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.JOSEF SEIBEL ~HUNGARY~ BROWN CROC PATENT LEATHER WEDGE LOAFERS ~ 39 H /8 US , Privo By Clarks Brown Suede Slip On Maryjanes Size 6M Casual Comfort ShoesWomens Black Glitter Round Toe Sexy Ballet Flats Size 11Ladies sparkly flat party shoes with large jewel bow to front , Fitflop Superskate Suede Tassel Shoes Size 7.5 , NWT! ANNIE SHANELL Slip On Women's Pink Pumps Shoe Size 8 WWFisca Lady Pebbled Leather Drivers Casual Flat Loafer Shoes with Breathable... , Nine West Onika Embroidered d'Orsay Flats, Women's - Size 7 M, BlackJoseph Seibel Women's 38/7.5 Light Brown Spirit Of Nature Leather Sneakers 218Ecco Blue Loafers Womens Sz 38 Medium Suede Low heel , Skechers Go Walk Sport Supreme Women's All Plain Black Slip On Work Loafers NewPrivo burgundy and orange slides - womens 9 M , Flat Shoes Women Autumn Slip On Shoes For Women Loafers Moccasin Womens Zapatos , Womens Cole Hann Tan and Green Slip On Mules Women's Size 7M.Wolky Ojibwa Red Italian Softy Leather Shoe US 6.5/7Klogs Natalie Women's Clogs Display Model Shoes Yankee Orleans Navy 9.5 W , Klogs Aubrey Womens Clogs Display Model Shoes Black Snake 9.5 MRALPH LAUREN Brooke Monogram Logo Loafers SlipOn Leather Brown Shoes 7.5AA , NEW, NIKE WOMAN'S GOLF SUEDE SHOES VINTAGE 192010 221 00 SIZE 8 MLeather Women Square Toe Oxfords Rivet Motor Decor Slip On Loafer New Flat ShoesMens Natural Felt Virgin Wool Slippers Shoes Mule Size / , Asics Gel QuickWalk Running Shoes Womens Sneakers Sz US 7.5 Silver & Pink , SNEACKERS TENNIS TOILE ET CORDE 40 FEMME KAKI ECRUSkechers RELAXED FIT Womens Sz 5M Black Memory Foam Slip-On Walking Shoes , Women's Donald J Pliner Sport-I-Que Economy FlatsConverse John Varvatos Chuck Taylor All Star 2 Black/White 153887C Retail $170 , New Balance 999 Dark Gray Lifestyle Ladies Running Sneakers Size 7,New w/ Box , Puma Fierce Quilted Slip On Grey Textile Womens Trainers 189418 02 M16 , Women's SKECHERS 11624R GYHP BRAVOS Photo Finish Shoes Sneakers Gray- Pink New , Asics Gel Women's Running Shoes Size 11 US ,EUR SIZE 43.5 Pink/Neon Green
"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."