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.Studio 36 Women's M200 Peep-Toe Flats Burgundy Leather Size 7.5 MAldo Onalen 32 Women's Ankle Strap Flat SZ 8.5A2 WOMENS BROWN SANDBAR COMFORT LOAFERS SIZE 10M , BORN Womens size 6.5 Black Leather Mules Slip on Shoes Clogs , Dansko Burgundy Red Leather Loafer Clog Casual Work Shoe Slip On US 6 , Torrid Women's Silver Metallic Flamingo Pointy D'Orsay Flats 10W WideCole Haan W03205 Womens Zerogrand Marine Blue Sz 8.5 B$135 CHARLES PHILIP SHANGHAI NB-03 Lime Canvas Designer Flat 8.5 RUN SMALL , Taryn Rose Kelsey Brown Stretch Ballet Flat Wedge Women's 40 / 9-9.5ZARA NEW WOMAN STUDDED LOAFERS FLAT SHOES CUT-OUT SIDES BLACK 35-42 REF.7540/301 , Newton Lady Isaac Neutral Guidance Womens Running Training Shoes Size 10.5 , ?Women’s Converse Chuck Taylor Gemma Craft Slip On Shoes Size 9 New!!? , Buffalino Boots Women SZ 10 Slip On Mules Clogs Navy Denim FREE SHIPPINGNWT Zara Women's Black & White Slip On Shoes/ Sneakers, 37 EU size 6.5 US sizeWomen's Brooks Glycerin 12 Running Shoes size 7.5 , Saucony Blue/Pink/Black Contana 4 Running Shoes Sz 5.5 W/Original Box , ASICS Women's GEL-Venture 3 Athletic Running Trail Shoes T283N Size 8 , Vintage 90s New Asics Womens Size 5.5 Gel Saga Sneakers Shoes White Lilac Black , Saucony Excursion TR10 All Terrain Shoes Womens Size 6.5Puma Basket Classic Citi Metallic - Metallic - WomensWomens Brooks Ravenna 7 Athletic Support Mesh Light Running Shoes Size 10.5Altra Zero Drop Paradigm 1.5 Running Shoe Women's size 7 EUCadidas edge lux w - Grey - Womens , Skechers BOBS Women's Squad-Star Chase Sneaker - Choose SZ/ColorASICS Womens Gel-Equation8-W White Running Shoes Size 7.5 (356177)Rider Women's Dunas XI Thong Sandal Blue/Brown Thong Sandals , Pony, Womens 10, 27 cenitmeters ( may fit 8-7.5 mens, please measure) , Women's Fashion Sneakers Slip On Casual Loafers Round Toe Platform Jogging Shoes , Nike Benassi JDI Slide Women's White/Wolf Grey/Metallic Silver 43881107rare SOLOMON SPEEDCROSS 3 Trail Running shoe EU44.5 men's 9.5 / women's 10.5 ,
"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."