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New high-resolution images taken last month of Mars’ south polar region are revealing signs of spring that are decidedly Martian.

The image above features a spider trough network left behind as seasonal dry ice caps have sublimated away in the warmer temperatures. It’s part of a new series of images released this week by the University of Arizona’s High Resolution Imaging Experiment, or HiRISE, aboard NASA’s Mars Reconnaissance Orbiter.

See more information and photos below.

The gas beneath the ice cap can flow in the same places year after year, eroding troughs in the surface of the planet.

“What happens on Mars, we think, is that as the seasonal ice cap thins from the bottom, gas underneath the cap builds up pressure,” said HiRISE deputy principal investigator Candice J. Hansen-Koharcheck of the NASA Jet Propulsion Laboratory in Pasadena, California.

“And where gas under the ice finds a weak spot or a crack, it will flow out of the opening, often carrying a little dust from the surface below.”

The next HiRISE image shows how dust that has been carried to the surface by gas jetting through the ice cap is blown about by prevailing winds before settling in fan-shaped deposits atop the ice cap. Varying orientations suggest that as the ice layer thins, a set of gas jets becomes active, they die down, then further away another set starts up at a later time with a different prevailing wind direction.

Many jets appear to be active at the same time since numerous fans are all deposited in the same direction: this next, closer image is an example of such an occurrence.

This southern hemisphere crater has gullies on its north and northeast walls. Gullies are proposed to be carved by liquid water originating from the subsurface or melting ice/snow on the surface.

Dark dunes are visible on the crater floor. Lighter, smaller dunes rim the south side of the crater floor. The entire scene, pictured below, has a pitted texture, suggesting that ground ice was once present in this region. When ground ice sublimates (goes from a solid directly to a gas), it leaves behind empty spaces in the soil that turn into pits as the remaining overlying soil collapses to fill them.

The full set of new HiRISE Mars images is here. Check out all the downloadable formats and sizes, with some even designed to fit an iPhone screen!

Source: Lori Stiles, at the University of Arizona