Does water boost chances of extraterrestrial life?
Following NASA's announcement on 28 September 2015 regarding Martian water, NASA's associate-administrator for science John Grunsfeld, talked of sending a spacecraft in the 2020s to directly look for life on Mars. "The existence of liquid water, even if it's super-salty briny water, gives the possibility that if there's life on Mars we have a way to describe how it might survive", Grunsfeld said.
Seasonal dark streaks on slopes in Mars were noticed by an undergraduate student of the University of Arizona in 2010, from images taken by the Mars Reconnaissance Orbiter (MRO). The streaks lengthened in summer and disappeared in winter. Dr. McEwen, who was the primary investigator and his colleagues conjectured that the streaks were caused by the flow of extremely salty water down the slopes.
One of the essential ingredients for the emergence of life is considered to be liquid water. According to Jim Green, director of Planetary Science at NASA, "following the water is a critical element" in the search for extraterrestrial life.
NASA scientists announced evidence of the existence of a massive Martian ocean billions of years ago. According to evidence, the ocean covered nearly one-fifth of the Martian surface, and held 20 million cubic kilometres of water, making it larger than the Arctic Ocean. Only 13% of the water now remains, frozen in Mars' polar ice caps, while the rest was lost to space.
The massive ocean in Mars, believed to have been formed soon after Mars' formation 4.5 billion years ago, existed for over 1.5 billion years - which is longer than it took for life to emerge from the earth's oceans.
On 7 April 2015, NASA Chief Scientist, Ellen Stofan said, "I think we're going to have strong indications of life beyond Earth within a decade, and I think we're going to have definitive evidence within 20-30 years." Stofan's claim is supported by evidence of an abundance of water in the Milk Way - from Mars' ancient oceans to Jupiter's moons to interstellar clouds.
According to new measurements by NASA's Curiosity Rover which landed on Mars in 2012, Mars could have sub-surface liquid water. Curiosity's instruments found a salt (calcium perchlorate) which, according to researchers, could absorb frost from the Martian surface and melt it to form a thin layer of liquid brine. This could then have sunk into the Martian soil. However, direct evidence was still lacking.
Recurring Slope Lineae or dark streaks in Mars had been associated with liquid water since 2011. The suspicion was confirmed on 28 September 2015, after the discovery of hydrated salts called perchlorates on the Martian surface in readings taken by MRO. This discovery is a "direct detection of water", as liquid water had to have been recently present to produce the hydrated salts.
The dark streaks appear on Mars when temperatures are above minus 23 degrees Celsius, and disappear during colder seasons. The hydrated salts decreases the freezing point of water allowing it to flow during relatively warmer seasons.