In a highly anticipated announcement made on Monday morning, NASA scientists unveiled the strongest evidence yet that, under certain circumstances, liquid water flows on Mars.
The findings come from NASA’s Mars Reconnaissance Orbiter (MRO), which was launched on 12 August 2005, and attained Martian orbit on 10 March 2006. The MRO contains scientific instruments including cameras, spectrometers, and radar, which together analyse the landforms, rock and mineral layers, and ice of Mars, and monitor the planet’s daily weather and surface conditions.
Using an image spectrometer on the MRO, researchers have detected the signatures of hydrated salts on Mars which they believe provide evidence of liquid water. These hydrated salts occur on steep slopes, and are indicated by dark streaks on the surface of the Red Planet, which appear to form in late spring, growing through the summer, and disappearing by fall. Hydrated salts lower the freezing point of liquid brine; and researchers think it likely that a shallow subsurface liquid flow is the cause of the surface darkening. The visible downhill flows, which can run up to a few hundred metres in length, are known as recurring slope lineae (RSL).
The lead author of the report setting out the findings, which were published today by Nature Geoscience, is Lujendra Ojha of the Georgia Institute of Technology. Ojha first began studying the streaks on the surface of Mars back in 2010, as a University of Arizona undergraduate, working on images from the MRO’s High Resolution Imaging Science Experiment (HiRISE). The report has eight co-authors.
Geologic evidence suggests that water has played a significant part in Mars’ history, and earlier this year NASA scientists produced research positing a massive ancient ocean, once covering a fifth of the planet’s surface, 20 million cubic kilometres of water spread across the northern hemisphere. Frozen water persists at the planet’s north polar ice cap. But despite recent hints, this is the clearest indication yet that present-day Mars is wet.
Scientists remain uncertain where the liquid water may be coming from: seeping up to the surface from underground aquifers, frozen in the winter but melting come summer, or else absorbed from the atmosphere. The evidence of seasonal flows of water, and the indication that this water is briny rather than pure, together afford no guarantees of life: it is possible that the water is simply too salty for life to be sustained. While flowing water on Mars could be harnessed to aid further exploration, the possibility of Martian life also poses challenges: space agencies will have to strive to prevent any contamination from microbes from earth.
Still, the announcement marks a momentous step in the study of Mars and in our understanding of space. James L. Green, Director of NASA’s Planetary Science Division, remarked:
‘This is tremendously exciting. We haven’t been able to answer the question, ‘Does life exist beyond Earth?’, but following the water is a critical element of that. We now have, I think, great opportunities to be in the right locations on Mars to thoroughly investigate them.’