Future Mars colonists may tap exposed ICE CLIFFS for water
Friday, January 12, 2018, 17:25 - Finding water or ice on Mars is becoming fairly commonplace these days, but this is a new one: researchers are reporting that they've spotted tall cliffs, up to 100 metres (328 feet) high, made of nearly pure water ice in several locations on Mars!
NASA's Mars Reconnaissance Orbiter (MRO) has been circling the Red Planet for over 10 years now, sending back amazing pictures of the Martian surface, using its High Resolution Imaging Science Experiment (HiRISE) camera. In that time, it has provided us with the most detailed maps of Mars we have yet, as well as revealing the composition of the surface features, including finding deposits of clay, gypsum and other minerals.
The most recent discovery is different, though, and provides some added hope for the success of future human exploration of the Red Planet.
Scientists examining the images send back by MRO have found eight different locations on Mars that reveal immense deposits of almost pure water ice, which lie just 2 metres (6.5 feet) below the surface. This discovery came from spotting the edges of these deposits, which are eroding away to form tall cliffs that expose the ice to the thin Martian air.
"There is shallow ground ice under roughly a third of the Martian surface, which records the recent history of Mars," said the study's lead author, Colin Dundas of the U.S. Geological Survey's Astrogeology Science Center in Flagstaff, Arizona. "What we've seen here are cross-sections through the ice that give us a 3-D view with more detail than ever before."
At this wedge-shaped pit on Mars, the steep slope (or scarp) at the northern edge (toward the top of the image) exposes a cross-section of a thick sheet of underground water ice. Credit: NASA/JPL-Caltech/UA/USGS
Although HiRISE images appear black and white when viewed separately, each image is taken using a special filter, which focuses on one part of the spectrum of light. By combining different images together, as shown above, the composite images can reveal the subtle differences in how the surface absorbs and reflects light, and thus provide information about what makes up the surface.
According to NASA, the gray-scale portions of the image, on the left and right, are only from the red-light portion of the visible spectrum. The colour section in the middle, is a combination of images, that filter for red, near-infrared and blue-green wavelengths of light. With this combination, normal surface dust and minerals come out as the peach colour, while water ice stands out bright blue. The researchers didn't leave this to simple colour interpretation, though. They used MRO's Compact Reconnaissance Imaging Spectrometer for Mars (CRISM) to verify that these locations revealed the spectral signature of water.
"The discovery reported today gives us surprising windows where we can see right into these thick underground sheets of ice," Shane Byrne of the University of Arizona Lunar and Planetary Laboratory, a co-author on the report, told NASA on Thursday. "It's like having one of those ant farms where you can see through the glass on the side to learn about what's usually hidden beneath the ground."
A close-up of the false colour portion of the above image, focusing in on the scarp to reveal the details. Credit: NASA/JPL-Caltech/UA/USGS
This exposed ice is slowly sublimating away, turning directly from solid to vapour, because even though temperatures on Mars are well below freezing, the air pressure is too thin for the ice to hold its solid shape. The size of the deposit, however, means that it will be a very long time before it completely sublimates into the atmosphere. This makes these sites very valuable, for the climate science they contain locked away in their layers, and as a potential water source for when humans eventually land on Mars, and attempt to establish colonies there.
A lander or rover sent to drill down into one of these locations could provide us with a detailed chronology of Mars' past climate, and according to Byrne, "Astronauts could essentially just go there with a bucket and a shovel and get all the water they need."