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.Dark Brown W/Appliqued Pattern PILAO by J. GEAN Low Slip On Shoes US 8 , Pierre Dumas Womens Shoes NEW $45 Driving Turquoise Perf Loafer Driver 6 M , Aerosoles Women's You Betcha Slip-on Loafer, Dark Pink Nubuck, 7.5 W US , Yellow Box Women's Size 6 Shoes Flip Flops Silver Sparkle , KEDS BRAND BROWN FABRIC SLIP ON FAUX FUR LINING SIZE 7.5M SHOES EUCVintage Lime Neon Green Flats Size 7.5 , Women's Croft & Barrow Open toe Slides Black Uppers Size 11 M Excellent ConditiWomens Shoes Nine West Speakup Flats Loafers Bee Tapestry Red/Gray Size 7COLE HAAN AIR WOMENS GOLD FLATS LOAFERS SZ 6.5 TASSEL LEATHER EUC , WOMEN'S NINE WEST SNAKE SKIN PRINT FLATS ROUND TOE SHOES GRAY SizE 8.5 M , BALLY Grimsela Brown Leather Nubuck Boat Shoes Womens 6.5 Moccasin Toe Loafers , Sperry Top-Sider Angelfish $90 Women's Boat Shoes Size 8.5 Floral Leather BeigeHush Puppies Women’s Sz 8 Brown Leather Moccasin Flats ShoesDancing Days Flamingo Vintage Rockabilly Retro Ballerina Pointed Pump Flat ShoesAriat T Strap Sandals Shalimar II Red Womens 9.5 Shoes 10011008 Retail $119 , Women's Merrell Women's Primo Breeze II Size 6 10A , Skechers Serrano Women Size 8.5 Brown Leather Suede Casual SneakersAsics GEL-Kayano 22 Lite-Show Women's Pink Aqua-Splash Running Shoes Size 9 , BOBS from Skechers Women's Luxe BOBS-Dazzlin Ballet Flat , Merrell OrthoLite Women's Brown Leather Slip On Plaza Ballet Flat Clogs Size 9.5Converse All Star Low Top Canvas Shoes Magenta Women’s Size 9 , Women's Softspots Shoes Size 10 Quality Primacy FlatsLadies Skechers Go Walk Lite SHANTI Fashion Trainers Casual Soft BreathableConverse Chuck Taylor All Star Hi Black/White (WS) (555966C)Women's Nike REAX Run 7 Shoes Black White Fireberry Running Sneaker (7)Women's Skechers EZ FLEX 3.0 SONGFUL 23435/BRN Brown Brand New , CONVERSE CT HI Tattoo Canvas White Trainers 145643CSkechers Women's Go Walk 4-Attuned Sneaker , NEW VANS PALISADES SF JUST STRIPES DRIZZLE WOMENS 5 NIBnike shox silver pink Running Shoes size 6 ,
"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."