The US space agency Nasa has confirmed that new findings from its Mars Reconnaissance Orbiter (MRO) had provided “the strongest evidence yet that liquid water flows intermittently on present-day Mars".

“Mars is not the dry, arid planet we thought of in the past," Jim Green, director of Nasa’s planetary science division, said at a press conference on Monday.

“Under certain circumstances, liquid water has been found on Mars," he announced. The water that Green refers to has been described by scientists as “a very small amount—maybe just enough to wet the top layer of the surface of Mars".

“Using an imaging spectrometer on MRO, researchers detected signatures of hydrated minerals on slopes where mysterious streaks are seen on the Red Planet. These darkish streaks appear to ebb and flow over time. They darken and appear to flow down steep slopes during warm seasons, and then fade in cooler seasons. They appear in several locations on Mars when temperatures are above minus 10 degrees Fahrenheit (minus 23 Celsius), and disappear at colder times," Nasa said in a press release. The streaks, are reported to be approximately 4 to 5 meters wide and 200 to 300 meters long.

The Nasa press release added, “These downhill flows, known as recurring slope lineae (RSL), often have been described as possibly related to liquid water. The new findings of hydrated salts on the slopes point to what that relationship may be to these dark features. The hydrated salts would lower the freezing point of a liquid brine, just as salt on roads here on Earth causes ice and snow to melt more rapidly. Scientists say it’s likely a shallow subsurface flow, with enough water wicking to the surface to explain the darkening."

It quoted astronaut and associate administrator of Nasa’s science mission directorate in Washington, John Grunsfeld, as saying, “Our quest on Mars has been to ‘follow the water’ in our search for life in the universe, and now we have convincing science that validates what we’ve long suspected. This is a significant development, as it appears to confirm that water—albeit briny—is flowing today on the surface of Mars."

The latest findings come five months after scientists found the first evidence for liquid water on the red planet. In April this year, as Vox reports, “Using data collected by the Curiosity rover, they determined that tiny amounts of water vapor condense as a liquid in the planet’s soil at night and evaporate away in the morning."

On an immediate level, Monday’s discovery has handed a significant boost to scientists, seeking to explore the possibility of life on Mars. “We think liquid water is essential for life (at least as we know it). That does not mean that life is there; but, it’s a good place to look," said Rich Zurek, chief scientist, Nasa Mars Program Office, and project scientist, MRO in a Reddit Ask Me Anything (AMA) session soon after the findings were announced.

He added, “Liquid water, even if very salty, is still a good place to look for life forms. We don’t know how robust martian life (if it exists) could be. Also, water in any form is a resource that future missions could exploit."

The findings are in sync with Nasa’s ambitious project to send humans to Mars in the 2030s, in accordance with the Nasa Authorization Act (2010) and the US National Space Policy. Zurek said, “Presently, Nasa is looking into the possibility of sending humans to the vicinity of Mars in the early 2030s. In this scenario, the earliest humans to the surface would be in the late 2030s."

The discovery of liquid water, therefore, could be a big boost for astronauts visiting the planet. Based on further research and findings, humans could well be drinking water on Mars, or use it for creating oxygen and rocket fuel, or to water plants in greenhouses.

But as of now that can’t be done. Several salts, like magnesium or sodium perchlorate have been detected on Mars. While these, as Zurek said, are not “typical salts on earth", they do help “keep water liquid to the much colder temperatures which occur on Mars". The water, given its briny nature, is not fit for human consumption. He adds, “To be a future resource for humans, you would want to remove the salts."

Water on Mars: A brief history

The brouhaha over the possibility of water on Mars dates back to the 19th century when Italian astronomer Giovanni Schiaparelli found “canalis" or channels, described as hazy streaks, on the surface of Mars. However, as an article in Time pointed out, ‘canalis" was wrongly translated as canals which suggested that someone had chosen to build them.

Over the years, images seen via telescope suggested the presence of canals and polar snow caps. P.M. Ryves, a British astronomer, is quoted in the same story as saying that Mars “appears to be far from a dead world,". “Whether it is inhabited by intelligent beings like ourselves is perhaps the most absorbent question that confronts the human race," he added.

However, without any substantial photographic evidence of any sign of water on Mars, the subject has always been a controversial issue among scientists. Hazy images of the canalis were suggestive of vegetation while some scientists believed that the polar snow caps did not have snow or ice but were thought to be made of frozen carbon dioxide.

By 1976, scientists changed their minds again. Data sent by the Viking 2 orbiter revealed “the summer ice cap of Mars’ North Pole is composed of frozen water," Time explained, adding that “the discovery confirms that Mars has far more water than had previously been believed, and suggests that even more lies in a shell of permafrost below the planet’s rocky surface. In fact, scientists said, the polar caps might be merely the visible tips of an iceberg-like Mars."

However, by the 2000s, there was stronger evidence to suggest the existence of water on the red planet.