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.Minnetonka brown clogs with beading - womens 7.5 M , Cushion walk jazzy mule size 6AJ Valenci Red & White Sporty Mary Jane Ballet Flats 8 NEWMe Too Nini Bronze Colored Leather Ballet Flats Womens Shoes Sz 7MWOMEN'S CLARKS WAVE WALK BROWN LEATHER TOP STITCH BUTTON LOAFERS 9 N 86564L.L. Bean Black Leather Women's Shoes Clogs Size 9.5 ProfessionalBrown Suede Brindle Wool MERRELL ENCORE GROOVE WOOL BRINDLE WOOL Shoes US 6Tory Burch Eddie Slip On Ballet Flats Size 5 , SC35 Lizzie Pointed Toe Studded Slip On Flats 539, Zinc/Khaki, 6 US , NIB Antonio Melani Mack Ballet Flat Loafer Black Suede Studs Womens Sz 8 $79Talbots Womens Flat Sz 7 M Navy Blue Suede Leather Calf Hair Tassel Loafer ShoesWomen's Skechers Shape-Ups Sz 8.5 Silver/White Walking ShoesMinnetonka Womens Thunderbird II Caramel Deerskin Beaded Moccasin Size 6.5 , STEVEN by Steve Madden Women's Cuddles Fashion SneakerVintage NOS Messina Brown/Gold Mens Slippers Sz 10 New bt , Basket femme NO NAME tbé taille 37Easy Spirit e360 Rayfield Metallic Gray Sz. 9 Women's Athletic Shoes ~ MSRP $89 , Women Brooks Glycerin G13 Running Cross Training shoes size 7 USAnne Klein Womens Zasa Low Top Slip On Fashion Sneakers, White Multi, Size 6.0 w , Asics GEL Sonoma 3 Women’s Size 8 Gray/ Aqua Running Athletic Shoes F1-909 , Hoka One One Clifton Running Shoes Purple Women's (Size not Determined) (C4,2)Puma Suede Heart Reset - Blue - Womens , Asics Gel-Cadence White Black Blue Synethetic Mesh Running train Wo's US 9.5MSTEVEN Steve Madden Pace Espadrille Fashion Sneakers 576, White/Gold, 9.5 USTwisted X Boots Women's and man's :)? ?WDMS008 Driving Moc , New Balance Women's 860V7 Reflection With Poisonberry & Pigment Running Shoe 5.5NEW BALANCE WW813 WALKING SHOES - WOMEN'S SIZES 7 THRU 10 - BLACK- NEWNIKE Brown Leather Blazer Low Metro Sneaker Basketball Women's 10.5 NEWKenneth Cole New York Kam Fashion Sneakers 640, Light Grey, 10 US / 41 EU , Womens New Fashion Running Hiking Sport Shoes Breathable Walking Outdoor Shoes
"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."