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.02-2908 Geox Women's D Janalee H Loafers, SIZE 7.5MERRELL "Polar Moc Waterproof" Ladies Black Slipon Loafer Size 9US 40EU , Anne Klein KK Davis Women's Black Suede Moccasin Boat Shoe Loafers Size 8 MNew Womens Tan Ballet Flat with Gold Tip Bow Detail Slip-on Shoes Sizes 5-10 US , Clarks Womens Ashland Ice Loafers Shoes Black 26069440 Size 8.5 , Bernie Mev EU38 US 7.5 /8.Metallic Bronze Gold Woven Black Suede Ballet Flats , Hot Chocolate Design Chocolaticas Patilla Women's Mary Jane Flat Multicoloured , B35 Hint Slip-On Sneakers 340, White, 9 US , Cole Haan Womens Siennasam Closed Toe Loafers Pink Size 6.0 , Marc Joseph New York Womens wall street Closed Toe Navy Grainy Size 8.0 0zJG , Kappa Women’s Shoes (Size 6.5 US) White Pink Blue (Free Ship Canada) SneakersWomens Asics GT 2150 Running Shoes, Size 9.5Superga 2750 Rope Womens Violet Canvas Trainers , New Balance WX577v4 Training Shoes - Women's Size 8.5 B - Black , PATAGONIA Tenzing Seagrass Womens 8 Running Trail Training Shoes Green G03(833657-005) WOMEN'S NIKE CLASSIC CORTEZ LEATHER PRM BLACK/BLACK/IVORY SZ-11 , NEW Nike Blazer Mid Premium Athletic Sneakers Black Wn's Sz 7.5 (403729-007) , Women's Asics Nimbus 19 Gray Black Running Shoes Size 7.5 , Women's New Balance 860v6 Light Blue/Dragonfly W860BP6-Narrow WidthWomen's New B , Tretorn wt Carry2 New Grafite wtCarry2 Women's , NEW Asics Women's Size 10 Gel-195Tr Ankle-High Cross Training Running Shoes NWT , New Balance WRUSHPK2 - Women's Vazee Rush v2 Running ShoeNike Classic Cortez wmns trainers sneakers 749864 310 eu 40 us 8.5 NEW , Womens Converse Navy Blue Chuck Taylor All Star High Top M9622 NEW , NIKE FREE 5.0 TR FIT 4 ATHLETIC SHOE WOMEN SIZE 8.5 , Rocket Dog Womens Jazzin Swag Cotton Fashion Sneaker- Pick SZ/Color. , NIB WOMENS STEVE MADDEN LANCER BLUSH NEOPRENE SNEAKERS SHOES SZ 6-11Bobs Sport by Skechers Ring Master Womens Black Running Sneakers Athletic Shoes , Vans Unisex Era Sneakers Brown/Blue Womens size 8.5New Nike Womens Siren Print Gray Running Shoes Size 12
"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."