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.Womens Block Heels Ankle Strap Sandals Girl's Casual Low Top Shoes Oxfords Round , IKRUSH Womens Alex Slip On Chunky Glitter Trainers , FootzyFolds - Cora Sheer - Sandals - BLACK 6 M or 8 M USPALLADIUM - Women's 2 TONE BROWN LEATHER MARY JANE FLATS SHOES -- SIZE 7 USIndigo Rd. Womens Bow Loafers Color Nude Size 6 , Kathy VanZeeland Ballerina Flats Charm Embellished Orchid Size 9 WideUnRestricted Womens Red White Striped Cut Out Tie Flats Size 7ZARA Satin HighHeel Sandals Pink Brooch US//37; 7.5/38; 8/39; 9/40; 10/41 , Cole Haan 9.5B Women Flats Shoes Tan & Cream LeatherWalking Cradles Women's Flounce Boat Shoe, Black Leater, 6.5 M USKEEN SAMPLE 100623 WOMENS DELANCEY MARY JANE CNX LEATHER SHOES US 7,MISMATCHED NEW Women's KEDS PACER WH14408 LEFT SZ 7.5 RIGHT SZ 7 Shoes , Fashion Women's Running Shoes Casual Shoes Walking Sneakers Outdoor SneakersSkechers Bikers Provocative Shoes Womens Casual Shoes , womens size 11 asics gel gt-2000 running walking , CONVERSE All-Stars Neon yellow green volt black Shoes 153919F Womens 13 Mens 11 , WOMENS SKECHERS Silver Gray Purple Leather Tennis Shoe SN 12229 US Size 8.5Women's Adidas Blades Sneakers Size us -7.5- B PRE-OWNED , CONVERSE ONE STAR ATHLETIC SHOES / MULTI COLOR ( SIZE 11 ) WOMEN’S , PUMA Women's Tazon 6 Knit Wn White Silver 7.5 M US , Easy Spirit Women's Getflex Slip On Navy/Navy Fabric Flats , WOMEN'S SHOES SNEAKERS ADIDAS CLOUDFOAM ADVANTAGE [AW3977] , NEW BALANCE 300 Sz 4.5Y (6 women's) Rev Lite CRT300FM , New Balance Vazee Breathe V1 Women's Competition Running Shoes WBREAHT SIZE 11WASH BOWIE WEDGE SIZE 39 US 8 BURGUNDY SUEDE ADJUSTABLE STRAP SNEAKER BOOT A9Vans Black Canvas Shoes UA Court Mid Womens size 8.5 NewNIKE WOMEN'S DUNK LOW TOP SB TENNIS SHOES MINT GREEN MAROON SIZE 8 , Nike Dual Fusion Hills Mid LTR Womens 9M Hiking Boots Deep Royal Blue Hyper PinkMint ASICS GEL-CUMULUS 17 2016 Womens 11 43 EUR Silver turquoise pinkMerrell Women’s 6.5 ProTerra VIM Sport Hiking Shoes Aluminum J57254
"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."