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.Women's Sperry Top-Sider Bluefish 2-Eye Boat Shoe Zebra Sequins Size 5.5 MSam Edelman Nerah Sneakers Size 5 Bright Blue Slip On Platform Shoes Stretchgloria-33 New Fashion Nubuck Slip On Casual Women Flats Women Shoes Blue 10COMFORTVIEW BROWN PATENT CRICODILE EMBOSSEDLOAFERS SIZE 10 W , Primigi Sneakers Xena 39N L 8 Multi Silver , EARTH SPIRIT - 6.5, 7, 7.5 FREE SHIPPING-LADIES-CONTOURED-CUSHIONED-SHOES-BLUESeven 7 Footwear Cape Verde Coral Size 7 Women's Shoes-SHIPS N 24 HOURS , Keen size 38.5 8M Gray Green Mary Janes womens flats shoes XT 0107 , Ladies Havaianas Top Rubber Casual Slip On Sandals Brasil Flip Flops All SizesLA SCARPA PARIS FAUX SNAKE SKIN BALLERINA SHOES 40/8 1/2 NEVER WORNSperry LIMITED EDITION 18K Gold Cup A/O Boat Shoes Sz 9.5 Black Patent LambskinNew Women's Skechers 31300 Bobs Alpine Black Diamond Cool Weather Shoes Sz 7 L22Easy Street Purpose Slip-On Flats, Navywomens Floral Layers slip on oxfordplatform Round Toe loafer creeper shoes SizeVINCE CAMUTO FUSHIA PINK LEATHER BALLET FLAT SLIP ON COMFY SHOES~6.5 / 36.5 , Tony Little Cheeks Fit Body Ankle Sneaker Boot - Gray US 9.5 , VANS SIZE 8.5M MENS GENTLY USED VN-0DE1 WHITE CASUAL WALKING SHOES EURO 41 , Steve Madden Gracy Faux Suede Slip On Sneakers, Women's Size 8, Light GreyDerek Lam Shoes Crosby Black Leather High Top Janel Sneakers , Skechers Sport Woman's Size 6 Sneaker Shoe Gray Black Shoe 91320M , Kendall + Kylie Womens Reign 2 Leather Textured Fashion Sneakers Shoes BHFO 4335?Nike Juvenate Woven ?833824-301 ?Clear Jade ?Size 7 , Therafit Women's Tammy Slip On , Clarks Outdoor Womens Rock Training Purple Black Nubuck Shoes size 7 M , Saucony Women's ProGrid Integrity ST2 Walking Shoe,BlackGrey,6.5 D USWOMENS FOOTJOY EUROPA COLLECTION GOLF SHOE SIZE 5.5 M TAUPE WHITE NWOT , Adidas Womens Cloudfoam Qt Racer MysteryBlue/White/GlowOrange Running ShoesNew Balance Womens - Gray Running Shoes Size 12 (C,D,W) (362298) , Kenneth Cole Women's Kingfree Leather Sneakers, White, Size 9.5 Med. , PUMA 362223-01: Women's Suede Platform Core Fashion Sneaker, Puma Black/Puma ,
"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."