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.Womens Slip Trainers Shoes Flats Plimsoll Classic On Sneakers Loafer Pumps UK3-8Ladies Spot On Black Slip On Ballerina Shoes Woven Detail & Bow Trim F8776 WQUPID ~ OXFORD STYLE ~ NUBUCK TYPE FINISH ~ BURNISH FINISH (DISTRESSED) ~ SHOES , Aldo Women's Afaossi Fashion Sneaker, Black Synthetic, ZIPPER [SZ 7.5 M] D8590Vionic Orthaheel Pink Suede Kiltie Petaluma Orthotic Mocassin Loafer 5 NEW , Stuart Weitzman 5.5 Gray Wool Buckle Square Toe Slip On Career Flats Shoes PumpsARRAY Womens Freedom Leather Square Toe Loafers, Navy, Size 8.0 0khb , Vaneli Womens Aimee Loafer- Pick SZ/Color.Easy Spirit Kable Slip On Low Wegde Flats 601, Black/Black, 8.5 US , Vionic Orthaheel Technology Palermo Bronze Snake Sneakers Women's 10EASY SPIRIT Ladies' Size 6.5 CASUAL ATHLETIC SHOES (Pewter/Gold; Anti-Gravity)Ladies MUNRO AMERICAN two tone walking wedge leather zip front USA made 9.5 MSperry Women's "7 Seas" Boat Shoes White 9.5 MZumba Energy Fuze Shoes - Graphite/Yellow(Green) , ASICS GEL-SONOMA 3 WOMENS Running Shoe Sz 11 NEARLY NEW , New Balance JoJo Slide Women's Sandal, Grey-pink, Size 7.0 grBU , ASICS GT-2000 Women's Running Shoes Black Blue Pink Athletic Sneakers Size 8Superga Black Velvet Sneakers w Size 9.5 New Without tagsNew Balance W560v6 Running Shoes - Women's Size 9.5B, Grey/TealASICS Gel-Exalt 3 Running Shoe - Women's Size 6.5, Navy/Purple/Silver , New Kenneth Cole Womens Kam-Era Cloud/Embossed Fashion Shoes Size 9.5 , Skechers 49336 Womens Bikers Curbed Fashion Sneaker- Choose SZ/Color. , WOMEN'S/JUNIOR SHOES SNEAKERS ADIDAS CF RACER TR K [DB1868]WMNS Nike Air Jordan 1 Retro Low NS SZ 8.5 White Metallic Gold AH7232-100Tretorn Men's NYLITEPLUS Sneaker, Vintage White/Night, 10.5 Medium US , Puma Woman Knockout Bright Pink High Top Gym Shoes Sneakers w Soft Foam insole 9New Womens Teva Ewaso Blue Waterproof Trail Hiking Sport Outdoor Camping Shoes , NWT WOMENS NIKE FS LITE RUN 3 PRINT TRAINING RUNNING SHOES SZ 6 , Keen Presidio Walking Shoes, Women's - Size 8.5, Cascade Brown , NWT Skechers Ladies Go Step Lite Slip On Shoe Gray Walking Comfort Size (7)W@W
"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."