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.SR-80 Women Jewel Embellished Shoes Ballet Flat Soft Sole Slip On Shoe Size 6~10BELINDA Slip On Casual Party Ballet Flats Office Oxford Women's Shoes Black 6.5 , andy-05/briana-09 Bowknot New Forever Slip On Synthetic Casual Women Flats ShoesSpot On Ladies Flat Black Shoe F8531 (R12)CLARKS ARTISAN 15260 Women Black Leather Low Heel Loafers Shoe Sz 9.5 M*CLARKS* Artisan Mules Slip On Leather SHOES 2" Black Comfort Brazil Women 12 ECFranco Sarto Womens Porter Leather Closed Toe Mules, Cocco Le, Size 9.0 RLtE , NICE Women's SAS Tri-Pad Comfort Low Wedge Shoes Slip-on Loafers Black-USA-8.5 S , Merrell Alpine Moc Quilted Black Hiking Slip On Loafers Shoes Womens Size 7 MANNIE Sonya Loafer Pump Womens Beautiful Beaded- Bone Color Formal Shoes 9MPrada Womens Flats Size 36 6 Black Leather Buckle Detail Loafers DriversNew Women's Cow Leather Pointy Toe Flats Slip On Oxfords Ankle Boots Casual Shoe , NINE WEST Womens 'Saxxen' Natural Suede Pointy Toe Flats Sz 9 M - 231762 , Womens Wedge Increase Mesh Breathable Fashion Comfort Sports Casual Shoes A629 , Men's Black RJS Fuzzies Slipper Moccasins Size 7/Women's Size 9 Pre-Owned!! , Mens Slippers House Shoes Corduroy Moccasin Slip On Indoor Outdoor Comfort C , Propet Tour Walker Strap Walking Shoes - Women's 9.5 M, White/Blue , Womens Stan Smith Adidas Sneakers 6Polo Ralph Lauren Brown Tan Flannel Plaid Hi Top Pony Tennis Shoes Size 9.5 D , New Women Vans Authentic Black Skateboarding Shoes Classic Canvas size US 8 , MBT Women's 71/2 7.5 Barbara Rocker Leather Walking Sneakers Shoes Brown NEW , adidas Women's Lux Clima w Running Shoe - Choose SZ/Color , NEW BALANCE WSRMCBW Cypher Lightweight Running Shoe Black/White Sz 11 US LADIESWOMEN’S NEW BALANCE 888 RUNNING SHOES PURPLE SIZE US 6MADIDAS ARIANNA CLOUDFOAM BA8742 BLUE WHITE ORIGINALS TRAINING WOMENS SIZE 7 NWOBTretorn Women's Nylite3 Plus Fashion Sneaker Blue Suede Size 6 Brand New , Women's Nike Roshe Two Flyknit 365 Shoes NEW Blue/Grey/White/Fog, MSRP $140 , Nike Wild Trail Women's Lsr Crmsn/Plrzd Bl/Brght Grp/P Trail Running Shoe 8.5MMERRELL Women's 'Azura' Leather Hiking Shoe ~ Dark Earth Red ~ Sz 7M (37.5) , Womens Shoes Slip On Pearls Flowers Fashion Sneakers Flats Oxfords Loafers New ,
"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."