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.Annie Shoes Women's Delux W Dress Pump, Black, 7.5 W US , $59 Crocs Womens Carlie Animal Wave Mary Janes, Pink Lemonade/Bubblegum, US 6Easy Street Women's Laurel Flat, Wine Leather/Suede Leather, 6 M USAnne Klein Pink w Contrast Stitch Super Soft Leather Slide Slip On Loafers 7M , Women’s Refresh Jodi-16 Leatherette Elastic Round Toe Shoes Size 8.5 , BORN Women's red Mary Jane Size 6 /36.5 EU Very Cute Shoes , CLARKS BROWN LEATHER SLIP ON LOAFERS WALKING SHOES SIZE 9 MWomen's Autumn Oxford Brogues Tassel Slip on Flat Heels Pointed Toe Casual Shoes , Tory Burch Stardust Wool Skate Slip On BLUE OLIVE OMBRE Womens Size 8 , LADIES DOWN TO EARTH SLIP ON WEAVED ELASTICATED FLATS SHOES F80219Sanuk Women's Kat Paw TX Plaid Slip On Shoes Loafers Black Plaid Size 7NEW Womens Aetrex Brown Mary Jane Stretch Fabric/Leather Support Comfort ShoesPAIRE DE DR MARTENS POINTURE 41 OU 7 UK / BORDEAUX / BON ETATWomen's New Balance 676 Training Workout Shoes Sneaker US8 UK6 EUR39 , Fitflop Uberknit Toe-Thong Sandals US Ladies 7M BLACK SANDALS M46-001 NEW BOX , LaPlume, Paolo, Gold Metallic, Size 37 Flat, Anti-Shock SoleAdidas Silver Pink 551089 Womens Size 8.5 , Blink Womens Creepers Aztec Sneakers Shoes 39 Size 8.5 US Multi-ColorSkechers Shape Ups Metabolize 11800 Womens 9.5 White Walking Toning Sneakers , barre'letixx ELEMENT 14 Women's Barre/Yoga/Pilates shoe Slate Gray LG 8.5-11 , Womens Basketball Athletic Shoes High top Training Sports Shock Absorb Sneakers , Women's NEW BALANCE WL420DFB SNEAKERS Big Clearance Sale Athletic ShoesWMNS Nike Air Max Thea GYM RED/UNIVERSITY RED 599409 606 Running SZ 8.5 , New Olukai 20271 DEDE Pehuea Trench Blue Women's Slip On Shoes 6 USNew Nike Women's Lunar Speed 3 Tennis Shoes White/Light Blue/Gold 429999-102 , Skechers 14918W Performance Womens Go Walk 4-Gifted Sneaker- Choose SZ/Color.NIKE WOMENS SOLARSOFT MOCCASIN 622268-003 CLASSIC STONE CRYSTAL MINT DS SIZE: 7ASICS Womens Gel-Surveyor 5 Shark/Phlox/FlashCoral Running Shoes Size 8.5 , Inov-8 Race Ultra 290 Unisex Mens 9 Womens 10.5 Standard Fit Trail Running ShoesNike iD Roshe One Running Shoe iD 897153-991, Black/Grey, 8
"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."