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.Josef Seibel Brown Clog Leather women Shoe size 6 6.5 Mule Slide Slip On , Dana Buchman Loafer Flats Size 6 Medium Gray Tweed Fabric Tassel Easy Slip OnCrocs Womens Duet Busy Day Flat STRETCH Skimmer Women's US Sz 6 Pool BlueLatinas By V Womens Maroon Shoes 8EASY STREET SPORTSTER Slingback Comfort Croc Print Brown Loafer Sz 7 M Women's , Women's Privo Clarks Mary Jane Elastic Strappy Comfort Brown Leather Shoes-7 MWomen's Fashion Shoes Thick Bottom Canvas Shoes Breathable Casual Sport SneakersWomen's Vionic Sunset Loafers Shoe Sz 8.5M Mary Jane Walking Black Orthoheel AC8Cobb Hill Parker Tan Flats Women Size 7.5 Shoes by RockportHush Puppies Women's Miera Ackland IIV ~ Brown Leateher and Suede ~ Flats , Coleman Womens Suede Leather Camping Hiking Shoes Size 5 , REEBOK Kamikaze 1 "Irredescent~W/G size 6.5~Pink, Blk, Prpl/ PPink~ M44063NEW BALANCE 490 v2 Women US 8.5 Gray Pink Purple Athletic Running ShoesSkechers Women's sz 6.5 Leather/ Textile Plaid/Buttons Mary Jane walking shoes , Pastry-Women-High-Top-Sneakers-Glam Pie Sweet Sneaker - Size 7.5 RA 70405 EUC , Rocket Dog MAGICBC Womens Magic Beach Canvas Fashion Sneaker- Choose SZ/Color.Puma Sports Lifestyle Sneakers Walking Shoes Women's Sz 9 , BROOKS P2 Pure Drift Hot Pink Womens Athletic Shoes Sz 7EUC Womens 8.5 39 Nike Air Zoom Pegasus 34 LE Sneakers Running Shoes 883269-400 , Nike Free TR 6 TR6 Running Shoes 833413-100 White Metallic Silver Womens sz 10.5 , Carlos by Carlos Santana Women's Heidi Walking ShoeVans SK8 HI REISSUE Retro Sport Glazed Ginger Men's Shoes 7 - Women's 8.5Valentine's Day Special Golden Retriever Print Running Shoes For Women- Free ShiDC UNILITE TRAINER Womens Athletic Shoes (NEW) Ladies Girls BLACK / GLACIER BLUEunder armour Escape Reflect Athletic Shoes US 10 , STEVE MADDEN Eliass Sneakers, Silver Snakeskin, size 7NWT! Nike Women's Dual Fusion TR 3 Print $80 Size 8Nike Womens Tanjun Black Running Shoes Size 9.5 (30798) , Vans Off the Wall Surf Shoes Palisades Pink Hawaiian Floral Womens 11 FlatsSkechers Performance Women's Go Run 600 Arise Trainer Black/White Size 8.5 ,
"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."