Yesterday NASA announced the existence of flows of liquid water on Mars. The study, just published in the journal “Nature Geoscience”, is based upon years of analysis of data collected mainly thanks to the NASA’s MRO (Mars Reconnaissance Orbiter) space probe. The images captured by its camera and spectrometric data allowed to find streams of water along the walls of craters and slopes that vary over time and perchlorate salts in them.

Past studies allowed to collect evidence that water flowed on Mars in the distant past but today the red planet seemed totally barren. However, Lujendra Ojha of Georgia Tech (Georgia Institute of Technology) in 2010 noted some elements of the Martian terrain photographed by the MRO space probe that left him perplexed. They seemed to show seasonal changes associated with what looked like streaks.

By studying the photographs captured by the HiRISE (High Resolution Imaging Science Experiment) camera with the mapping of the minerals using another MRO’s instrument, CRISM (Compact Reconnaissance Imaging Spectrometer for Mars), Ojha and his team discovered the signature of perchlorate salts corresponding to relatively wide streaks.

These salts can form stable hydrated compounds and are a sort of natural antifreeze since they can bring water’s freezing point down to -70° Celsius (-94° Fahrenheit). This is crucial in an environment like that of Mars, where the atmospheric pressure is very low so water on the surface would evaporate immediately.

Perchlorate salts might absorb moisture from the atmosphere but the layer that would be formed would be really thin. The streaks observed, also known as recurring slope lineae (RSL), need a lot more water to be fed and at the moment there are no explanations of its origin. For the moment there are several hypotheses but none can explain alone the formation of water streaks.

The discovery of these seasonal flows on Martians slopes is an important moment in the research on the red planet. The data collected by the MRO space probe were crucial but the reconstruction of Mars history was made and keeps on being made from data collected by the other probes and the various landers and rovers landed over the decades.

The fact that today there’s liquid water on Mars relaunches the possibility that there are life forms. However, the data are still limited so there are many opinions and hypotheses but it will take more time before we can have verifiable theories. In the coming years, ESA and NASA will send even new rovers more sophisticated than Curiosity to Mars and their instruments could finally give an answer.