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.Clarks Metallic Women's Patent Leather Ballet Flats Size Size 8M 8 MWomen’s 7½M Clarks Loafers Red leather Slip-on 1½” Heels Brazil Excellent Cond. , ROCKPORT BLUE SHOES WOMENS SIZE 8 Mlucky brand leather flats new without box tan size 7.5Dexter Shoes Gray Suede Slip On Womens Size 6MLADIES SPOT ON LIGHT PURPLE FLAT SHOE WITH BOW "F8670"Pink Shoes FADED GLORY Knit Fabric Ballet Flats Size 9 Fabric Uppers , SPERRY Top-Sider Women Navy Blue Green Leather Nautical Slip On Boat Shoes 12MEarthies Vanya Floral Slip On Women's Size 8 , Women's BORN CROWN Hand Crafted Footwear Leather Clogs Shoes Size 10 (42) Brown , Bernie Mev Womens Rigged Becca Light Gold Mary Jane Size 8 , ELLE BEIGE TAN GENUINE LEATHER FLAT WOMEN'S SANDALS MULES SHOES SIZE 8 , ENZO ANGIOLINI Liberty Leather patent leather Flats loafers Size 8 N white , Dansko Brittany Clogs - Women's Size 9.5, BlackMerrell Dassie Fold Moc Loafer - Women's Size 10 M - BlackSperry Women's Metallic Tipped Authentic Original 2-Eye Boat Shoe - 9265604*Katy Perry Women's The Julia Mary Jane Flat, Pewter, Size 7.0 , Brooks HFST Running Shoes Size 7NATIVE "JERICHO" FLATS - NWT - SIZE AUS 8 - RRP $145.00 - VEGAN FRIENDLYBearpaw Men's Ori Scuff Slipper Gray II Cow Suede Size 10 MSuperga Loafer Slip On Sneaker Deck Shoe US 9.5 Canvas Gray S007WA0Fashion Galaxy Women's Running Shoes Breathabl Sport Shoes Ultra-Light SneakerNew Womens Shoes Fashion Sneakers Sport Ankle Boots Platform Wedges High Heels , Fila Women's BBN 84 Ice Walking Shoe - Choose SZ/ColorSkechers Womens - Gray Running Shoes Size 9.5 (368237)Women's Nike Air Zoom Wildhorse 3 Sneakers, Black/Turquoise/Orange, Size: 6.5 , Converse One Star 3V Strap OX Pink White Kids Youth Women Shoes Sneakers 660038C , Reebok Women BS9987 Trainfusion nine Training shoes black white silver sneakers , Joie Kidmore Black Sport Mesh, Size 11 US / 41 $190.00Saucony GRID COHESION 10 Womens Grey/Black/Coral S15333-14 Running Shoes
"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."