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New Gully on Mars Found: Photo

A NASA spacecraft has spotted a big gully on Mars, a feature that appears to have formed only within the last three years.

A NASA spacecraft has spotted a big gully on Mars, a feature that appears to have formed only within the last three years.

The powerful HiRISE camera on NASA's Mars Reconnaissance Orbiter (MRO) imaged the channel, which is found on the slope of a crater wall in the Red Planet's mid-southern latitudes, on May 25, 2013. The feature was not present in HiRISE photos of the area taken on Nov. 5, 2010. NASA unveiled the image on Wednesday (March 19).

While the Mars gully looks a lot like river channels here on Earth, it likely was not carved out by flowing water, NASA officials said.

PHOTOS: Mind-Blowing Beauty of Mars' Dunes

"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," officials wrote in a description of the gully image on Wednesday.

But, they added, "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."

However, MRO has observed other Martian features that do seem associated with liquid water - dark streaks known as recurring slope lineae.

RSL lines snake down crater walls and other slopes during warm weather on the Red Planet, and some researchers think they're caused by briny water that contains an iron-based antifreeze. Direct evidence of flowing water at RSL sites, however, remains elusive.

Photos: Weirdest Mars Craters Spotted by HiRISE

If water does flow across the surface of present-day Mars from time to time, the planet would be a likelier bet to host life as we know it. Here on Earth, life teems pretty much anywhere liquid water exists.

Ancient Mars was much more hospitable to life. For example, NASA's Curiosity rover discovered an ancient lake-and-stream system near its Red Planet landing site that could have supported microbial life billions of years ago.

Originally published on Space.com.

Photos: The Search for Water on Mars 7 Biggest Mysteries of Mars Ancient Mars Could Have Supported Life (Photos)

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This pair of before (left) and after (right) images from the High Resolution Imaging Science Experiment (HiRISE) camera on NASA's Mars Reconnaissance Orbiter documents the formation of a substantial new channel on a Martian slope between Nov. 5.

Mars plays host to a huge number of dune fields -- regions where fine wind-blown material gets deposited to form arguably some of the most beautiful dunes that can be found on any planetary body in the solar system. Using the powerful High-Resolution Imaging Science Experiment (HiRISE) camera on board NASA's Mars Reconnaissance Orbiter, planetary scientists have an orbital view on these features that aid our understanding of

aeolian (wind-formed) processes

and Martian geology. Here are some of our favorite Mars dunes as seen by HiRISE. Pictured here are shell-like "

barchan dunes

" in the ancient Noachis Terra region of Mars.

Special thanks to Ari Espinoza of the

HiRISE team at the University of Arizona

for helping to compile this list.

PHOTOS: The Weirdest Craters on Mars

Dunes of many shapes, sizes and formation processes can be found on the Red Planet. Shown here are elegant "

linear dunes

" with deposits of larger rocks and possibly ices in their troughs.

READ MORE: Sand Dunes Could Reveal Weather on Alien Worlds

These slug-like dark dunes are striking examples of "

dome dunes

" -- elliptical accumulations of fine material with no-slip surfaces. These domes contrast greatly with the often jagged appearance of barchan dunes. Found at the bottom of Proctor Crater, they are darker than the surrounding crater floor as they are composed of dark basaltic sand that was transported by the wind.

READ MORE: Slug-Like Dunes on Mars

Looking like a wind-blown silk sheet, this field of "star dunes" overlays a plain of small ripples, another aeolian feature. The ripples move more slowly across the bottom of Proctor Crater, so the large dune field will travel

over

the smaller ripples. Dunes are continuously evolving and moving with the wind, ensuring that the Martian surface is never static.

READ MORE: Bouncing Sands of Mars Blow in the Wind

These "transverse dunes" are undergoing seasonal changes. Likely entering Mars summer, this region of dunes is stained with pockets of subliming ices -- likely carbon dioxide. As the ices turn from solid to vapor, dune material slumps, revealing dark, sandy material underneath.

Resembling the mouths of a shoal of feeding fish, this is a group of barchan dunes in Mars' North Polar region. Barchan dunes betray the prevailing wind direction. In this case, the prevailing wind is traveling from bottom right to top left; the steep slope of material (plus dune "horns") point to the downwind direction. The HiRISE camera monitors barchans to see if they move between observing opportunities, thereby revealing their speed of motion across the Martian plains.

This is the same barchan dune field, zoomed out, a "swarm" of dunes covering the plains.

Not all barchan dunes "behave" and form neat "horny" shapes. They can become muddled and overlapping, creating "barchanoid dunes," as shown here.

This very fluid-looking collection of barchans is accompanied by a wind-blown ridge in the Hellespontus region of Mars but...

...only when zoomed out does the true nature of this fascinating region become clear. The prevailing wind is eroding the mesas (small hills) to the right of the image, carrying fine material downwind (from right to left), creating a startling pattern of barchans and a viscous-looking trail of sandy ridges across the plains.

The band Train sang about the "Drops of Jupiter" -- what about the "Drops of Mars"? Sure, they're not made of any kind of fluid, but they do make for incredibly-shaped dunes. These raindrop-shaped dunes are found in Copernicus Crater and are known to be rich in the mineral olivine, a mineral that formed during the wet history of Mars' evolution.

READ MORE: Mars' 'Raindrop' Sand Dunes Swarm

These craggy-looking dunes are old barchanoids eroding away through seasonal processes (sublimation of sub-surface ices) and the persistent Martian wind.

These linking barchan dunes are at the leading edge of a dune field -- grains of dust have been blown across a plain, deposited and left to accumulate in elongated arrow shapes.

Dome-shaped dunes and barchans seem to "reach out" and touch their downwind partners with slumped material.

Barchan dunes inside Arkhangelsky Crater in the southern hemisphere of Mars reveal a wind direction from top left to bottom right. Note the tracks of Martian dust devils over the dune slopes.

For more on the HiRISE camera,

see the HiRISE website

and

regularly updated Tumblr page

. For more on Mars dune definitions,

check out the USGS Mars Dunes site

.