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.7811979 LSP30 Women's Shoes Size 7 M Brown Suede Slip On Johnston & Murphy , Joe Boxer Red Mary Jane Slides Shoes Womens Size US 5 Medium Velcro Man MadeDesign Lab Womens Ice Tan Perforated Oxfords Shoes 6 Medium (B,M) BHFO 3550CLARKS LADIES DK NAVY LEATHER CLOGS-8M-GENTLY WORN-LIGHTWEIGHT-COMFY-LIGHT WEAR , Dansko dark brown leather clog shoes vtg top strap summer Sz 39 Made in PolandCROCS Cap Toe Women's Black Gold Shimmer Band Slip On Flats Shoes Size 6 , Cole Haan Loafers Size 7.5 M Womens Brown Leather Slip On Career Comfort ShoesWhite Mountain Suede Loafers Maroon Animal Print w/ Black Patent Accents 9WDiesel Floryanne Women Ballerina Flats Pointed Toe Oxfords Casual Shoes Size 38Womens Sperry Top-Sider Angelfish 9102047 Tan Leather Boat Shoes size 7 S NarrowAGL Sttilio Giusti Leombruni Cap Toe Ballet Flats Gray Leather Shoe /9.5BOCAGE Ballerines guêtres tout cuir velours noir pointure 37 NEUF , Hudson London Callie Women's Slip On Low Heel Interwoven Leather Loafers New , Klogs Haley Display Model Shoes Distressed Leather Iron 10 M , Klogs Vanna Womens Clog Shoes Display Model Black 8.5 MCONVERSE ALL STAR WOMAN'S RARE 'FLOWERS' DOUBLE TONGUE CANVAS SNEAKERS - SZ 9 , Calvin Klein Womens Jacinta Low Top Slip On Fashion SneakersJutti Indian Handmade Women Shoes Leather Flip-Flops Mojari Ballerinas US 10 , New Butterfly Swing Shoes Women's Shape Ups Toning Fitness Sneaker High Platform , New Balance Womens Shoes WL501FCS Size 7 Green Sneakers Trainers , Spring Step Brown Sandals Women's Shoes Size 10.5 , Valentine's Day Special-Shetland Sheepdog Print Running Shoes For Women-Free Shi , adidas Women's Advantage Adapt W - Choose SZ/Color , Palladium Ladies Sneaker Shoes Pallaville Hi Extremely Lightweight! Tulip Print , Skechers Women's Synergy 2.0-Mirror Image Fashion Sneaker - Choose SZ/Color , Flojos Women's Harper Braided Flip Flop White Sandalsadidas Stan Smith - White - WomensCobb Hill Women's CBY08TP Tori-CH Tori Flat Fashion Sneakers Taupe Size 11 MNEW New Balance Wellness WW1100SB. Size US9 EU40.5Reebok Yourflex Trainette RS 4.0 Mesh Running Training Sneakers Shoes Womens 7.5 ,
"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."