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.INC International Concepts women's shoes ballet flats leather red gold size 9 M , Sam Edelman Women's Aggie Loafer Gray Size 8MTaos Soulmates Womens Shoes Size 1 Brown , Womens Havaianas Flash Urban Strappy Lightweight Sandals Beach Flip Flops , Etienne Aigner "Brigette" Black Canvas Buckle Loafer Slip Ons Women's Size 6M , Cole Haan NikeAir shoes mules waterproof 8.5B shearling lined brown patent zip , FRYE QUINCY TIE MINT SUNWASH NUBUCK 9.5M Loafers Boat Shoes Summer Fun nice , Spring Step Women's Conchetta Oxford Black 40 M US , Isola - Womens - Bricen Size: 7.5 B(M) US , PUMA PINK SHOES WOMEN'S SIZE 5 1/2Jack Rogers Tucker Glitter Slip On Sneakers, Women's Size 8M, Gold Sparkle , Clarks Womens Sz 8.5 Upper Leather Fake Snake Skin Loafers Pre-Owned S18 , Asics Gel Rapid 2 T39RQ-9090 Womens Trainers~Running~SIZE ONLY~LAST FEWhot White Women's Running Shoes Mesh Breathable Tide Low Help Casual SportsWomen's Kangaroos Lotus Shoes Sneakers Size 10 With Zip Pocket Blue & Green , NORTHSIDE Blue Water Shoes Acqua Pull On Womens Size 7M EUC , WOMENS RYKA GRAY AND PINK SNEAKERS SZ 8 , Ryka Fierce Women’s Navy Pink Slip On Comfort Training Sneakers US 9.5 M B618Skechers GoWalk Taupe Canvas Slip On Cadence Walking Sneaker 9 Sale , Adidas Courtset Womens Running Shoes Navy Casual Sneakers AW4212 sz 11 , DC Sz 10W Wms 301105 Multicolor Leather Manteca 2 Mid Se Skateboard Shoes EUC! , DC Shoes Jersey City Woman's Size 5 Silver White Candy Swirl Skate Shoes $75 , Puma Womens Faas 300 V4 WN Running Shoe Sz 6 Virtual Pink 187529 FAST!NikeiD Custom "HIP HOP" Dance Hi-Top Shoes Sneakers Size 8.5 , Salomon Climatherm Ortholite Women’s Hiking Shoes Size 8.5 , NEW CONVERSE ALLSTAR Black SEQUIN LOW TOP WOMENS Size 13 SHOES Nice Men Size 11 , Chaco Women's Hopi Hiking Boot, Fawn, Size 6.0UNDER ARMOUR Atheletic Shoes - 2 Pairs - Size 7New Balance Womens Wc896rc BrightCherry/Guava Running Shoes Size 6 (362359)Free People FP Letterman Womens Metallic Silver White Platform Sneakers $128 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."