Slope lines in Hale Crater on Mars

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Salty water streams give further hint at life on Mars

Museum researcher Dr Joe Michalski says NASA discovery points to Martian environments that could be habitable by certain kinds of bacteria.

Research by NASA has concluded that dark streaks seen on the cliffs and craters of Mars might in fact be gullies formed by occasional salty water flows on the surface.

It's long been suspected that the narrow streaks, known as recurring slope lineae (RSL), are caused by seasonally flowing water. Natural History Museum Mars researcher Dr Joe Michalski says that the new paper published in the journal Nature Geoscience provides the best proof yet.

'These results provide strong evidence that salty water occasionally flows on the Martian surface, even today.

'The finding is yet another example of water on Mars, but a hugely important one because it points to environments that could potentially be habitable to certain kinds of bacteria', Michalski says.

As well as raising the prospect of bacterial life, the presence of water on the surface could also be of help to any future manned missions to the Red Planet.

Close view of the Hale Crater's slope lines on Mars

The recurring slope lineae, as they are known, are usually no wider than five metres, but can be up to a hundred metres long. © NASA/JPL-Caltech/University of Arizona.


Mystery solved

Earlier this year, a team from NASA and the European Southern Observatory released research concluding that around 20% of Mars was once covered by a vast ancient ocean, and that some of the water is still frozen in polar ice caps.

Evidence of liquid water on the surface today, however, has been harder to find. Because of the low atmospheric pressure and temperatures, any water present could not be pure H20.

But various salts that have already been detected on Mars (sulphates, chlorides and perchlorates) could potentially reduce the freezing point and evaporation rate of water, making it possible for a stable briny liquid to form on the surface.

For this latest discovery, scientists used sophisticated spectral imaging equipment aboard NASA's Mars Reconnaissance Orbiter to show that the hydrated salts were present at four locations where the slope lines were most extensive.

They say this strongly supports the idea that the streaks were formed by contemporary flows of briny water on the surface of Mars.

Slope lines on the Garni Crater on Mars

Scientists say that the narrow rivulets of water could potentially support bacterial life, and even aid future manned missions to Mars. © NASA/JPL-Caltech/University of Arizona.


Signs of life?

The slope lines are less than five metres wide, according to the researchers, and can be hundreds of metres long in some cases. They are also highly seasonal - they tend to appear and grow incrementally when the surface is warmer.

But despite being relatively small and fleeting, these streams of water could prove highly important in the search for life on Mars.

'We know from the study of extremophiles on Earth that life can not only survive, but thrive in conditions that are hyper-arid, very saline or otherwise “extreme” in comparison to what is habitable to a human. In fact, on Earth, wherever we find water, we find life,' says Michalski.

Michalski says that the findings also add to our understanding of the wider natural processes at work on Mars, raising the prospect of future manned missions to the planet.

'The discovery of active geological and hydrological processes elsewhere in the solar system underpins the point that these other worlds are actual places one could visit - where nature is happening every day.'