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.New Womens Fringe Front Bow Fur Lining Bow Moccasin Oxford Loafer Slipper Shoes , Hurley ‘Wrapsody’ Beige Pink Ballerina Ankle Ribbon Tie Flats Size 8 , Annie Comfort Erin Faux Suede Flats - Women's Size 6.5 M, Black , CLARKS COLLECTION 26104787 Wo's 8M Gray SuedeFlats Slip Ons Elastic StrapEasy Spirit Women's Grey/Blue Leather Suede Oxford Casual Shoes Size US 9.5 BVivienne Westwood Melissa Ultragirl Flat Shoes Gold Bow Peep Toe Women’s Sz 37 , Cole Haan Air US 8.5B Metallic Silver Ballet FlatsCOBB HILL by New Balance Womens Burgundy Leather Loafer Twist Size 8M , FS/NY Black Leather Snake Skin Print Wedge Slip On Women's Shoes Sz 6Madewell Pointy Toe Black Suede Gold Dot Ankle Flats with Ankle Strap Size 10 , SAS Women's Penny Loafers Metallic Gold Leather Moc Toe Comfort Shoes Size 10 NYves Saint Laurent Sz 7.5 Brown Suede Pumps Crisscross Straps Low Heel Italy YSL , Klogs Marisa Womens Clog Shoes Display Model White 8 M , Aravon Women's Delilah Flat, Stone, 10 D , BX698 SARA LOPEZ shoes black leather women moccasins , VANS Authentic Original Low Top Exclusive Neon Hot Pink Black TB9C sz 6 womens , Merrell Mesa Ventilator II Taupe Suede Hiking Trail Shoes Women's Size 9 m , NYX-01-34 WOMEN STRETCH KNIT HIGH BOOTIE J’S AWAKE OLIVE , Flossy Gallur Women's Classic Casual Summer Slip-On Espadrilles Plimsols NavyCurves Cross trainers Women’s Sz 9 Leather Sneaker Shoe Purple/White BRAND NEW , Womens High Top Hidden Wedge Round Toe Sneakers Trainers Mixed Colors Shoes C398 , ASICS GEL SCRAM 3 WOMEN'S TRAIL RUNNING SHOES US SIZE 11 VGPC! , Women's SUBLIMES BALLERINES CASTANER T.36.5 NEUVES!!!!!! To Win A High Admiration And Is Widely Trusted At Home And Abroad FlatsNew Nike Womens Kaishi Run Black 654845 011 , Adidas Women Running Shoes Galaxy 4 Training Fashion CP8837 Fitness New Gym , adidas Gazelle Stitch and Turn Shoes Sneaker Wonder Pink bb6708 8.5Reebok Classic Sneakers Shoes Womens 6.5 White High Top Princess Shoes Straps , New New Balance Womens Wt910ta2 Green/Pink Running Shoes Size 5 (C,D,W)Skechers Black Suede Rhinestones Dazzle'em Slip-On Platform Sneakers 9 SaleLSGEGO Women's Breathable Running Shoes Air Cushion Athletic Jogging Sneakers BM
"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."