I was interested to see that they used 15 different spectral bands to make these tentative identifications. Perhaps they could apply this analysis to the blue areas seen in some rocks at the Pathfinder site. I wrote about these in the sci.astro post copied below.
I wrote about this to the Antarctica researcher David Wynn-Williams, who died in a tragic accident recently. He responded that he had seen iron-rich rocks with blue coloration on the wind-blasted side in Antarctica. But he attributed it to reduced iron, nonbiologically produced. However, it is known some species of microorganisms reduce iron as a means of gaining energy.
It would be interesting to see if the blue areas seen on the Pathfinder rocks match the spectra of these blue areas on the Antarctica rocks regardless of their origin.

Bob Clark

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From: Robert Clark (rgregoryclark@yahoo.com)
Subject: "Blue Mars" - further evidence of cyanobacteria on Mars?
Newsgroups: sci.astro, sci.astro.seti, alt.sci.planetary, sci.bio.misc
Date: 2002-01-02 13:03:03 PST

In a prior post to sci.astro I raised the possibility that dark spots
seen in the Malin/Edgett gullies on Mars might be indications of
cyanobacteria:

From: Robert Clark (rgclark@my-deja.com)
Subject: Dark spots in Mars gullies - evidence of cyanobacteria?
Newsgroups: sci.astro, sci.astro.seti, alt.sci.planetary, sci.bio.misc
Date: 2001-11-29 14:05:07 PST
http://groups.google.com/groups?th=b4c2374dcdf153f6

Members of the Pathfinder imaging team noticed a bluish tint on
some surfaces of rocks at the Pathfinder site:

Photographs show red, white and blue rocks on Mars
http://www.floridatoday.com/space/explore/stories/1997b/072997c.htm
"In panorama photos taken by Pathfinder of its landing site, there
is a striking two-color appearance on dozens of rocks, Smith
said.
"You divide the scene into two parts - the red part and the blue
part,' he said. 'There is a very clear difference between the red
side and the blue side.'
"Smith said that the blue side is on the east side of the rocks,
suggesting that the sometime-ferocious wind storms on Mars
may have scoured off a layer, uncovering the color. The west
side of the rocks, protected from the wind, are red, probably from
layers of Martian soil, he said.
"The strong wind comes through and it could have sandblasted
the one side of these rocks," he said. "

This is discussed further in a report given at the 31st LPSC:

Blue Mars
http://www.lpi.usra.edu/meetings/lpsc2000/pdf/1938.pdf

Note that the bluish tint on the wind-blown side would be
consistent with endolithic "blue-green algae", that is,
cyanobacteria, known to exist under surface on rocks in desert
environments and in Antarctica:

Search For Martian Life Will Need Good Vibrations
"University of Bradford PhD student Emma Newton is playing a
part in helping NASA's planned exploration of Mars which many
people hope will lead to discovering life on the planet.
"Emma works in the Department of Chemical and Forensic
Sciences studying lichens and cyanobacteria (also known as
blue-green algae) for the purpose of understanding the survival
strategies adopted by life in the Antarctic.
"Emma said:'whereas some microbial communities live on the
rock surface and use sunscreen pigments to protect
themselves, others can live within the rocks themselves. These
are known as endolithic and it can be pretty difficult to get a look
at them. Raman spectroscopy makes it possible for us to
examine these communities without damaging either the
microbes or their habitat."
http://www.spacedaily.com/news/mars-life-01i.html

The winds on Mars could have removed the dust covering to
reveal the endolithic microbial communities underneath.

Also in an earlier post to sci.astro copied below I discuss the fact
that Viking imaging scientists also observed blue-green tints on
surfaces at the Viking sites.

Gil Levin used this fact to suggest there could be lichen on Mars:

Color and Feature Changes at Mars Viking Lander Site,
Journal of Theoretical Biology, (1978) 75, 381-390.
http://www.biospherics.com/mars/color/color.htm

Lichen can be communities of either fungi and algae or fungi
and cyanobacteria, "blue-green algae". I should note though that
the scientist I quote in the sci.astro post Edwin Strickland
disagrees with Gil Levin's suggestion that such colors could be
indications of lichen on Mars. Strickland noted that searches for
chlorophyll were negative.
However, Barry DiGregorio in his book _Mars: the Living Planet_
noted that the spectrographic signature of chlorophyll in lichen
can be obscured.

The report by Strickland can be found at:

Soil Stratiography and Rock Coatings Observed in
Color Enhanced Viking Lander Images,
by Edwin Strickland,
Proceedings of Lunar and Planetary Science 10, Volume 3, pp.
1192-1194 (1979),
http://adsabs.harvard.edu/cgi-bin/bib_query?1979LPI....10.1192S

Bob Clark

__________________________________________________
From: Robert Clark (rgclark@m...)
Subject: Re: Algae on Mars
Newsgroups: alt.sci.planetary, sci.astro, alt.life-mars,
sci.bio.misc
Date: 2000/05/14

The paper cited below by Edwin Strickland, "Soil Stratiography
and Rock Coatings Observed in Color Enhanced Viking Lander
Images",
Proceedings of Lunar and Planetary Science 10, Volume 3, pp.
1192-1194
(1979), is now available on NASA's Astrophysical Data service,
http://adsabs.harvard.edu/abstract_service.html?nosetcookie=1.
Search under Strickland, E. for this article as well as other
articles by Strickland examining the colors of Mars.

*********************************************
Forum: alt.sci.planetary
Subject: Re: Algae on Mars
Date: 01/30/2000
Author: Robert Clark <rgclark@m...>

In article <38932465.6A5A213A@l...>,
"J. Scott Miller" <Scott.Miller@l...> wrote:
> Bruce Sterling Woodcock wrote:
> >
> > Firstly, I already posted the URL, but here it is again:
> >
> > http://www.biospherics.com/mars/spie/spiehtml.htm
> >
> > Secondly, I'm not talking about sand changing from light to dark from
> > orbit. I'm talking about rocks changing from red to green in front of
> > Viking's camera.
> >
> > Bruce
>
> I have seen the Viking imagery and have seen no such changes in the rocks. I
> have just read the page again and all I see is someone grasping at straws,
> pulling in unrelated material to make a case for something that others simply
> don't see, others, I might add, that probably know more about the topic than
> the individual writing the paper you keep providing a link for. In other
> words, someone who knows nothing about what is going on is trying to tell
> those that do that they are blind. The scenario is often posted here in
> sci.astro, and routinely that individual is shown to be incorrect in their
> underlying assumptions. This would seem to be the case again.
>
> --
> J. Scott Miller, Program Coordinator Scott.Miller@l...
> Gheens Science Center and Rauch Planetarium
> http://www.louisville.edu/planetarium
> University of Louisville
>

Barry Digregorio in his book _Mars: the Living Planet_,
http://www.amazon.com/exec/obidos/ASIN/1883319587/marsbugstheelect,
discusses that members of the Viking imaging team also noted
greenish-blue patches on rocks at the Viking landing sites after
Gil Levin brought them to their attention:

"Subtle color variations of the martian surface materails were
enhanced in eight Viking Lander color images processed at the
U.S. Geological survey's Flagstaff, Arizona, Image Processing
Facility ... color artifacts due to Lander cameras are minor and do
not hamper image anlalyis.[See Color Plate 15.] Two tests
demonstrate that colors in the enhanced images represent real
features of the martian scene. Ovelapping images taken with
separate cameras reveal the same relative colors. Two images
of the same scene taken at different times of day show that
colors of sunlit materials do not depend strongly on illumination
... five distinct soil colors have been recognized at the Viking 1
site ... a thin layer of intermediate brightness "green-blue" soil is
present as smooth patches that fill shallow dips and hollows in
the duricrust ... Rocks at the Viking 1, most probably bedrock and
many other loose rocks near the lander, have very light surfaces,
with a green ratio greater thn any other surface material. They
appear bright green in enhanced images ... At the Viking 2 site,
only one color population of rocks appear to be present. Green
colored surfaces are abundant on rocks of all textures."
Edwin Strickland, "Soil Stratiography and Rock Coatings
Observed in Color Enhanced Viking Lander Images",
Proceedings of Lunar and Planetary Science 10, Volume 3, pp.
1192-1194 (1979), as cited on page 184 of _Mars: the Living
Planet_.

However, it appears from subsequent discussions of Levin with
members of the Viking imaging team cited by DiGregorio that
they did not investigate the color changes on rocks noted by
Levin, though they may have investigated color changes in the
soil itself.

Perhaps Mr. Digregorio can provide the NASA reference
numbers for the images that Levin claims show the color
variations with time.

_______________________________________________

"In order for a scientific revolution to occur,
most scientists have to be wrong."
-- Bob Clark
_______________________________________________

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