The dark streaks on Mars became famous because they are widespread features
that are seen to be being currently generated on Mars.
The prevailing view has been they are dry dust flows. However, a report to be
presented to the 2007 Lunar and Planetary Science conference notes that
closely analogous features occur in Antarctica and the authors of the report
note the Antactica streaks are due to freeze-thaw cycles:

SLOPE STREAKS IN THE ANTARCTIC DRY VALLEYS: CHARACTERISTICS, CANDIDATE FORMATION MECHANISMS, AND IMPLICATIONS FOR SLOPE STREAK FORMATION IN THE MARTIAN ENVIRONMENT.
J. W. Head1, D. R. Marchant2, J. L. Dickson1, J. S. Levy1 and G. A. Morgan1.
1Dept. Geol. Sci., Brown Univ., Providence, RI 02912 USA (****@brown.edu), 2Dept. Earth Sci., Boston University, Boston MA 02215 USA (****@bu.edu).
Lunar and Planetary Science XXXVIII (2007) 1935.pdf
http://www.lpi.usra.edu/meetings/lpsc2007/pdf/1935.pdf

This is important because the dark streaks are wide spread near the equator
on Mars. If is true that they are due to freeze-thaw cycling as they are in
Antarctica that would mean that freeze-thaw cycling and therefore liquid water
is widespread near the equator on Mars.
I had earier noted in the post to sci.astro copied below that streaks seen on slopes in Antarctica are similar to the Mars streaks. I surmised the formation of the streaks in Antarctica were due to freeze-thaw cycles.
Since debris flows on slopes in general occur in periglacial regions other than Antarctica due to freeze-thaw cycling there may also be dark streaks as well in such regions, in Europe or North America for example:

Scree slopes.
http://www.tiscali.co.uk/reference/encyclopaedia/hutchinson/m0031374.html

These would then provide more easily accessible and prevalent examples of
terrestrial dark streaks that could provide models for the streaks on Mars and
their possible formation by freeze-thaw cycling.

Bob Clark

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Newsgroups: sci.astro, alt.sci.planetary, alt.astronomy, sci.geo.geology, sci.bio.misc, alt.life-mars
From: rgregorycl...@yahoo.com (Robert Clark)
Date: 10 Dec 2002 23:22:46 -0800
Local: Wed, Dec 11 2002 2:22 am
Subject: Mars dark streaks might be modeled by dark streaks in Antarctica.

Nice discussion on this on Alan Boyles MSNBC site:
Dec. 10, 2002 / 8 p.m. ET
Streakers on Mars: Is there running water on Mars? Presentations at
the American Geophysical Union's meeting this week are revisiting the
debate over what the dark streaks seen on some dusty Martian slopes
represent.
http://www.msnbc.com/news/750150.asp?0dm=W22CT

The streaks might be well modeled by similar streaks seen in
Antarctica:

__________________________________________________________
From: "bobbygc2001" <bobbygc2001@y...>
Date: Sun Jun 30, 2002 7:42 am
Subject: Re: New report supports England/Palermo that the "dark
streaks" are water related.

Images of dark streaks similar to those seen on Mars also appear on
the slopes surrounding Don Juan Pond in Antarctica.

See the image of Don Juan Pond in this report:

DENSE EUTECTIC BRINES ON MARS: THEY COULD BE BOTH COMMON AND
CA-RICH.
Lunar and Planetary Science XXXIII (2002).
http://www.lpi.usra.edu/meetings/lpsc2002/pdf/1240.pdf

The dark streaks in this image also have the digitate (finger-like)
ends common in the Mars streaks.

This report was brought up by Greg Orme on the Mars Red Planet
Roundtable bbs:

http://disc.server.com/discussion.cgi?id=8728&article=38068

See also the images of Don Juan Pond on this page:

SIUC Microbiologists in Antarctica!
http://www.science.siu.edu/microbiology/Antarctica/Antarctic.html

Compare to the dark streaks in Fig 2. on this page due to freeze-
thaw cycling:

Periglacial Form and Process:
"European geologists have long been aware that thick sheets of poorly
sorted angular debris mantled their landscape beyond the limits of
glaciation. The process of fluid motion of sheets of debris down
gentle slopes to form deposits is solifluction. Gelifluction refers
specifically to flow of the active layer (not permafrost) over a
frozen substrate. Meltwater saturation greatly promotes gelifluction
and enables it occur on miniscule gradients."
http://geomorphology.geo.arizona.edu//geos450/LECTURE23/lecture23.html

It would be interesting to find out if these dark streaks have the
property characteristic of the Martian dark streaks of the later
streaks avoiding overflowing earlier streaks.

Bob Clark

--- In cydonia@y..., "bobbygc2001" <bobbygc2001@y...> wrote:

> Dark streaks on slopes have been observed on Mars since the Viking
> missions. The prevailing view is that they are dry slope flows.
> However a new report to be given at this month's AGU meeting will
> present evidence they are water related:
> Title: Evidence for a water phase-transition at low latitudes on
the
> surface of present-day Mars
> Authors: Aharonson,O.;Khatiwala,S.;Schorghofer,N.
> Affiliation: AA(MIT, Bldg 54 Rm 521 77 Massachusetts Ave.,
Cambridge,
> MA 02142 United States; oded@m...), AB(MIT, Bldg 54 Rm 521 77
> Massachusetts Ave., Cambridge, MA 02142 United States;
> spk@o...), AC(MIT, Bldg 54 Rm 521 77 Massachusetts Ave.,
> Cambridge, MA 02142 United States; norbert@s...)
> Journal: American Geophysical Union, Spring Meeting 2002, abstract
> #P31A-11
> Abstract
> The Mars Orbiter Camera on the Mars Global Surveyor spacecraft has
> returned images of numerous dark streaks that are the result of
down-
> slope mass movement occurring under present-day martian climatic
> conditions. We systematically analyzed over 23,000 high-resolution
> images and demonstrate that in addition to forming exclusively in
> regions of low thermal inertia and steep slopes, streaks form only
> where daily peak surface temperatures derived from TES data exceed
> 275 K. The northernmost streaks, which form in the coldest
> environment, form preferentially on warmer south-facing slopes.
> Repeat images of sites with slope streaks show changes only if
> surface temperatures exceeded the melting point of water during the
> time interval between the two images. These correlations suggest
the
> possibility that small amounts of water are transient and undergo
> phase transitions at times of high insolation, providing a trigger
> for the formation of the features.
> http://adsabs.harvard.edu/cgi-bin/bib_query?2002AGUSM.P31A..11A
> ...

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