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.AMERICAN EAGLE WOMEN BALLET FLAT US SIZE M MULTI-COLOR FABRIC.Dark Brown Leather AZALEIA Low Back Slides w/Strap & Buckle 7.5 M , Dansko Black Leather Slip On Heels Shoes Women's Size 38 USstock clearance: GIRLS AND WOMEN TOE POST SUMMER POM POM SANDALS ESPEDRAILLS , Draven Mutiny Polka Dots Round Toe Women's Canvas Slip On Shoes Size 7.5 Us , Traditional Punjabi Jutti Leather Mojari Women Shoes Loafers US 5.5-7.5WOMEN'S DR SCHOOLS~METALLIC TRULY PEWTER~SLIP ON~MEMORY FOAM~CASUAL LOAFER SHOES , $60 Converse Womens Size 6 Chuck Taylor All Stars Gemma Slip On Shoes Blue Grey , Danskin Now Tranquility Womens 11 M Shoe Rocks, Good for posture, comfort SandalAmazing "CLARKS" ACTIVE AIR RED LEATHER Pumps Ballet ShoesMarc Jacobs Halsey Black Womens Shoes Size 5.5 M Flats MSRP $325Womens Loafers Real Leather Pumps Fashion New Casual British Flats Walking Shoes , Womens Adidas Energy Cloud V Black Athletic Running Sport Shoes BY1917 Size 8-11 , Tory Burch Ivory Leather Ballet Flat Shoe Size 8.5 , New Balance Women's WX855WB White/Blue Cross-Trainers 6.5M , Women's Flat Skateboard Canvas Slip On Loafers Athletic Sneakers Shoes Tboxs , Suede Unisex Slippers SZ 7/8.5 Faux Fur Lined Beige Leather/Rubber Soles NEW , Converse All Star Shoes sz 7 Womens 5 Mens White Low TopsBROOKS GHOST 4 EVOLUTION WOMEN'S RUNNING*CROSS TRAINING SHOES SZ 8.5 FAIR+ COND. , Skechers Shape Ups 11801 Toning Walking Shoes Suede Tan Brown Womens Size 8.5Retro Nike Internationalist Vintage Black Whit Womens Sneakers Sz 5.5 316374-013Nike Size 8 Running Sneakers New Womens ShoesNew Balance Women's 627 Industrial Pink Gray Steel Toe Work Shoes Sz 8.5 WID627Saucony Womens Cohesion 10 Running Shoe, S15343-3 W, Grey/Mint, 8.5 Wide.NIOB SKECHERS Women's Lifesaver 11860EW D'Lites Black White Pink Sneakers 10WGianni Bini Women's Sneaker Shoe Size 7.5 / 8.5 M Brown Fabric Glitter SneakersNew Balance Gray 6.5 Minimal Barefoot Running Athletic MinimusSTEVEN by Steve Madden Womens owen Low Top Slip On Fashion, rose gold, Size 8.5 , Skechers Go Golf Birdie Golf Shoe - Women's Size 6.5 White , Converse All Star Size 12 Women’s BLACK Sequin Low Top Sneakers ,
"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."