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.SAS TRIPAD Women’s Size 10 1/2 Wide Ankle Strap Open Toe Comfort Sandals , Cushe Re Treat Ballet Flats Womens Size 8 39 Purple Vegan Casual Comfort ShoesEtienne Aigner Shoes Women’s 7M Brown Slip-onsAmerican Eagle Women's Dark Brown Casual Leather Oxfords Shoes Size US W 7New Women's Ladies Slip On Flats Pumps Plimsolls Sneakers Skater Trainers Shoes , CC Resorts Sapphire Womens Casual Comfort Shoes/Flats Memory Foam/LightweightTraditional Bridal Flip-Flops Jutti Oxfords Women Leather Shoes US 7 , Rockport Moc Toe Loafer Women size 7.5 Tan Leather , Clarks Ladies 7 Burgundy Leather Mules 2”heel. Nearly New , Skechers Womens Blue Slip On Boat Shoes Size 7.5 M , Sas Womans Flats Size 8.5 N Burgundy Leather Kiltie Slip On LoafersAGL Attilio Giusti Leombruni Ballerina Flat Shoe Brown 5.5 35.5 $310 Italy FBB , J Crew Emma Crackled Metallic Leather Ballet Flats - size 8.5 - Metallic Gold , Remonte Ladies Slip On Shoes D1902 , Avia Burst Running Shoes Sneakers Lightweight Women’s Size 6.5 Blue & Lime GreenWomen's Reebok Zig Tech Shark Running Shoes Size 8 Black and Hot Pink , CONVERSE LADIES CHUCK TAYLOR HI CHILLI PEPPER RED 139841F , New Womens Skechers Microburst Imagination Shoe Style 23326 Black/White 196F pr , Womens Skechers Pink Running shoes size 6 , Nike Zoom Pegasus 32 Size 5.5 Y Girls Running Shoes 759972-001 Burgundy 2016 , CONVERSE All Star Black White Shoe Womens 8 M Slip On Sneaker Ballet Flat Canvas , New! Women's Puma 35421705-05 Athletic Shoes - SIZE 7 Black/Pink E24 , Women's Baretraps Mariah Women's FLATS Black Easy To Use Flats , Marc by Marc Jacobs Beige Bond Army Low Top Chunk Heel Sneakers Size 10Women's Nike FlyKnit Roshe Running Sneakers NEW Green/Black, MSRP $100Womens Nike Free RN Motion FK 2017 Size 8 (880846 004) No BoxNike Air Max Motion Lightweight LW Sneaker, Women's Size 9, Blue , New Converse Chuck Taylor Hi Looney Tunes Marvin The Martian Women’s Shoes Sz 9Womens Skechers Synergy Look Book Memory Foam BBK #BR 11963 , Womens Nike Free RN CMTR running shoes size 9.5 gray new in box low fast shipng
"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."