We’ve spent the last 50 years exploring our cosmic neighbor Mars, but we are only just beginning to understand the complex, yet seemingly barren world. Thanks to a few intrepid space probes, we know Mars has water and some of it is locked up in icy polar caps, and some even lurks below the surface. Finding evidence of flowing water (even temporary flows) on the surface might mean Mars is a bit more habitable than previously thought. This week (September 28, 2015) scientists announced they detected the best evidence yet for liquid water flowing on the surface of Mars. So what does this mean? What can this discovery tell us about the implications for life?

Exciting and important science isn’t always about major discoveries, incremental results can be just as exhilarating as NASA proved yesterday. For years scientists were puzzled by the seasonal appearance of dark finger-like streaks spotted creeping down crater walls. Known as recurring slope linae (RSL for short), the streaks appear and even grow during the warmer months before fading away as temperatures drop. Scientists postulated that these enigmatic features were the result of transient salty water flows, but never had any supporting evidence – until now.

With the help of the Mars Reconnaissance Orbiter (MRO), scientists have detected the spectral fingerprints of hydrated perchlorate salts in the RSL. These chemical signatures indicate the features are caused by salty water flowing – and when we say flowing, we mean more like seeping – down the crater walls. In order to survive in liquid form on the surface of Mars (for any length of time), water would need to be extremely salty – which is what the evidence shows.

With some sort of liquid water still trickling on the Martian surface, does this mean it can support life? We know that some microbial communities can survive in similar conditions here on Earth, like the Atacama Desert, but what can that tell us about Mars? Truthfully, not much at this point. While they appear similar, we do not know enough about the conditions on Mars for a proper comparison. Also, the RSL are seasonal features so any sort of organism relying on them as a source of water would also need to be able to survive in their absence.

These sites could be some of the more promising locations to visit when looking for life on the Red Planet. But, studying these features up close and even looking for life in general on Mars will not be an easy feat, as reported by Lee Billings of Scientific American. The biggest threat to exploring any special region on another planet is the possibility of contamination. Earth's microbes are tenacious creatures capable of thriving in the most extreme conditions. We don’t want to inadvertently bring them along and contaminate what would be an otherwise pristine Martian sample.    

This is why we sterilize all our spacecraft prior to launch and take every precaution to prevent contamination. But even when we try our best, it’s not always good enough, as was seen with the Curiosity rover. NASA takes planetary protection seriously and even has an office dedicated to it. We may be able to somehow guarantee that the next rover we send to Mars is completely microbe-free, but it would be almost impossible for a human mission (the body has more bacterial cells than human ones). It is one of the reasons why Bill Nye and the Planetary Society have proposed a crewed orbital mission to Mars before we put boots on the ground.

Water on Mars also has big implications for future exploration. Once we’ve progressed to the point where we are regularly sending crews to Mars (which NASA and other agencies aim to do), having resources like water readily available will facilitate space travel. Water can be broken down into its constituents: hydrogen and oxygen, which can be used to create rocket fuel. Perchlorates, like the salts detected in this study, are present throughout the Martian soil and could also be used to make solid rocket fuel.

Exciting times are ahead as we continue to expand our knowledge of our nearest neighbor. “It seems that the more we study Mars, the more we learn how life could be supported and where there are resources to support life in the future,” Michael Meyer, lead scientist for NASA’s Mars Exploration Program at the agency’s headquarters in Washington said in a statement.