PARIS - Salty water just below the surface of Mars could hold enough oxygen to support the kind of microbial life that emerged and flourished on Earth billions of years ago, researchers reported Monday (Oct 22).
In some locations, the amount of oxygen available could even keep alive a primitive, multicellular animal such as a sponge, they reported in the journal Nature Geosciences.
"We discovered that brines" - water with high concentrations of salt - "on Mars can contain enough oxygen for microbes to breathe," said lead author Vlada Stamenkovic, a theoretical physicist at the Jet Propulsion Laboratory in California.
"This fully revolutionises our understanding of the potential for life on Mars, today and in the past," he told AFP.
Up to now, it had been assumed that the trace amounts of oxygen on Mars were insufficient to sustain even microbial life.
"We never thought that oxygen could play a role for life on Mars due to its rarity in the atmosphere, about 0.14 per cent," Stamenkovic said.
By comparison, the life-giving gas makes up 21 per cent of the air we breathe.
On Earth, aerobic - that is, oxygen breathing - life forms evolved together with photosynthesis, which converts CO2 into O2. The gas played a critical role in the emergence of complex life, notable after the so-called Great Oxygenation Event some 2.35 billion years ago.
But our planet also harbours microbes - at the bottom of the ocean, in boiling hot springs - that subsist in environments deprived of oxygen.
"That's why - whenever we thought of life on Mars - we studied the potential for anaerobic life," Stamenkovic.
LIFE ON MARS?
The new study began with the discovery by Nasa's Curiosity Mars rover of manganese oxides, which are chemical compounds that can only be produced with a lot of oxygen.
Curiosity, along with Mars orbiters, also established the presence of brine deposits, with notable variations in the elements they contained.
A high salt content allows for water to remain liquid - a necessary condition for oxygen to be dissolved - at much lower temperatures, making brines a happy place for microbes.
Depending on the region, season and time of day, temperatures on the Red Planet can vary between minus 195 and 20 deg C.
The researchers devised a first model to describe how oxygen dissolves in salty water at temperatures below freezing.
A second model estimated climate changes on Mars over the last 20 million years, and over the next 10 million years.
Taken together, the calculations showed which regions on the Red Planet are most likely to produce brine-based oxygen, data that could help determine the placement of future probes.
"Oxygen concentrations (on Mars) are orders of magnitude" - several hundred times - "greater than needed by aerobic, or oxygen-breathing - microbes," the study concluded.Clarks collection womens flip flops blackSoftspots Constance Lite Slip On Navy Womens Size 9.5Birkenstock Women’s 8/39 Fisherman Black Sandals Shoes , Lucky Brand Womens Emmie Blue Ballet Flats Shoes 6 Medium (B,M) BHFO 7720 , POE POWER OF ESSENTIALS LADIES BLACK SHOES-7.5M-BARELY WORN-PATENT/NET-GREAT , Ladies Lifestyle by Cushion Walk,bronze leather,slip on,bow on front, rochdale , Born Gold Flats Loafers Womens Shoe Size 6 , COMFORT PLUS BY PREDICTIONS ETTA BLACK FABRIC WEDGE SLIP ON LOAFERS 10 NEWWomen's NaturalSoul Naturalizer LEATHER Tan SANDALS SHOES 2" HEEL Size 8 M - EUC , Enzo Angiolini Womens Lianne Closed Toe Loafers, Black, Size 8.0 wdWPLand's End Blue Teal Aqua Suede Flats sz 8 M Ballet Loafer Perfect Soles , Levi's Drea Women's White/Grey Fashion Sneakers 6MNot Rated Womens Coza Open Toe Slide Flats, Nude, Size 8.0 NeHSSimpsons Duff King Velour Full Slippers Novelty Homer Beer Mens Slip On , Womens ADIDAS HONEY HI W Blue Trainers Q33727 , NEW PUMA Roma Ripstop Clear Womens Sneakers Shoes 10.5 White/Capri Breeze $80 , New! Women's Skechers 12404 Empire - Heart to Heart Walking Shoe - Grey/Mint O39 , Saucony Womens Running Shoes Size 7 (C,D,W) (15416)Nike Wmns Air Force 1 HI SE Black/Dark Gray-Cobblestone 860544-003 , Nike Revolution 2 Women's Running Athletic Shoes Size 10 M , Chic Womens Wedge Heel Canvas High Top Platform Sneakers Sandals Open Toe Shoes , J/Slides Camel black Floral Sneaker size 8.5 NIB , Puma Size 7 White Leather Sneakers New Womens Shoes , Under Armour Women's Favorite Cotton Everyday Long Sports Bra - Choose SZ/Color , Marc Jacobs Hip Retro sneakers, 8.5, leather , Skechers Womens Relaxed Fit Valeris Flying High Sneakers,Black / Hot Pink,6.5Ecco Biom Performance Train Athletic Shoes Women Size 10 () , New Balance Womens Running Classics Shoes Sneakers BLACK WL520BK Womens 10.5Merrell Womens Jungle Moc Leather Slip-On Leather Casual Loafer Shoes Size 9Volcom Stone High Top shoes Black & White Womens Size 9
"Our results do not imply that there is life on Mars," Stamenkovic cautioned. "But they show that the Martian habitability is affected by the potential of dissolved oxygen."