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.Easy Street Charlize Cutout Ballet Flats 706, Bronze, 8 USLands End Women’s Size 7 Leopard Calf Hair Leather Loafers Flats Pink Scallops , White Mountain Women's Pink Bow Clogs Shoes Leather Women's Size 7M , USED MERRELL PIROUETTE LEATHER BROWN GOLD WOMENS US 10 J76430 , Paul Green Size 5 (Women’s US 7.5 M) Black Leather Stretchy Sneaker Loafer SlipNine West Benna 8 M Dark Natural Beige Suede Leather Flats Ballet Slip on PumpsJOE N JOYCE Bilbao Espadrilles - Blue - TextileECCO LADIES CAMEL LEATHER ATHLETIC DRIVING OXFORD SIZE 5.5 M /Dansko Burgundy Solstice Monk Slip On Clog Womens Sz 41 Clogs Shoes Black CherryCLARKS Ballerines Cuir Ajouré Bicolore Petits Talons T 4.5 UK / T 37.5 TTBE , 8 | Merrell Jungle Moc Women Gunsmoke Suede Leather Slip On Flat Comrort MocMerrell Dassie Fold Slide Clogs, Women's Size 9.5, BlackSperry Top-Sider Intrepid Womens Plaid/Dark Tan Boat Shoes , Cole Haan Pinch Weekender Loafer - Women's Size 8.5 B, GoldNEW IN BOX WOMENS REEBOK CROSSFIT NANO 7.0 SNEAKERS BD5120-SIZE 9.5Nike SB Stefan Janoski grey suede low-top sneakers skate shoes - , Zoot ~ Women's Woman's Tempo Trainer Running Shoes ~ Size 8New Dearfoams Men's Microsuede Clog Slippers with Memory FoamMAZUNO "WAVE RALLY 5" VOLLYBALL/ATHLETIC........SIZE: 8......VERY GOOD CONDITION , NIKE WOMENS KAWA SLIDE 834588 101 SIZES 6-11 Free Shipping , Classic White Canvas Low Top Converse Chuck Taylor All Star Women’s Size 6 1/2 , Mustang By MTNG Womens 55638 Low Top Sneaker Shoes , Women's Aetrex Shoes Modern Techniques FlatsGola Classics Coaster Lizard Women's Metallic Animal Print Leather Trainers NewNike Size 8 Running Sneakers New Womens Shoes , Women's Brooks Transcend 5 size 11Skechers Women's Gratis - Cozy N' Carefree Sneaker, , Pearl Izumi Womens W X-Road Fuel Iv AquaMint Cycling Cleats Size 11 (351834) , Nike Studio Wrap 4 Women's Training Shoes Yoga Dance Black 811650 001 Size 5 , New Nine West Womens 25024568 Silver/Black Fashion Sneaker Size 8.5
"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."