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.Circa Moc Slip On Soft Leather Women's Shoes - 6 , Cole Haan Women’s Sling Back Flats 7.5 AA burgundy khaki canvas ballet flat shoeWomen's Black Shoes Size 8 1/2 M. , RF Room Of Fashion Zara Vegan Slip On Pointy Toe Patent Ballet Flats CORALPATENT , Easy Spirit Womens gosteady Closed Toe Mules , Bernie Mev Women's Elastic Flats Supported Heel Shoes Stretch Size 38 Gold Black , Ladies Suave leather Riptape shoe LAURA , Jellypop Women’s Green Tan Loafers 8M B89TUK BLUE BLACK PLAID CLOTH SUEDE LEATHER CREEPERS A8055 UNISEX 5 M / 7 W NOS , Sas tripad woman shoes 7.5 m brown clogs mule ORTHOPEDICRieker Ballerina Slipper Shoes Court Shoes Soft Leather Insole, Grey NEWKlogs Vida Women's Clogs Display Model Shoes Black KPR 8 MTory Burch "BEACHER" Red / Orange Cream Striped Shoes Espadrilles Women's Size 9Zee Alexis Womens Gordie Shoes Rainbow 6 MI35 Caiado Bow Tie Cut Out Ballet Flats 146, Adobe, 5 USNIB Women's Ecko Skater Flats Shoes sz 11Nike Air Max 90 Essential Womens Running Shoes Size 8NEW JCrew $148 Camille Ballet Flats in Leather Size 7 Desert PinkSkechers Women's Go Walk 4 Premier Walking Shoe, White Synthetic, 9 M US , Ecco Biom Train Natural Motion Fashion Sneakers Gray Pink Women's Size , Rocket Dog - Magic Canvas Womens Fashion Sneaker- Choose SZ/Color.Reebok Women's Work 'N Cushion 2.0 Walking Shoe , Adidas Supernova Sequence 9 Womens Running Shoes AQ3553- Blu/Sil (NEW)Lists@$120 , Converse Chuck Taylor All Star CT HI Rise XHI Women Shoes Black/White 549587fPUMA Suede Classic Women's Peach Beige/White 35546267Reebok Ventilator Black/White-Yellow-Pink-Red-Silver 1-183719 Women's SZ 7 , NIB ADIDAS WOMEN'S COURTVANTAGE ASH PINK WHITE SUEDE SHOES SIZE US 5.5 100$Nike Blazer Low SHOES SNEAKERS WOMEN'S SIZE 8 Indigo BLUE NEW , Brooks Addiction 12 Women's Running Shoes 9.5 2E 1201882E463 Ombre Blue FuchsiaAsics GT 2000 3 Women's Lightning/Hot Pink/Navy Road Running Shoes 8.5M
"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."