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.B0BS WOMENS RED AND TWEED SLIP ON SHOES SIZE 8 , BELLINI WOMEN'S SIZE 9 BROWN SLIP-ON FLATS LOAFERS LEATHER GOLD HORSE-BIT OXFORD , SAS Womens 9.5 W Roamer Black Mary Jane Tripad Comfort Shoes USA , MUNRO American Women's Black Leather Slip On Loafers Shoes Size 8.5 NFranco Sarto Women's Black Leather Flats 5 M , Keds Checkered Plaid Corduroy Black White Mules Slides Sneakers 8.5 , ABIGALEll Womans 11B Blue denim chestnut brown ballet flat slip on buckle shoe , Clarks Size 8 Bendables Patent Animal Print Brown Loafers Shoes Alligator 011BIRKENSTOCK BIRKI'S ANIMAL FUR PRINT SHOES SIZE 38 EXCELLENT MUST SEE! , Keen Women's Multicolor Size 7 Slip On Mary Jane Shoes$145 VIA SPIGA KEEPER Camel SOFT Leather Designer Comfort Pumps 7 RUN SMALLKravings by Klogs Womens ASTORIA Shoes Display Model Black 8 MCole Haan Country Black Suede Slip-On Casual Dress Work Women's Shoes SZ 8.5 B , Womens Mesh Running Shoes Sport Sneakers Athletic Casual Outdoor Trainers Casual , B. O. C. by Born Binta flats grey lizzard 6.5 Med NEW , 116))SAS Shoes Black Mary Jane Flats Tripad Comfort Women’s Sz. 9.5 N. *MUC*RYKA ~ NEW $87 BROWN SUEDE LEATHER ATHLETIC SHOES SNEAKERS MULES 7 W NEW NIB , Woolrich Chatham Run Fleece Slippers - Men's Size 11, Red/BlackWinter Men Fleece Warm Soft Plush Skidproof Indoor Household Slippers Shoes Hot , L.L. Bean women's size 7 Sneakers On Pink Leather Mesh Shoes style 05330 z1 , Columbia Black Audacity Plus Mary Jane Shoes Sz 8.5MPuma Womens Suede Heart Reset Blue Fashion Sneakers 8 Medium (B,M) BHFO 5721Merrell Vapor Vibram Gray Knit Women Barefoot Slip On Comfort Shoes Size US 7.5PUMA Women's Mega Nrgy Wn Sneaker - Choose SZ/Color , Asics GT-2000 4 Sneaker - Women's Size 8, Pink/BlueShoes Lotto Leggenda Iris II Lf Amf W s8160 Sneakers Woman Running Sport Blue Av , Nike Flex Experience RN 6 PREM Women's Running Shoe 881804-400 Size 10WPBP-7A Puma Caroline Women's Fashion Sneakers, Size 7M USNEW Womens 9 NIKE Zoom Rival MD 7 Pink Orange Mid Distance Track Spikes Shoes , SKECHERS EZ FLEX MELODY MAKER FOR WOMEN LADIES SIZE 5 GRAY AND ORANGE ,
"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."