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.Women 9M Bass Mary Janes Espresso Brown LeatherMojari Women Shoes Indian Flip-Flops Handmade Jutti Leather Ballerinas US 5Call it Springs Ballet Flats Baige Size 6 usedEcco Women Heels Sz 10 Shoes Causal Professional Split ToeSesto Meucci Women's Multi- Color (Made in Italy) leather slides shoes sz 8 NBandolino Women's Best2ComeL1 Ballet Flats Black w/Cutout Details Size 6 MJ Crew Hot Pink Patent Leather Women's Sandal Flat Size 9.5 NWB , antia Shoes Women Size 8.5M Ballet Flats Flower Brown Leather Flats x111 , Sperry Lounge Away Women Sz 9 Washed Rose Slip On Casual Boat Shoes TX-30 , A35 Aleaa Ballet Flats 821, Nude, 6.5 USFitFlop Super T Athletic Fashion Sneakers Shoes Toning Trainers Canvas Size 9DONALD J PLINER DEVIN Womens 8.5M Brown Suede Leather Ballet Flats ITALYBritish Pointy Toe Low Cuban Heel Slip On Chic Women's Pumps Shoes Oxfords sz , Bass Jenny Espadrilles Palm Tree White Blue Print Size 11 M NIB , LANDS' END Size: 9 LINEN and LEATHER Flat Sandals NEW Туфли Женские , AO2722-001 NIKE WMNS Praktisk Women's Sandals Slippers Comfortable -ac , Good Cond Pony MX77 Low Sneakers White Leather With Blue Suede Sz 7.5 , New Balance 608 Womens Shoes Size 7.5M White Pink Running Sneakers -3514Women's Black Chuck Taylor Ballet Flats, Size 6 , Converse Chuck Taylor All Star Hi Shoes Classic Canvas Blue Women Size 7 M9622 , 02-1845 New Merrell J12398 Siren Hex Q2 E-Mesh Vapor Women's SZ 8.503-28 BROOKS ANTHEM 120257 1B 051 GREY/PINK SIZE 8.5B , Women's CLARKS Women's Teadale Rhea Oxford Beautiful Flats , MERRELL Moc WATERFROOF GREY Leather Shoes Sz 11 , adidas Originals Womens Superstar Glossy Toe W Fashion SneakerNEW Nike ZOOM FIT TRAINING sz 10 WHITE CRIMSON PURPLE Running Shoes SneakersNIKE WOMENS LODEN SZ 5.5 LIGHT BONE COOL GREY GUM BROWN OFF WHITE 896298 008 , Mizuno Wave Rider 20 - Women's Size 8 Teal/PinkSketchers Shape Ups SRR Resistance Women's Walking Toning Sneakers Size 8MVans Unisex Sk8-Hi Slim Cutout Sneakers Perf Suede Tarmac True White Size 7.5 Ne ,
"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."