What does this mean for life?
Nothing definitive. Yet.
Dr Manish Patel from the Open University explained: “We have long since known that the surface of Mars is inhospitable to life as we know it, so the search for life on Mars is now in the subsurface.
“This is where we get sufficient protection from harmful radiation, and the pressure and temperature rise to more favourable levels. Most importantly, this allows liquid water, essential for life.”
This principle of following the water is key to astrobiology – the study of potential life beyond Earth.
So while the findings suggest water is present, they don’t confirm anything further.
“We are not closer to actually detecting life,” Dr Patel told BBC News, “but what this finding does is give us the location of where to look on Mars. It is like a treasure map – except in this case, there will be lots of ‘X’s marking the spots.”
The water’s temperature and chemistry could also pose a problem for any potential martian organisms.
In order to remain liquid in such cold conditions (the research team estimate between -10 and -30 Celsius where it meets the ice above), the water likely has a great many salts dissolved in it.
“It’s plausible that the water may be an extremely cold, concentrated brine, which would be pretty challenging for life,” explained Dr Claire Cousins, an astrobiologist from the University of St Andrews, UK.