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 White Open Toe Flat Canvas Shoe Pump 9 $40Women's White, Pink Leather Dr. COMFORT "Susie" Mary Janes Size 8.5 N Great Con , Henry Ferrera Women's Ocean-Club 200 Slip On Loafer, Sky Blue Glitter, 8.5 B(M)Clarks Bendables 8.5 tan leather loafer sandals preowned good condition , Ralph Lauren Womens 8.5 Solid Red Patent Leather Round Toe Slip On Ballet Flat , WOMEN'S MERRELL PLAZA BANDEAU BLACK LEATHER MARY JANE CASUAL COMFORT SHOES 7.5 , Dexflex Womens Size 10 Chevron Print Woven Ballet Flats 165876 Comfort , ROCKPORT Casual Suede Leather Loafers Slip-on Mocs Shoes -Woman's US 6.5M , Skechers BOBS Women's Bobs Plush-Star Struck Ankle Bootie Black 5 M USIsaac Mizrahi Women's Mint Colored Flats 5**A2 by Aerosoles Fast Ride Loafers, Women's Size 6 M, Black , J Slides Aztec Casual Slip On Shoes - Women's Size 6, Sand Suede , naturalizer Emiline Classic Slip On Loafers, Rose Gold MetallicASICS GEL GALAXY 5 T281N Size: 9 RUNNING JOGGING WALKING VERY COMFORTABLE SHOES , Women 2018 Slip On Flats Floral Loafers Sneakers Athletic Shoes Leisure NewDansko Roxy Burgundy Leather Croco Embossed Mary Janes (38) 7.5 - 8 M Enjoy , Brand New!| Nautical Themed| Women's Original KEDS Tennis Sneakers| Size 9.5 US , LOHAS Indoor Faux Leather Comfort Warm Sandals Slippers Slides - men,gray+blackMENS GROSBY ANTON COMFORTABLE KHAKI BROWN SLIPPERS MOCCASINS SHOES SIZE 6-12Rhinestone Side Zip Women’s Sneakers Olive Size 7Reebok Sublite Women US 9 Black White + Pink Athletic Running Shoes , Women's VICTORIA Sneaker 112558 Gris Paillettes Finely Processed Athletic Shoes , Skechers Shape Ups Black White Gray Size 9 Walking Shoes Sneakers Toning , Puma Women's Faas 550 NM Running Shoe - Vivid Blue/White (18629-04)Nike Air Huarache Run Premium Platinum/Grey-Anthracite-Silver 683818-009 SZ 9.5 , Nike Free TR 6 Print Black White Cool Grey running training 833424-001 Size 9.5 , COLE HAAN Snake Skin Beige Tan Black Slides Sneakers Women Size 10 BCasual Womens Hidden Wedge Heels Pointy Toe Sneaker Shoes Athletic Real Leather , Keds Women's Champion Slip Breton Stripe Jute Fashion Sneaker - Choose SZ/ColorSkechers Women's You-14960 Sneaker - Choose SZ/Color
"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."