From: rgregoryclark@yahoo.com (Robert Clark)
Newsgroups: alt.sci.planetary,sci.space.history,sci.astro,sci.astro.amateur
Subject: Re: First color images from 2001 Mars Odyssey?
References: <1017671129.943858@server.gh.wh.uni-dortmund.de> <3CA898A5.A803989F@navix.net> <1017689746.286824@server.gh.wh.uni-dortmund.de> <Gtwpt6.58@spsystems.net> <832ea96d.0204021257.6ee68b47@posting.google.com> <832ea96d.0204060835.74e387c1@posting.google.com>
NNTP-Posting-Host: 147.31.4.2
Message-ID: <832ea96d.0204191027.24a301e2@posting.google.com>

Some reports that make use of color in their analysis of Martian
surface units:

1.) GEOLOGY OF THE REULL VALLIS REGION OF MARS: EVIDENCE FOR
MID-NOACHIAN SHEET FLOODS.
Lunar and Planetary Science XXVIII
Results: COLOR - The Martian surface in and around the
Reull Vallis is nearly monochromatic, as if the surface were
composed of a single reddish material. Almost all color differ-ences
seem to be brighter and darker variants of the same rusty
hue, caused perhaps by changes in slope and solar illumina-tion.
Only the dark wind streaks on the leeward sides of minor
topographic rises (e.g. craters and hills) have significantly
different color. The colors of the streaks are consistent with
mixtures of the reddish material with <20% dark gray material
(visible albedo ~5%). The basement units of the plains sequence
exposed in the valley walls appear to be more yellowish
than other materials, but the difference is not significant."
http://www.lpi.usra.edu/meetings/lpsc97/pdf/1033.PDF

This page has some enhanced color Viking orbiter images from the USGS
Astrogeology section:

Color Images of Mars
http://www.joshuaalmond.com/mars6.html

One of the regions shown is the Reull Vallis region discussed in the
report. The color variations in these images are exagerated, but they
do show color variations do exist. Then quite likely there would be
significant color variations at the 20 m/pixel resolution scale of
Mars Odyssey.

2.) GEOLOGY, COMPOSITION, AGE AND STRATIGRAPHY OF THE POLAR LAYERED
DEPOSITS ON MARS.
First International Conference on Mars Polar Science
http://www.lpi.usra.edu/meetings/polar98/pdf/3009.pdf

3.) Identifying surface changes on Mars from Viking and MGS.
Lunar and Planetary Science XXXIII (2002)
"Variable features are of particular interest
because of the information they yield about both the
geology and meteorology of Mars. Surface changes
due to wind erosion and deposition have been docu-
mented since the Mariner missions [1-6]. Even before
Mariner, Sagan and Pollack [7,8] correctly ascribed the
long term secular changes in Mars' albedo that had
been noted for centuries by telescopic observers to
aeolian transport of sand and dust by saltation and sus-
pension. The systematics of aeolian surface changes
began to be understood with the extensive Viking data
set [9-11]."
"Next Steps: We will continue to explore automated
procedures for change detection; a more sophisticated
approach would track the history of surface brightness
variations to identify those changes that persist over
time. We also look forward to the availability of cali-
bration procedures for MOC blue filter images. Incor-
poration will greatly assist the interpretation of color information
of surface changes and allow us to spot
distracting condensate clouds more easily."
http://www.lpi.usra.edu/meetings/lpsc2002/pdf/1982.pdf

The authors here present the view that the secular and seasonal
albedo changes seen on Mars are only due to variations in the
distributions of dust on Mars. However, one of the regions discussed
here Noctis Labyrinthus is known to present variable low level fogs
than might be an indication of near surface liquid water (Noctis is
both low altitude and low latitude, which means daytime conditions
will frequently be in the range to permit liquid water):

Colorful Water Clouds Over Mars
http://antwrp.gsfc.nasa.gov/apod/ap010417.html

4.)MAPPING UNIQUE SPECTRAL MATERIALS IN VALLES MARINERIS.
Lunar and Planetary Science XXX.
"Within the canyons and surrounding terrains, strong evidence for
variable mafic mineralogy in low albedo units, variable
states of hydration or apparent water content of the soils,
and unusual spectral properties associated with
anomalous color in Viking orbiter images have all been
identified [3,4,5,6]."
"Extensive examination of spectra from the Valles Marineris region
reveals many occurrences of materials that differ in
important but subtle ways from the more common
materials in the scenes. For example, [6] showed that
ISM spectra for a region of anomalous Viking color in
western Candor Chasma exhibited a 1 mm absorption
broadened to shorter wavelengths, consistent with a
surface enriched in crystalline hematite. "
"The ISM data have been co-registered to a Viking
Orbiter MDIM to provide essential context for the
relationship to surface morphology. In addition, red-
green-violet color images were used to provide visible-
color information. In the valley floor of Eos Chasma,
the Viking color data show that much of the floor is
covered by a relatively gray material. Some regions of
the valley floor have a distinct relatively blue color,
while the plateau plains are slightly brighter but with
color that is between gray and blue."
http://www.lpi.usra.edu/meetings/LPSC99/pdf/1484.pdf

The region West Candor Chasm mentioned here is another area presented
on the page "Color Images of Mars",
http://www.joshuaalmond.com/mars6.html, of enhanced color images.
This page describes this enhanced color image in more detail:

West Candor Chasm (Enhanced Color)
http://www.solarviews.com/cap/mars/pia155.htm

It suggests the color variations as due to former lakes and
hydrothermal activity.

Bob Clark

rgregoryclark@yahoo.com (Robert Clark) wrote in message news:<832ea96d.0204060835.74e387c1@posting.google.com>...
> You wouldn't get the impression that Mars is a colorless world from
> this Hubble image either:
>
> Hubble Captures Best View of Mars Ever Obtained From Earth
> http://oposite.stsci.edu/pubinfo/pr/2001/24/
>
> Impossible not to notice that the darker areas have greenish tinge to
> them.
> I found this web site that says this is common from telescope views
> from Earth but attributes it to an optical illusion:
>
> Mars
> "When Mars is viewed through a telescope, it looks like a red and
> orange disk. An observer can easily see white ice caps at the north
> and south poles of Mars. These caps grow and shrink throughout the
> Martian year, just as the polar caps of Earth do. The darker areas of
> Mars's surface may look greenish to the observer, but this is an
> optical illusion caused by the contrast in color between the dark
> patches and brighter areas. Scientists believe that the dark areas are
> regions of relatively unweathered bare rock, while the bright areas
> are regions with deposits of weathered material, especially fine
> dust."
> http://www.cosmiverse.com/reflib/marspage1.htm
>
> Whether this seasonal change is an optical illusion or not is
> something color light imaging from THEMIS could also address.
> I imagine examination of the spectra of this Hubble image also could
> address the question of whether these dark areas really are reflecting
> most strongly in the green part of the spectrum.
>
>
> rgregoryclark@yahoo.com (Robert Clark) wrote in message news:<832ea96d.0204021257.6ee68b47@posting.google.com>...
> > henry@spsystems.net (Henry Spencer) wrote in message news:<Gtwpt6.58@spsystems.net>...
> > > In article <1017689746.286824@server.gh.wh.uni-dortmund.de>,
> > > Holger Isenberg <H.Isenberg@ping.de> wrote:
> > > >> http://mars.jpl.nasa.gov/odyssey/ Pretty color pictures are probably
> > > >> not a high priority...
> > > >
> > > >Can you explain further? We send the first real color camera to Mars orbit
> > > >and its pictures are low priority in relation to 20 m/pixel b&w pictures,
> > > >which already had been taken back in 1972 by Mariner 9?
> > >
> > > They're (probably) low priority because they don't *tell* you anything
> > > new. It was established early that Mars is not a colorful place -- that
> > > is, its color doesn't *vary* much -- and that (conventional) color imaging
> > > thus doesn't add much information compared to B&W images. So tripling the
> > > data volume to bring back color isn't very attractive.
> > >
> > > Note that THEMIS is primarily an IR instrument. The visual part is mostly
> > > just a supplement to the IR imaging.
> >
> > I agree with you that the IR images should have higher priority but I
> > don't agree that color images wouldn't tell you very much. I copied
> > below a post discussing some questions that color imaging could
> > answer. Other questions that would be interesting to answer is what
> > are the colors of the dark streaks seen forming in current times? In
> > the MGS images they look just look black to varying shades of grey.
> > What about the color of the "dalmation spots" that some have claimed
> > to be indicative of life?
> > A region I'm especially interested in is Solis Lacus. This has long
> > been known to be a variable feature on Mars both seasonally and long
> > term. This is interesting because there are several lines of evidence
> > suggesting there could be near surface liquid water in Solis. Are the
> > known albedo changes in Solis accompanied by color changes?
> > This web page by the Association of Lunar & Planetary Observers lists
> > several variable features on Mars that very likely would also be
> > accompanied by color changes:
> >
> > 1998-1999 Aphelic Apparition of Mars: Part 3
> > http://www.astroleague.org/marswatch/Newsletr/imv03i06.html
> >
> > Bob Clark
> >
> > **************************************************************
> > From: Robert Clark (rgregoryclark@yahoo.com)
> > Subject: On the colors of Mars and the mystery of the "Sinton bands".
> > Newsgroups: sci.astro, alt.sci.planetary, sci.astro.seti, sci.bio.misc
> > Date: 2002-02-02 15:19:44 PST
> >
> > The color imager on Mars Odyssey should have about the same resolution
> > as the Viking orbiter, about 20 meters/pixel.
> >
> > A question about some features on Mars is whether some color
> > differences are real or are only apparent in comparison to surrounding
> > terrain.
> >
> > White Rock for example has been claimed to not really be white but
> > only lighter than the surrounding area. Will the color imager be able
> > to determine if it really is white?
> >
> > Another area where the interpretation of its color has been
> > controversial is the Syrtis Major region. It has long been known to
> > present an apparent bluish tint that appears to change seasonally.
> > William Sinton made some spectrographic observations of the area in
> > the 50's that appeared to show it's spectrum matched that of complex
> > organic molecules. This and the seasonal changes led Sinton to
> > originally propose the spectra were due to life. Will Mars Odyssey be
> > able to determine if Syrtis Major really does become blue seasonally?
> > Some of the bands Sinton observed have been explained as actualy due
> > to HDO in Earth's atmosphere. However, the bands at 3.4 microns which
> > are frequently seen in complex hydrocarbons have not been definitively
> > explained. Will the THEMIS infrared imager on Mars Odyssey finally be
> > able to resolve the mystery of the "Sinton bands"?
> >
> > The history of the Sinton bands is told in the second chapter of
> > Barry DiGregorio's book, _Mars: the Living Planet_,
> > http://www.amazon.com/exec/obidos/ASIN/1883319587/marsbugstheelect
> >
> > References on the Sinton bands:
> >
> > Home Page for IRTF Mars Image Gallery
> > Sinton bands in February 1995 IRTF images
> > http://marswatch.astro.cornell.edu/irtf.html
> >
> > 3-4m mm IMAGING SPECTROSCOPY OF MARS.
> > http://www.lpi.usra.edu/meetings/LPSC98/pdf/1658.pdf
> >
> > It's also discussed in the dissertation of David Klassen:
> >
> > Infrared Imaging Spectroscopy of Martian Volatiles
> > by David R. Klassen
> > http://elvis.rowan.edu/~klassen/papers/dissertation/chapter1.htm
> >
> > Bell et.al. have also proposed the aluminum mineral diaspore
> > for the origin of the "Sinton bands":
> >
> > SPECTROSCOPIC EVIDENCE FOR DIASPORE (a-AlOOH) ON MARS.
> > http://www.lpi.usra.edu/meetings/lpsc2000/pdf/1227.pdf
> >
> >
> > Bob Clark
> > ****************************************************