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.NEW Women's SOLESENSEABILITY ELLEN BLACK Slip On Loafers Shoes SZ 9Lucky Brand Emmie Pineapple Slip On Ballet Flats Shoes Womens Size 6 M EUC , croft & barrow with Ortholite shoes , Lamo Ella Lilac Womens Canvas Slip On Memory Foam Vulcanized Sole Loafer Casual , Bandolino Slip Ons Flats Women Loafer Black Tan Buckle Shoes Size US 11MCROCS Women Black Flats Size 9 NEW , American Living Womens Donica Closed Toe Ballet Flats , Marc Fisher Flats Womens Size 7.5 Nude Leather Buckle Black Toe-2644Privo Clarks Mary Jane Womens White Leather Perforated Black Stripe Shoes Sz 6B , EARTH Women 5 M Rally Navy Sea Blue Leather Mary Jane Slip On Loafers Shoes NEW! , Aerosoles Women's Millionaire Flat, Black Leather, Size 6.5AGL Attilio Giusti Leombruni Women Ballet Flats Shoes Snakeskin Cap Toe 38Gentle Souls Women Portobello LE Penny Loafer Moccasin Shoe, Saddle, US 5.5 , Mer du Nord Collie Ballerinas with Buckle (Sz 37) , Womens Mixed Color Heels Sneakers Running Breathable Athletic Sports Shoes 6 7 8Skechers Bikers MJ Casual Shoes, Offwhite, Cracked Leather, Women's US 9 , J-41 Bouquet Womens Loafers Black Vegan comfort shoes Size 7.5 MNIKE FREE RUN PURPLE WOMEN'S SZ 9Women's Ryka Heather - Navy/Blue/Pink - Width: med - Cross TrainingAsics Amplica Women's Runing Shoes Mid Grey/Silver/Aruba Blue T875N-9693Women's Nike Gray and Pink SneakersAmerican Wirehair Cat Running Shoes For Men-Free ShippingVans SK8 HI SLIM Cutout Square Perf/Amberlight Women's Shoes 5 , adidas Originals Women's Crazyflight X 2 Volleyball Shoe - Choose SZ/Color , New Women's Puma Suede Platform Gold Size 8Jack Rogers Women's Kamri Thong Sandal Cognac Faux Leather Thong SandalsVans SK8-Hi Wool Stripes Shoes Women’s Size 10 NewWMNS Nike Dunk Sky Hi PRM [585560-700] Casual Leopard Gold/Dark Armory BlueSteve Madden Gills Sneaker, WOmen's Size 10 M, NaturalSkechers Women's Go Vulc 2 GLINT 14593/NVY Navy Brand New
"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."