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.Luck Brand Eleesia Black Patent Leather Ballerina Elastic Flats Shoes Size 5.5 , Sam Edelman Women's Blue Snakeskin Printed Cuban Pointed Toe Ballet Flats Sz 8 , Ladies Black Casual Shoes with Riptape StrapROCKPORT Slip On Comfortable Shoes Women's Size 9 , US Punjabi Jutti Flip Flops Casual Shoes Khussa Shoes Mojari Women Jooti DD890EDDIE BAUER Slip On Loafer Style Shoes Tan Suede Women's Size 10 Rubber Soles , TALBOTS Women Ballet Flats Size 8B BlackSperry Top-Sider Embossed Snakeskin Grey/Metallic Silver Leather Boat Shoes- 6MBorn Brown Leather Mary Jane Flats US 9 M/W , Brian Atwood Blue Pony Hair Ballet Flat 7Cole Haan 9 Extra Narrow Green Slip-On Shoe Women'sMini Melissa Kids' Ultragirl Sweet III Black Size 3 Medium US Little Kid Y70y , Alegria BEL539 Black Holographic Floral MaryJane Shoes Womens Nurse 40 US 9.5-10 , Reebok Women's Transfusion 3.0MTBlack/Ornage/Magenta Training Sneaker 11M , Windriver Women's Brown Mid-Cut WP Hiking Shoe 10M , Genuine Leather Silver Trim Stitched Diamante Bling Espadrilles Slides Shoes , KEEN Elsa Slip On Women’s White Canvas Rubber Soles Toes Shoes US 11 C398Fila Womens Running Shoes Size 11M Purple Gray DLS Foam Sneakers -2567 , K Swiss Belmont Womens Girls Classic Leather Casual Retro Trainers White , AR35 Shannen Slip On Sneakers, Platino, 6 USWomen's Reebok Cloudride DMX Training Running Shoes Size 6 US , Vans Milton Hi Top Zip White Leather Sneakers Shoes VNOA32Q3kVK Size 9.5 NEW , New Rebecca Minkoff Size 6M Stacey Stud Black Lamba Platform Leather Sneakers 6MHoka One One Women's Challenger ATR 3 Athletic Training Running Shoes Size 8.5 , Derby Baskets SAIMON Cuir Marron et Beige T 40 Etat NeufNew Balance 940v3 Stability Womens Running Training Shoes Size 10 Blue Gray , WOMEN'S NIKE AF1 ULTRA FORCE ESS SHOES SIZE 11.5 white grey 749530 100Skechers Women's Relaxed Fit Bikers Fashion Frontier Mary Janes Shoes-Size 6/8Rare JC Play Jeffrey Campbell Platform Sneakers Monkey Print Size 7 , Shoes Skechers Empire Sweet Scene 12413 tpe Womens Taupe Casual Sneakers Slip on ,
"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."