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.Sperry Top-Sider Women's Shoes Size 9 Black Glitter Loafers 9MWomen's BC Footwear Flat Satin Shoes Gold Sz 7 , WOMENS LADIES SUMMER SANDALS FLAT TOE POST HOLIDAY BEECH FLIP FLOPS SHOES SIZE , VERA WANG LAVENDER slate blue suede jeweled toe ballete flat size 7mGrasshoppers Purefit Comfort Cushion Loafers EF42590 L11-CH27 SZ 8 M BeigeNew Aerin Belnord Rount Toe Leather Flats Rosewood Sz 6.5FS/NY Women's Black Silver Leather Textured Snake Print Ballet Flat Shoe SZ 6.5DANSKO Women OLIVIA SLIP-ON Shiny Black Leather Low Loafer Shoes 36 6 MNew Sperry Jaws Sneaker size 7 - NWOTWomen's SanGreen Textile Hi Top Shoes US Size 6 , Clarks Collection Women's Slip On Comfort Shoes - Size 8M - Black SuedeECCO Women's Black Leather Slip On Bicycle Toe Loafers US Sz 10/10.5 EU Sz 41 , Unisex Cape Ribbon Black Shoes Size 7 , Vans Turquoise Yellow Tie Dye Sk8 Slim Hi Top shoes 10Mnew womens round toe slip on loafers Oxford sport shoes casual Multi Color shoesFranco Sarto Women's Dalton 2 Mule , Dr. Scholl's Anna Canvas Sneakers, Women's - Size 11 M, Charcoal/Mint , Chic Womens Slip On Shake Shoes Lady Sneakers Spring Hiking Walking Creepers NewSkechers Shape Ups Toning Sneakers Womens Sz 7 Black Wht Leather Shoes-6659 , SKECHERS Bikers - Navajo Casual Shoes, Women's Size 7.5, BlackWomen's MIA Women's Roadster Sneaker Crazy Price, Birmingham Athletic Shoes , Puma Speed 300 Ignite 3 Pink - Womens - Size 8.5 B , Saucony NIB Women's Cohesion 10 Running Shoe Grey Blue 10 Wide US New , Adidas Women's Supernova ST Athletic Running Shoes Easy Blue/White/Easy Coral , VANS Authentic Lite (Mono) Mauve/Mauve Purple UltraCush WOMEN'S 7Adidas Women ADIZERO Tempo 9 Running Training Shoes Sneakers NEW , NEW New Balance Womens Flexonic WX99WG Shoe Blue Green Nature Pattern All SizesPropet TravelFit Flat - Women's Flexible Comfort Shoe - All Colors - All Sizes , BEARPAW Women's Meadow Tall 606W Boot, Chocolate,10 M US , Asics? GEL-EXCITE 3 Run Shoes ~ Everyday T5B9N ~ Women Size 7 VERY NICE ,
"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."