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.Sz 8 - Mark. by Avon Women's Black & White Flats Slip Ons Pointed ToeMERRELL Circuit MJ Black/Brown Suede Mary Jane Shoes Sz. 6.5 , Clarks Collection Black Leather Button Split Toe Loafers 60626119 Womens size 9 , Mary Pepper Red Jelly Flats Sandals Bow Sz USA 8 Halloween Dorothy Wizard Of Oz , Women's Clarks Bendables Dark Brown Leather Casual Mary Janes US 7.5 M , Brand New Womens Navy Patent COLE HAAN Nantucket Camp Moc Slip On Shoes 10BCOLE HAAN Red Suede Flats Size 7 AA Emblem Toe Low Wedge LoafersWomen's Skechers Gratis-Shake It Off - Black - New in Box!! , FILA Womens Girls Athletic Shoes Size 6 !!! BLUE PINK WHITEKaty Perry Women's The Julia Mary Jane Flat Pewter Size 7.0 , LifeStride Women's Merge Slip-On Loafer - Choose SZ/Color , Hush Puppies Women's Adia Zelder Mary Janes Dusty Blue Style HW05206-428 , Nike Ladies Hi Tops 574686-055 Purple/Gray Size 8.5 s114 , Saucony Ride Hot Pink Running Shoes Women’s Sz 9 M 8 MM Offset , Womens Puma (362409-04) Vega Ballet SL Shoes (Z1) , Skechers BOBS from Women's Bobs Sparrow-Moon Lighter Sneaker , New! Women's Skechers 11834 Encore-Golden Ticket Sneakers - Black S56Womens ADIDAS DECADE HI SLEEK W Black Trainers G46963Converse All Star Women's CT Hidden Wedge Hi Top Trainers Shoe + WinterBrooks GST Sneakers Running Woman Size 8.5 Walking Exercise , Women US Shoe Size Athletic Slip On Memory Foam Casual Lightweight Sneakers Navy , NIKE Women's Air Max Hyperagressor TB Basketball, Black/White, 7 M US , NIB VANS HADLEY CHECKERBOARD PEWTER HI SHOE GRAY WOMENS SIZE 6 , New with box puma match lo basic sports woman shoe size6NEW BALANCE WL574 Wmn's Blue / White Suede/Mesh Classic Shoes Sz7 (B7) , Vans Sk8-Hi MTE Cup Lilac Snow Leather Shoes Women’s Size 9 NewTaos Step in Time Leather Womens Shoes Suede Brown Tweed Size 9Saucony Women's Kineta Relay Denim Sneaker Blue Size 6.0 , 12004 Skechers Women's Scene Stealer Fashion Sneaker, Navy/PinkWomen New Balance 442 Sneakers Brown Size 8.5 / 40 Minimal Wear WORN ONCE ,
"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."