary films seen at the Opportunity site:

From: snipped-for-privacy@yahoo.com (Robert Clark) Newsgroups: sci.astro,alt.sci.planetary,sci.geo.geology,sci.geo.mineralogy,sci.bio.misc

Subject: Sedimentary films at Opportunity site. Date: 18 Mar 2004 16:26:04 -0800

Clays perhaps?

Bob Clark

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Hmmm, they do bear a superficial resemblance to "rip-up clasts", but (later). Rip-up clasts are typically thin films of clay/ fine sediment/ occasionally bacterial mats which form on the surface of bulk sediment in both aquatic and sub-aerial circumstances, and which later get "ripped up" by rapidly moving fluid (a whirlwind, dust devil, or underwater debris-laden flow, possibly in a strongly seasonal environment) and incorporated into a new unit of sediment. Because the rip-up clasts have not shared the same transportational history as the rest of the grains in the new sedimentary deposit, they have different characteristics - frequently different grain size and rounding to the host sediment. BUT, such clasts are also typically thin (they tend to be the surface

*film* from the pre-existing sediment, which has become indurated by exposure to changing chemistry at the sediment-fluid interface), and even with a preferred orientation to the (putative) clasts in the cited specimen, one would expect to see some more elongate sections through the (putative) clasts. These are not present. You could do some more sophisticated statistics on the shapes of the grains exposed on the flat surface ground by the RAT, but my (practiced) eyeball would put the grain shape at being "sub-elongated" only. [SIDELINE Thinks - online version of the Rittenhouse comparator or the "Tapeworm"? > mentions it's existence, but online images ... can't find any ; the standard references are

Petrology, Vol.223, pp: 117-119

sphericity.? Journal

Incredible as it sounds, I came up with a sex link while searching for that second link ! ]

Where was I? Yeah - the lack of highly elongate sections to my mind rules out rip-up clasts as a reason for this change of texture. To my eye, it looks like a mesothermal deposit of something like chalcedony (loosely) in vughs in a volcanic or hypabyssal rock. What would loosely be called "agate" on earth, if it were banded. I note that a number of the low-relief, dark regions have [excuse me - new years morning, so time for a fire in the kitchen! Where was I again?] a radiating-arcuate fabric in the surrounding crystalline/ granular material. That is what I'd expect to see in volcanics with filled vugs. Nice picture, interesting structures.

The APXS instrument showed Wishstone to be high in phosphorus:

PIA07191: Spirit View of 'Wishstone' (False Color)

Clay is known to be highly absorptive of phosphorus because of its small grain size:

Reducing phosphorus in aquatic systems using modified clays.

This page discusses the absorption of phosphorus on clays and other sedimentary materials:

13.3 Binding of phosphorus in sediments. However, I've been informed that the APXS, Pancam, and mini-TES do not have sufficient resolution to see if the phosphorus is concentrated in the dark, smooth inclusions. But perhaps the mini-TES could measure them if it were placed closer to the target rock than is usually done.

Bob Clark

Robert Clark wrote:

interest,

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sci.astro,alt.sci.planetary,sci.geo.geology,sci.geo.mineralogy,sci.bio.misc

hills.

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The mini-TES viewport is the same as the Pancam. According to this page the Pancam is 1.3 meters above ground level and its resolution is

0.286 milliradians/pixel:

Pancams: Panoramic Cameras aboard the Mars Exploration Rovers.

That means it should be able to resolve something .286/1000 * 1.3 m = .37 millimeters across. The RATTed area in the image on this page is supposed to be 5 cm across:

A Rock Like None Before, Brushed.

On my monitor when I click on the link for the Browse Image, the magnified view of the RATTed area appears about 10 cm across on my screen and I measure some of larger dark inclusions on my screen as 4 mm across. This means the actual size of the larger inclusions should be about 2 millimeters across. This should be well within the resolving power of the Pancam. For the mini-TES though the resolving power is at best 8 milliradians, which means at 1.3 m it can resolve 8/1000 * 1.3 m = 10.4 mm, too large for the inclusions. Is there any way for the RAT arm to scrape off a portion of a rock and hold it close to the camera?

Bob Clark

Which is not (in itself) incompatible with a number of igneous lithologies either..

I don't think there are any grasping capabilities on the rovers.

Thanks for the analysis. What do you think of the dark material on the right side, inside the rim of the RAT hole in this image of Wishing Well rock, which also is supposed to be high in phosphorus:

It also has a soft appearance as the smooth, dark material in Wishstone rock. What materials other than clay might give this soft appearance?

Bob Clark

Aidan Karley wrote:

sci.astro,alt.sci.planetary,sci.geo.geology,sci.geo.mineralogy,sci.bio.misc

clasts", but (later).

occasionally bacterial mats which form on the

circumstances, and which later get "ripped up" by rapidly

flow, possibly in a strongly seasonal environment)

clasts have not shared the same transportational

they have different characteristics - frequently

surface *film* from the pre-existing sediment,

sediment-fluid interface), and even with a

one would expect to see some more elongate

could do some more sophisticated statistics on

RAT, but my (practiced) eyeball would put the

standard references are

Jour. Sed. Petrology, Vol.223, pp: 117-119

two-dimensional sphericity." Journal

for that second link ! ]

mind rules out rip-up clasts as a reason for

like chalcedony (loosely) in vughs in a volcanic

it were banded. I note that a number of the

for a fire in the kitchen! Where was I

granular material. That is what I'd expect to see

On the right side, parallel to the rim? That looks like the shadow of the rim to me. Compare the orientation of the shadow on the fracture at the rim near the 6:30 position. Otherwise it looks like a fairly normal medium-grained igneous rock. Some signs of primary porosity (vesicles?) at about 8:00. Looks rather leucocratic (but I've no indication of the wavelengths used in the imaging), which would have comparatively high proportions of incompatible elements, which would include phosphorus.

Here is a close-up of part of this dark, soft material in this rock:

dark, soft material

Bob Clar