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.Isaac Mizrahi Live! Menswear Suede Loafers with Bow AURORA PICK SIZE & COLOR NWSPERRY TOP-SIDER Women's Boat Shoes Bahama Fog Leopard SIZE 5.5M , SURF SIDERS by VANS Women's Green Suede Moccasin Casual Flats Shoe Sz 8 SlippesROCKPORT Leather Loafers Sz 8 Made In BrazilSkechers Relaxed Fit Reggae Fest Dory Slip-On Sneakers Women's Size 11Patagonia Women's Size 7 M Soft Leather Maha Sling Sable Brown NewAlfani New Isszee Black Womens Shoes Size 6 M Flats MSRP $69.99 , Hush Puppies Chaste Leather Ballet Flats - Women's Size 9 EW, BlackMunro America Black Loafer Women's 9N LeatherNew Balance Women's Shoe Size 5 Athletic Shoe Comfort Graynew thick white shoes ladies' casual shoes women's casual shoes women's shoes , ASICS Gel Venture 5 Sneakers Running Shoes T5N8N Titanium Pink Womens Size 11 , ELECTRIC STYLES SNEAKERS WHITE SHOES WOMEN'S SZ 6.0 M LIGHTS DOES NOT WORK--621 , Naturalizer Marianne Slip-On Fashion Sneakers / Mauve / SIZE 9.5 WW /New In BoxWomen's Forever Link Relax-1 Womens Shoes Elegant Appearance Athletic ShoesNike Free Combat TR trainer womens 5.0 535852-200 New authentic! , Reebok Women's Classic Racer Relay Sneaker,Blue/Royal/Sonic Green,7.5 M US , EUC ASICS Women GEL-Kayano 20 Black T3N7N Athletic Running Sneaker Shoe Sz US 8 , Rider Women's CW Smoothie Thong Sandal White Water Resistant , Saucony Womens Pink White Gray Running Shoes Sneakers USA Size 11 EURO 43Women Running Shoes Fall Sport Shoes Light Sneakers Athletic Shoes Walking sales , Sperry Top Sider New Womens Acklins Hi Top Sneakers 6 M Shoes NWOB , Nike Wmns Lunartempo 2 RF E II Jungle Pack Navy Women Running Shoes 849815-600Montrail WILDWOOD TR Gray Pink Trail Running Shoes Women's - NEW - GL2047Asics Spivey LD Women’s Running Spikes Shoes G352Y Pink Silver Size 11 , Pollini Midnight Glitter Sneakers Low Tops - Limited , Converse Women's Chuck Taylor Hi-Rise Extra High High-Top Canvas Fashion SneakerJuicy Couture Women's Chester High-Top Black/Silver Sneakers - Size 6 NWB , POE-POWER OF ESSENTIALS WOMENS FASHION SNEAKERS IN GOLD SIZE 9US/39EU/7UK- EUCPuma Vikky Platform Color lavender Size 8 New with box Free shipping ,
"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."