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.Cole haan Women's Pinch Weekender Camp Moc BeigeW02517 Size 6.5 BPink Floral Ballet Flats womens size 9 NWTCO OP Barneys New York Black Patent Leather Pointed Toe Flat Shoes Size 35, 5 , NIB FERGALICIOUS "ALISHA" TAN CUTOUT BALLET FLATS SHOES (left 6, right 6 1/2)LLBean Signature Women's Slip-Ons shoes/sneakers size 7 M | 50% Off , Ara Green Gray Square Toe Animal Print Loafers Size 6SAS FREE TIME TRIPAD COMFORT WOMENS WHITE LEATHER SHOES SIZE 11.5 N , universal thread women's shoes size 11 , Easy Spirit Women's Kalindi D'Orsay Flats, Natural Combo, 7.5 MWomen’s Dansko Mary Jane Shoes Leather Brown Size 40 (9.5-10) , Black Leather DANSKO Stapled CLogs US 7.5 - 8 , Aetrex Ambulator 1260 Women's Double Strap Black Walking Shoe , Sperry Top-Sider Women's SB870 White Sneaker , Pony Womens Topstar Core White Low Top Sneakers Shoes 7.5 Medium (B,M) BHFO 3154Jon Josef Women's Ballet Flat Paloma's Espadrilles Patent Size 6 M USMerrell Womens Shoes 6 Primo Patch Bug Brown Leather Suede Slip On Loafers Moc , Clarks Bendables Brown Leather Suede Mules Loafers Clogs Block Heel Boho Sz 9NIKE REVOLUTION 2 TRAINING RUNNING SHOES / MULTI COLOR ( SIZE 6.5 ) WOMEN’S , LL Bean Womens 7M Gray Oroke Stitching Mary Janes Mesh Athletic Shoes Y443Burnetie Women's High TopWomen's BROOKS Pure Grit 2 Running Shoes Size 9.5 B , Women's Mizuno Wave Inspire 9 Shoes Sneaker Size 6.5 Running Black Gray Teal AC2Classic Women’s Chic Sweet Bowknot Wedge Platform Creepy Sneaker Shoes Plus Size , New Puma 364092 02 Basket Platform VR Puma Black Women's Casual Shoes 8.5 USYRU Black and white platform Prizm Sandals , 599432 004 NIKE ROSHE ONE RUN SAFARI PRINT COOL GREY RUNNING SHOES 11 WOMENS , NIKE AIR PEGASUS GX POWDER BLUE MIDNIGHT NAVY RUNNING WOMENS SZ 6-7 324853-441New Balance 1260v6 Women's Stability Runing Shoes Size 9.5 , Converse Chuck Taylor All-Star Women's Dainty Xhi Chestnut 6.5 , Nike 806559-401 Zoom Rival Track Racing Shoes Baby Blue Womens 9 ,
"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."