ESA has published an image of Mars’ northern polar cap. It’s the composition of 32 images captured by the the Mars Express space probe’s High Resolution Stereo Camera (HRSC) instrument during as many passages above Mars’ north pole between 2004 and 2010. That mosaic shows the polar cap’s spiral-shaped troughs.
At Mars’ north pole there’s a perennial cap but when it’s winter, as it’s now, the temperatures can drop below -125° Celsius (-193° Fahrenheit) and about 30% of the carbon dioxide in the planet’s atmosphere freezes and adds a further meter-thick layer to the existing ice. When summer comes, the (very relative) warmth causes the sublimation of most of the carbon dioxide leaving the water ice layers.
Scientists think that the strong winds that sometimes are storms with speeds up to 400 kilometres per hour have an important role in creating the shapes of the ice sheet over time blowing from the center to the edges. The Coriolis force, the same that influences hurricanes on Earth, twists the Martian storms with the result that they have dug spiral-shaped troughs.
The regular enough shape of the ice cap is interrupted by Chasma Boreale, a large canyon about 500 kilometers long (about 310 miles), about 100 kilometers wide (about 62 miles) and about 2 kilometers deep (about 1.25 miles). Probably it’s a geological formation that existed before the spiral shapes but it’s not clear how it formed. The ice deposit around Chasma Boreale making the canyonlook deeper and deeper.
The polar ice cap was studied by NASA as well, using data collected by its Mars Reconnaissance Orbiter (MRO) space probe and in particular by its MARSIS and SHARAD instruments. They allowed to establish that the entire cap is composed of a series of individual layers of ice and dust. They form a kind of Mars’ climate archive of the last million years. If it were possible to collect a sample as they do on Earth with the polar caps’ ice it would be possible to carry out specific studies.
The Martian ice studies continue for the information they can provide about the history of the planet but also to understand which ones contain water in the solid state that could be used in future manned missions. The problem is not only in their position but also in the fact that ice water may contain various salts, which means that melting it won’t enough to use it.