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.Fashion Womens Flats Hollow Breathable leather Loafers Preppy Bowknot Sandals SzDR ANDREW WEIL Ladies TWO TONED WOOL SLIDE MULES~SZ 6 M~GREAT CONDITION , IKRUSH Womens Lelli Glitter Zip TrainerMootsie Tootsie Loafers 7 Women’s Brown Suede Career Work Shoes Flats , Cole Haan Country Women’s RED Leather Mules Loafers Slides size 10 , NEW Women's Size 7.5 Candie's Casabaro Black Loafer Flats Slip On Shoes $54.99 , Piano Keyboard Music Note Lightweight Slip-on Canvas Women's Casual Flats ShoesBOC Born Nurses Shoes Clogs Leather Paisely Blue Navy Slip On Size 10 Woman’s , NAOT Size 7/Brown Leather Floral Embroidery Clogs Mules Shoes For Women , GREAT 10 N*est SAS TRAVELER BLACK LEATHER WOMENS COMFORT SHOES SNEAKERSSperry Top‑Sider Intrepid 2‑Eye Boat Shoe Womens Size 7M- Tan-Pre OwnedWomens HUSH PUPPIES Penny Loafers Size 7M Burgandy Wine Suede Leather Slip on , BOBS SKECHERS Women's Gold Memory Slip On Flats Shoes Size 7.5 , Jack Rogers Delaney Black Herringbone Silde on Shoes. Size 9 MCrocs Womens Freesail Clog Navy 9 M USKlogs Harper Womens Clog Shoes Display Model Leather Tex Mex 8M , JAMBU LIDO RED SUEDE LEATHER WOMENS 6M V-NICE V-CLEAN MARYJANE see pics-details , NEW MINNETONKA WOMENS KILTY DRIVING MOC SMOOTH , Steve Madden Prisila Tan Suede Espadrilles Size 9.5 New With BoxCircus by Sam Edelman Murray Womens Fashion Sneakers Strap Buckle Red Blue Sz 10Puma Women's Running Shoe Size 6 Silver Pink , Adidas NEW 11 Gore Tex Duramo Cross X GTX Bungee Sz Women's 11 M21159 , Nike Blazer Hi Top Sneaker Women size 11 PinkPropet Washable Walker Women's US Size 10 2E(x) White Walking ShoeEasy Spirit Traveltime Navy White Womens Clogs Size 7.5M , Puma Women's Platform Slide Bold Sandals Puma Black 367063-01Vans Authentic (Gumsole) Eclipse Light Gum Skate Shoes WOMEN'S Size 7.5 , Women's Nike Air Full Length Citius Running Sneakers Shoes Size 9.5 (W-104)Nike Air Max Kantara Athletic Shoes - Women's Size 7.5, Black , WOMENS NIKE FREE 7.0 SHOES SZ 9 M
"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."