A really interesting set of images taken by NASA’s Mars Reconnaissance Orbiter was announced this past week. Here’s one of Newton Crater taken from orbit and edited with 3D modeling1 to better show the slopes at the edge of the crater. The most interesting and relevant parts of the picture are the dark lines appearing on the surface.
What makes these dark features really intriguing is that they are seasonal. They begin to appear and then extend down slope in spring and into the summer. Then in winter, they disappear completely, to return again the following spring. The best explanations that the researchers have been able to offer for this discovery is the flow of briny water. If true, this will be the first instance that we have found liquid water on Mars2.
The flows are on the order of just a few meters wide and occur on the brighter slopes, where there is more sunlight. The locations and temperatures of these features reduced the possibilities of what they could be. This could have indicated the presence of carbon dioxide frost, but the sites where the flows were found were simply too warm. The presence of pure liquid water was ruled out as well, since temperatures at most sites were too low for water to exist as a liquid. This led to strong evidence for liquid brine: the presence of salt in the water would lower its freezing temperature, allowing it to flow.
Yet, the dark lines appearing on the surface were not occurring because it was getting wet. Spectrometers onboard the orbiter could not find any signs of water on the surface below. This suggests that the darkness must be appearing for some other reasons. A possibility suggested by researchers is that the flow of water may be under the surface and could be altering the way grains on the surface are reflecting light, making the area appear darker. There still are no strong models as to what process is exactly making the surface darker and why the areas regain their brightness during the winter.
Of course, this news is exciting for those who are keen on finding traces of life on Mars. For me, though, the research is much more intriguing because of the implications it has about Mars as a planet. Finding flowing water on Mars, among the other great discoveries made recently, have painted the red planet to be much more different and interesting than I had ever imagined. Certainly, the presence of life would be exciting, but I find it no less exciting to see Mars have liquid water and the implications that has for other similar planets found outside our Solar System.
And like most images released to the public by NASA, the color has also been “enhanced”. ↩
There has been strong evidence for the presence of water on Mars, with frozen water located in Polar regions, and perhaps even flowing water in Mars’ history. This discovery lends evidence towards liquid water on Mars right now. ↩