19 Mar 2014 - NASA Orbiter Finds New Gully Channel on Mars

[NASA]

http://solarsystem.nasa.gov/multimedia/gallery/PIA17958_160X120.jpg (http://solarsystem.nasa.gov/news/display.cfm?News_ID=46834)19 Mar 2014 - NASA Orbiter Finds New Gully Channel on Mars
A comparison of images taken by the High Resolution Imaging Science Experiment (HiRISE) camera on NASA's Mars Reconnaissance Orbiter in November 2010 and May 2013 reveal the formation of a new gully channel on a crater-wall slope.


More... (http://solarsystem.nasa.gov/news/display.cfm?News_ID=46834)

[seeker/reader]

Interesting stuff in the article details below. So are they implying that CO2 gas freezes into dry ice and causes frost wedging to create those gullys, in 2.5 years time? That's gotta be the grandest scale of frost wedging ever.:eek:

Here on Earth water frost wedging occurs on a much smaller scale, not creating massive gullys in years but rather turning big rocks into smaller rocks which takes decades.

But I guess on Mars they are trying to push the "there is no water" meme so they are leaning to CO2 to cause the weathering instead. Freeky stuff if true.


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http://solarsystem.nasa.gov/images/PIA17958_720.jpg

A comparison of images taken by the High Resolution Imaging Science Experiment (HiRISE) camera on NASA's Mars Reconnaissance Orbiter in November 2010 and May 2013 reveal the formation of a new gully channel on a crater-wall slope in the southern highlands of Mars.

These before-and-after images are available online at http://www.jpl.nasa.gov/spaceimages/details.php?id=PIA17958.

Gully or ravine landforms are common on Mars, particularly in the southern highlands. This pair of images shows that material flowing down from an alcove at the head of a gully broke out of an older route and eroded a new channel. The dates of the images are more than a full Martian year apart, so the observations did not pin down the Martian season of the activity at this site. Before-and-after HiRISE pairs of similar activity at other sites demonstrate that this type of activity generally occurs in winter, at temperatures so cold that carbon dioxide, rather than water, is likely to play the key role.

HiRISE is operated by the University of Arizona, Tucson. The instrument was built by Ball Aerospace & Technologies Corp., Boulder, Colo. The Mars Reconnaissance Orbiter Project is managed for NASA's Science Mission Directorate, Washington, by NASA's Jet Propulsion Laboratory, a division of the California Institute of Technology in Pasadena.

For more information about HiRISE, see http://hirise.lpl.arizona.edu . For more information about the Mars Reconnaissance Orbiter, visit http://www.nasa.gov/mro.

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Here is a P-T phase diagram of CO2 that I found on the web and some background on its phase states.

https://encrypted-tbn0.gstatic.com/images?q=tbn:ANd9GcQhEU5kmgKDk1VjvPrvHA3e8eag5vJb0J0gwSIjHDi5wsyVDpZcUA

Carbon dioxide has no liquid state at pressures below 5.1 standard atmospheres (520 kPa). At 1 atmosphere (near mean sea level pressure), the gas deposits directly to a solid at temperatures below −78.5 °C (−109.3 °F; 194.7 K) and the solid sublimes directly to a gas above −78.5 °C. In its solid state, carbon dioxide is commonly called dry ice.

[neilwilkes]

Interesting find - the Phase States, I mean of course.
So I wonder what is really happening? If a chemist could jump ion & kindly tell us what would happen to C)2 at Martian pressure levels this would be most helpful as obviously a solid that goes from "dry ice" straight to gaseous form cannot possibly erode any gullies.....so we need to learn whether or not CO2 can exist as a liquid at any pressure/temperature combination.
It would also be interesting to know where the CO2 has come from - and if it is classified as a pollutant on Mars as well.