Water Or Not? Fresh Martian Trenches Primarily Due To Carbon Dioxide Freezes, Study Says

by Elizabeth Howell on July 11, 2014

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Mars Reconnaissance Orbiter

Artist Illustration of the Mars Reconnaissance Orbiter

Does liquid water currently flow on the surface of Mars? Fresh-looking trenches on the Red Planet have come under a lot of scrutiny, including a 2010 study concluding that 18 dune gullies were primarily formed by carbon dioxide freezing.

A new study looking at several more gullies comes to about the same conclusion. Researchers examined images of 356 sites, with each of these sites captured multiple times on camera. Of the 38 of these sites that showed changes since 2006, the researchers concluded site changes happened in the winter — when it’s too cold for any liquid water to flow.

This image covers a location that has been imaged several times to look for changes in gullies.  This is in the Terra Sirenum region, part of the southern highlands in the mid-latitudes.  Credit: NASA/JPL/University of Arizona.

This image covers a location that has been imaged several times to look for changes in gullies. This is in the Terra Sirenum region, part of the southern highlands in the mid-latitudes. Credit: NASA/JPL/University of Arizona.

“As recently as five years ago, I thought the gullies on Mars indicated activity of liquid water,” stated lead author Colin Dundas of the U.S. Geological Survey’s Astrogeology Science Center in Arizona.

“We were able to get many more observations, and as we started to see more activity and pin down the timing of gully formation and change, we saw that the activity occurs in winter.”

Observations were made using NASA’s long-running Mars Reconnaissance Orbiter mission, which has been in orbit there since 2006. The researchers said that these lengthy missions are important for examining and confirming findings, because they can revisit data over time and change their conclusions, as needed, as more evidence comes in. Pictures were taken by the High Resolution Imaging Science Experiment (HiRISE) camera.

A 164-yard (150-meter) wide swath of Martian surface at 37.7 degrees south latitude, 192.9 degrees east longitude shows gullies changing between passes of the Mars Reconnaissance Orbiter. The earlier image, at left, was taken May 30, 2007. Near the arrows on the image on right, which was taken May 31, 2013, is a "rubbly flow" near the channel's mouth. Credit: NASA/JPL-Caltech/Univ. of Arizona

A 164-yard (150-meter) wide swath of Martian surface. It shows gullies changing between passes of the Mars Reconnaissance Orbiter. The earlier image, at left, was taken May 30, 2007. Near the arrows on the image on right, which was taken May 31, 2013, is a “rubbly flow” near the channel’s mouth. Credit: NASA/JPL-Caltech/Univ. of Arizona

The first images of gullies in 2000 sparked speculation that liquid water could be responsible for changing the surface today. It’s true that Mars has water frozen in its poles, and observations with several NASA rovers show strong evidence that water once flowed on the surface. But, these trenches are unlikely to show evidence that liquid water is flowing right now.

“Frozen carbon dioxide, commonly called dry ice, does not exist naturally on Earth, but is plentiful on Mars. It has been linked to active processes on Mars such as carbon dioxide gas geysers and lines on sand dunes plowed by blocks of dry ice,” NASA stated.

“One mechanism by which carbon-dioxide frost might drive gully flows is by gas that is sublimating from the frost providing lubrication for dry material to flow. Another may be slides due to the accumulating weight of seasonal frost buildup on steep slopes.”

The team added that smaller features could be the result of liquid water, such as this recent study using MRO. It’ll be interesting to see what other data is churned up as the fleet of orbiters continues making observations, and other scientists weigh in on the results.

The work will be published in the journal Icarus.

Source: Jet Propulsion Laboratory

About 

Elizabeth Howell is the senior writer at Universe Today. She also works for Space.com, Space Exploration Network, the NASA Lunar Science Institute, NASA Astrobiology Magazine and LiveScience, among others. Career highlights include watching three shuttle launches, and going on a two-week simulated Mars expedition in rural Utah. You can follow her on Twitter @howellspace or contact her at her website.

Aqua4U July 11, 2014 at 2:39 PM

Best place to look for liquid water on Mars? has got to be in Hellas Planetia! Lowest elevation on the Planet means it has a higher atmospheric pressure, therefore higher temperatures. Was created by a MAJOR impact that penetrated deeply and created a huge fracture zone. Those fractures and subsequent volcanic activity could mean there are lava tubes in the depression that may be tied to an aquifer bearing strata? Imagine hot mineral springs on Mars… wouldn’t THAT tip the scales toward way double extra groovy cool!

Aqua4U July 11, 2014 at 2:48 PM

SciFi short story subject? In future, Mars colonists cover the entire Hellas Planetia with a gigantic impermeable membrane and start to fill the basin with an atmosphere. The gases are generated by electrolyzing melted ice and with chemical gas reduction techniques to create nitrogen, CO2 and others.

i.e. We may not successfully terraform all of Mars.. just parts of it.

Jim E July 11, 2014 at 4:58 PM

Higher temperatures? Hellas Planetia is still extremely cold by Earth standards. It seldom gets above -50C. http://glx.net/~exile/marsweather.htm

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