Unless you’ve been sleeping under a rock you’ve no doubt seen the announcement by NASA today that water has been discovered on Mars (sort of, but we’ll get to that in a moment). After a day of sensational hype created from NASA’s pre-warning of an important press release, this was making headlines from the word go, with everyone speculating on the topic of discussion. The discovery of aliens, mysterious artefacts and water on Mars were all proposed.
Here is one of the images which helped make the discovery. Images of the same part of Mars’ surface at different times shows these streaks appearing between shots, indicating an active landscape. The dark streaks are on the order of 5 metres wide, often narrower, were first discovered over a decade ago, and have been called ‘recurring slope lineae’. There were numerous proposed causes for these, including water, but also avalanches or grains of material rolling down slopes.
Once the CHRISM spectrometer was applied to these streaks, the spectral signature of the features could be analysed, revealing their composition. Hydrated salts were found on every streak, but were strikingly absent from the surrounding surface. Water turns to liquid on Mars’ surface at 0 degrees Celsius, just as it does on Earth, but water with a high concentration of salts will melt at much lower temperatures (try this at home with some table salt!). The flows appear when temperatures rise over -23 degrees Celcius, which is reached during the warm season in parts of Mars.
Researchers are working on determining where this water has come from. Possible theories include porous rocks under the surface and saline aquifers existing in some areas below the surface in areas. Alfred McEwen, a planetary geologist, prefers the theory that the salts exist on the surface of Mars, and absorb water from the atmosphere until they reach a point where they have enough liquid to flow downhill, a process known as deliquescence. To me this would indicate that the surface of Mars where these features form would be laden in salts, but as mentioned earlier the spectral imagery does not seem to support this theory.
So why sort of? To be precise, we haven’t directly detected water flowing on Mars, only signs (however promising) that point towards water flow. But we must always be cautious and consider other processes that may create the same results (or even processes we have never encountered before!).
“Does this mean life on Mars?” everyone cries. The presence of liquid water (however transient in this case) is a good sign for the existence of life. Dr Grunsfeld of NASA has stated that “If I were a microbe on Mars, I would probably not live near one of these [sites]”. He suggests that underneath a freshwater glacier, such as those suspected in the north and south, would yield more ideal conditions for life.
In any case, these are certainly exciting times for Mars exploration. Of course, a ground-truthing experiment (physically checking these sites, drilling and collecting samples) would prove this theory right or wrong. Here’s to hoping we can get a geologist to these sites soon! If anyone asks, pick me.