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.KEEN Womens Size 5 Sienna Gray Brown Canvas Slip on Mary Jane Walking FlatsRACHEL RACHEL ROY Leather Square Ballet Flats Sz 8.5 M Shoes womensAR35 Ellie Casual Round Toe Ballet Flats 275, Black, 11 US , Anne Klein New York Slip On Shoes 6 1/2 M Metallic Brass Copper FlatsSperry Top Sider Womens Angelfish Boat Shoe size 6 Tan Leather Gold BlushSkechers Bikers Step Up Leather Mary Janes, Women's Size 7.5, BrownARAVON, ELIZABETH DRESS PUMP, WOMEN'S, US 7.5M, BROWN, SYNTHETIC, NEW/DISPLAY, , U.S. Polo Assn...... Women's Aeris-k9 Oxford, Blush, Size 10.0Pony Womens Topstar Core White Low Top Sneakers Shoes 7.5 Medium (B,M) BHFO 3120Circus by Sam Edelman Women’s Graphic Denim Blue Espadrilles Shoes Size 9 M New!NEW BELLISSIMO LENA WOMENS LEATHER COMFORT TRANSEASONAL CASUAL FLAT SHOES , Adidas Womens Running Shoes Size 9 (3143) , Uzzy La Brea Sneaker Slippers Plush Unisex Black , WOMEN'S RUNNING SHOES SAUCONY OUTDUEL - Womens SIZE 9.5 SNEAKERS 9 1/2 WOMEN !!!Converse All Star Size 5 Shoes , Dr. Scholl's Womens Abbot Palomino Suede Perf Fashion Sneaker Size 7.5 (22872)Nike Dualtone Racer Midnight Navy AA4081 400 Womens Size 8 Sneaker ShoeNew Balance Fresh Foam Vongo Running Shoes Women Size 6 , Brooks Launch3 Women Sneakers Black Blue Sport Athletic Running Shoes Size 10 B , New!! Converse All-Star Hyper Magenta Low-top Athletic Shoes!!!(5) , Athletic Works Linda Slip On Shoes Sneakers Brown Size USA 10 Eur 42 1/2 , Women's Nike Shox Remix+III Boys6Y Ample Supply And Prompt Delivery Athletic ShoesWomen's ETNIES Myra Blue White Exquisite Workmanship Flats , NIKE AIR MAX THEA KJCRD BLACK/CRMSN/WHT WOMEN SIZE 9 NEW 718646 007 , Wmns Nike Free RN Motion FK 2017 Flyknit Blue Women Running 880846-401 Sz 7.5ASICS Gel-Surveyor 5 Running Shoes-Women's size 9.5 Mint , SALE!!! NWT Women's SONOMA Goods for Life Lisbeth Ankle Boots Shoes TaupeSKECHERS WOMENS GO WALK 4 -CHERISH WIDE FIT WALKING SHOES W/GRYConverse Chuck Taylor Madison Metallic Gold Beige Leather Sneakers Shoes Sz 10NEW SKECHERS GOWALK 3 SNEAKER SHOES WOMENS 8.5 SLIP ON LOAFERS 13986 REBOOT GRAY ,
"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."