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.NEW Womens MIA GIRL MESSI Black Slip On Flats Loafers Dress Shoes SZ 7Emporio Naka Sao Paulo Womens Mary Jane Shoes Black Leather Size 6.5 - 7 / 37Aetrax Brown Croc Pebble Leather Mary Janes Comfort Shoes Size 8.5MButterfly Twists Samantha Glitter Folding Flat Ballerinas Bronze Women’s Size 7 , Bobs from Sketchers Memory Foam Arch Pillow Womens Gray Loafers Sz 11 , Women's Skechers 31232/NTMT Keepsakes High- Party Pause Nat/Multi 8.5Cute Adorable Stylish Ellie Shoes Pink Criss Cross Peep Toe Flats Adult Women , Cole Haan Ballet Flats Size 8.5 Faux Snake Print Skin Slip-on Shoes , Cole Haan Tali Beige Leather Women’s Ballet Flats MSRP $178 US 10.5 AA B695 , Klogs Missy Women's Clog Shoes Display Model Castle 7 MCircus By Sam Edelman 7 M Womens Scotlyn Grey Frost And Black Lot Of 2 SneakersBABY PHAT SHOES WOMEN'S SIZE 7 1/2Vince Camuto Womens bayana Leather Low Top Slip On Fashion, Black, Size 8.0 OlOnSperry Top-Sider Shoes 8 M 8M Brown Women's Suede Leather Tassels Non-Marking , Ladies Mesh Holes Rhinestones Breathable Sneakers Shoes Sports Hidden Wedge PumpNew Balance WR768ST Women Blue White Athletic Running Shoe Size 7.5M Pre OwnedSkecher Sport Energy Optimum Casual, White, Leather,Women's US 7.5 , New Balance 928 Women's Health Walking Fitness Sneakers White Size 7 EEEE E2 , Women's New Balance WXC5000G Multicolor Country Spike Shoe Size 6.5 MJUAN Walking Shoes Fitness Shoes Exercise Shoes Sports Shoes Mesh Running Sho...Jack Purcell Converse Women 8.5 Red Polka Dot Canvas Low Profile SneakersWomen's Authentic Prada Black Leather Elastic Slip-On Sneakers, size 35.5Nike Air Zoom Pegasus 32 Print 806806-308 Voltage Green/Hyper Orange/White SZ 10 , Bm Catwalk Light Jeans Slip-On Women's Shoes Size , CONVERSE ALL STARS Unisex tropical sneakers/ NEW. 9 , Saucony Ride 9 Running Shoes - Women's Size 10.5, Purple/Blue/Mint , NIKE AIR KAISHI WOMENS TRAINERS SIZE 3 to 8 ANTHRACITE RUNNING SHOES NEW LIGHT , Nike LD Runner LW PREM Womens Shoes Pure Platinium Ivoire Sz 7 New , Ladies Tennis Pink Size 9 Medium New , Ladies Caterpillar Leather Trainers In Bronze And Pink 'Sly'
"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."