Liquid water found on Mars, says Nasa

Curious lines running down slopes on the Martian surface may be streaks of super-salty brine, said the latest findings Monday in the scientific quest for extra-terrestrial liquid water, a prerequisite for life.

A team from the United States and France said it found evidence in the lines of "hydrated" salt minerals, which require water for their creation.

A handout image made available by Nasa on September 27, 2015, shows dark, narrow, 100 meter-long streaks called recurring slope lineae flowing downhill on Mars are inferred to have been formed by contemporary flowing water. Recently, planetary scientists detected hydrated salts on these slopes at Horowitz crater, corroborating their original hypothesis that the streaks are indeed formed by liquid water (AFP)

These results "strongly support the hypothesis" of liquid water on Mars today, concluded a research paper published in the journal Nature Geoscience.

Astrophysicists have long hypothesised that the seasonal streaks, dubbed "recurring slope lineae" (RSL), may be formed by brine flows on the Red Planet.

The lines, up to a few hundred metres in length and typically under five metres (16 feet) wide, appear on slopes during warm seasons, lengthen, then fade as they cool.

But spacecraft images have not been detailed enough to probe what is within the lines -- the pixel resolution is coarser than the width of the streaks.

A handout image made available by Nasa on September 27, 2015, shows the dark narrow streaks called recurring slope lineae flowing down the west facing slopes of Coprates Chasma in the equatorial region of Mars. These dark streaks flowing downhill on warm Martian slopes have been inferred to be contemporary flowing liquid water on Mars. Discovery of hydrated salts in these slopes have corroborated the liquid water hypotheses. (AFP)

In April, scientists reported in the same journal that perchlorate salts, like the ones in the new study, were "widespread" on the surface of our planetary neighbour and humidity and temperature conditions just right for salty brines to exist.

Perchlorate is highly absorbent and lowers the freezing point of water so that it remains liquid at colder temperatures.

A handout image made available by Nasa on September 27, 2015, dark narrow streaks called recurring slope lineae emanating out of the walls of Garni crater on Mars. The dark streaks here are up to few hundred meters in length. They are hypothesized to be formed by flow of briny liquid water on Mars. (AFP)

The new study found signs of these same salts in the enigmatic streaks.

"What our paper does is further substantiate that theoretical possibility" of liquid brines on Mars, co-author Lujendra Ojha of the Georgia Institute of Technology in Atlanta told AFP by email.

'Almost' proof

The team devised a method to extract more data from individual pixels in images from the Crism spectrometer instrument on Nasa's Mars Reconnaissance Orbiter, and found details "consistent with the presence of hydrated salt minerals that precipitate (crystallise) from water," according to a Nature press release.

"The findings strongly suggest a link between the transient streaks on Martian slopes and the flow of liquid brines," it added.

Asked if the data was unequivocal proof of liquid water on Mars, another of the study authors, Alfred McEwen from the University of Arizona, told AFP: "I would say almost".

But if there was, it was likely "wet soil, not free water sitting on the surface," he said by email.

It is widely accepted that the Red Planet once hosted plentiful water in liquid form, and still has water today, albeit frozen in ice underground.

Earlier this year, Nasa said almost half of Mars' northern hemisphere had once been an ocean, reaching depths greater than 1.6 kilometres (one mile).

But 87 per cent of the precious substance was lost to space.

Liquid water found on Mars: Nasa

Liquid water has been observed on the planet Mars which makes it far more likely that life could be found there, the US space agency Nasa said Monday.

"Mars is not the dry, arid planet we thought of in the past," Jim Green, Nasa's planetary science director, told a press conference.

"Under certain circumstances, liquid water has been found on Mars."

Scientists have long speculated that there may once have been life on the Red Planet. The presence of liquid water makes it possible that life could currently exist there, Nasa said.

"The really exciting thing about this is that our view of this ancient Mars, and the possibility of life originating on Mars, had been really about seeking chemical fossils of possible past life on Mars," said astronaut John Grunsfeld, who is also associate administrator of Nasa's science mission directorate.

"The existence of liquid water on Mars -- even if it's super salty briney water -- gives the possibility that if there's life on Mars we have a way to describe how it might survive."

With several missions to Mars already in the planning stages, the question of whether there's life on the planet is now "a concrete one we can answer," Grunsfeld said.

The presence of water will also make it easier to send a manned mission to Mars, which Nasa aims to do in the 2030s.

"To be able to live on the surface, the resources are there," Grunsfeld said.

Water is "critical" he said, but the planet also offers other key elements like nitrogen which could be used to grow plants in greenhouses and the types of salts that could be used to make rocket fuel.

The announcement comes days before the blockbuster film "The Martian" opens in which Matt Damon manages to survive on his own after being left for dead with about a month's supply of food.

Scientists have long believed that water once flowed across the Red Planet and formed its valleys and canyons, but a major climate change about three billion years ago changed that.

"Today we're revolutionizing our understanding of this planet," Green said.

"Our rovers are finding there's a lot more humidity in the air."

The rovers have also found that the soil is more moist than anticipated.

In 2010 scientists observed dark streaks running down Martian slopes. They suspected that the streaks -- which would form in spring, grow by summer and then disappear by fall -- could be water.

"It took multiple spacecraft over several years to solve this mystery, and now we know there is liquid water on the surface of this cold, desert planet," said Michael Meyer, lead scientist for Nasa's Mars exploration program.

"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."

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