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 Women's DANA BUCHMAN BONNIE Black Wedge Slip On Dress Shoes SZ 6.5HUSH PUPPIES The Body Shoe BLACK LEATHER LOAFERS SHOES 5 M N EUROBrand New Ladies Canvas Causal Shoes Size 5 - 10 , Aldo Leopard Print Casual Brown Boat Mokasins Loafers Size 37 Euro Flats , CUSHE Women's Graphite Leather Boardwalk Mary Jane Shoe 9 US/ 40 EUMOUNTAIN SOLE BROWN WENDA Soft Mary Jane Style Dress Shoe 9.5 M women's FlatsSperry Top-Sider Women's Blue Fish 2 Eye Leather Boat Shoes Chocolate Sz 5.5 new , Uaed Bass Weejuns Jaclyn Loafer Black Leather Tassel Kiltie Shoe Sz 9.5 M , Dr. Martens US Sz 7 Rosyna Slip On Loafers Heeled Grain Pebble Leather Black , new Women's Couples Fashion Sneakers Casual Sports Athletic Running Shoes99CAMPER WOMENS FLAT SHOES MARY JANES STYLE SIZE; US 8 , Womens Oxford Shoes Size 8 Loafer College Low Heel Dress Slip ons shoes Formal , Women's New Balance 847 V2 Running Cross Training shoes size 9.5 US , Saucony Womens - Blue Running Shoes Size 8.5 (367186) , PUMA-UNI GV SPECIAL Silhouette 34356967 BLACK- 100% Authentic New with BoxMen's Reef Phantom Prints Sandal RF2036 Black/Steel Blue 100% Original NewMens NIB HideAways Suede Moccasin Slippers Indoor-Outdoor Brown Fur-Lined 12EEE , Roxy Women's Shoreside Sport Sandal, Black, Size 10.0 N0t4Nike 6.0 Air Morgan Athletic Rainbow 318886-311 Womens Size 9 ShoesNEW Adidas Originals Women's Classic Sneakers Running Purple Pink Shoes Size 9.5Skechers D Lites Biggest Fan Sneakers-Women's size 8.5 EW BlackAsics Gt-2160 Lightning Kiwi Titanium, US Size 8.5 Women's (T154N) , Skechers 23436 Navy Air Cooled Memory Foam Slip On SneakersNike Blazer Mid Vintage Liberty OG shoes Womens New Authentic 540858-200Nike WMNS Zoom Fit PINK Training Running Shoes Sneakers 704658 008 6.5 , Original Vans 106 Vulcanized Black VN-099ZY28 Canvas Casual Women *NO BOX , *BRAND NEW* WOMEN'S SKECHERS 10 B MEDIUM M BLACK W/ MULTI-COLORED SOLE MEM. FOAM , Vans Off The Wall Blue Galaxy Sneaker Womens 10 Mens 8.5 Blue Skate Sk8 Shoe A11SKECHERS Performance Go Walk 4 Exceed Slip On - Women's Size 6.5 Gray/BlackRialto Women's Aria Slingback Nude Patent Flats ,
"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."