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.Womens COLE HAAN Size 7 C Wide Brown Suede Penny Loafer ShoesBORN Mules Tan Leather Size 39 Mary Jane SlidesWOMEN'S Monet Victoria Flat Slip Ons GOLD NEW IN BOX DEFECT! SIZE 6.5 MSRP$37FIDELIO Fenja STRETCH BROWN LEATHER WALKING LOAFERS SHOES 7.5 Austrian sizeNATURALIZER N5 COMFORT LADIES CASUAL SHOES SIZE 10 M Grey GUC , Enzo Angiolini "Easeylia" Pointy Toe Suede Ballet Flats Slip Ons Shoes Size 7MWomens 7 M Sperry Top-Sider Seaside Perforated Pink Slip On Loafers Shoes , Women's 8 M Simple Black Polkadot Cream Flats A073MUNRO American Women Moc-Toe Penny Loafer Size 9.5 W Brown SuedeMUNRO American Cruise Red Woven Fabric Slip On Sneaker Shoes Size 9.5 M $165 , Easy Street Women's Charlize Ballet Flat, White, 8 M US , Tamaris Women 22134 Ballet Flats sz 37 Brown Ballerinas Leather Shoes touch itKlogs Missy Womens Clogs Shoes Display Model Leather Blue Purple Floral 6 M , Salvatore Ferragamo Women Brown Italian Croc Embossed Tassel Loafers Shoes Sz 9 , Klogs Piper Womens Clog Shoes Display Model Leather Blue Spruce Plum 7.5M , LADIES WAVES F80101 ROSE GOLD BLACK SPARKLY CASUAL SPORTS TRAINERS SIZE 3 - 8Merrell Barrado J76006 Women's Size 7 Suede Zip Up Fashion Sneaker Burgundy , Nike Hyperspike Basketball Shoes Black Synthetic Women15Medium (B, M)Sperry Top-Sider Fashion Sneakers Navy Blue Fabric Women8Medium (B, M) , Nike Poler Outdoor Stuff Camp Vibes Gray Camo Womens Sneakers Sz 9 603238-001 , Danskin Now - Women's Shape-Up Sneakers White BRAND NEW IN ORIGINAL BOX , D1147M1-400 Ryka Womens Stance SMT (8- Choose SZ/Color. , Converse Chuck Taylor All Star Ox Womens 157651F Raw Sugar Canvas Shoes Size 6 , adidas Galaxy 4 K Blue Real Purple White Kids Running Shoes Sneakers CQ1811 , New Clarks Women's Wavewalk Sneakers. Size 9 , Brand New Authentic Birkenstock Gizeh BS - Black - Women's size 7 , New Nike Womens Court Lite Purple Slate Running Shoes Size 7.5 845048-503 , Nike WOMENS Roshe One Jacquard Print 845009 400 WOMENS Knit Royal BlkEtnies Women's Scout W's Skate ShoeNIKE IZANAMI TRAINING LEATHER SNEAKERS WOMEN SHOES SIZE 8.5 -WHITE- ,
"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."