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.Talbots Womens Beige White Suede Casual Loafer Boat Deck Shoes Size 8 , Natural Soul Naturalizer Womens Sz 8 Loafers Vegan Buckles Hartman Shoes Moc ToeChaussure mocassin espadrille dorée nice shoes sexyNEW NWT Crocs Women's Mercy Work Black/Gold Shoe Clog Sz:7 , Soft Style by Hush Puppies Women's Valda Oxford, Pewter Snake, 7 N US , Nine West Women's Spruce D'Orsay Flat - Size 5 M, MauveVince Maxwell 2 Metallic Womens Shoes Size 6.5 M Flats MSRP $225 , Women's Alegria Black Patent Leather Gold Silver Rainforest Frogs Clogs Euro 37 , Clarks Privo Size 11 Wide Black Aria MaryJane Strappy Sporty Ballet Flats , Tory Burch Casey Driver Moccasin Flat Sz 7 Loafer Logo Blue/tan/mustardvintage DR MARTENS 9764 6 eye oxford brown grunge oxford shoes US 7 , New Breathable Women's Shape Ups Toning Fitness Walking Shoes Sneakers x6030H , Easy Street Women's Kila Flat, Brown Shimmer, 6.5 W US , Skechers Sport Womens Burst 2.0 Game Changing Fashion Sneaker- Pick SZ/Color.NIB CREATIVE RECREATION women W COTRONI Fashion BLACK HOT PINK sneaker shoe US 9 , Montrail Fluidfeel II Running Shoes - Women's Size 8.5 - FuchsiaReebok RunTone $90 Women's Running Shoes Size 6.5 Black Purple EUC , Women's H SHOES WOMEN'S SIZE 9 Excellent Craftsmanship Athletic Shoes , Women's Victoria K Brown Flats For Your Selection Flats , Mizuno Women's Wave Rally 5 Athletic Volleyball Shoes White/Black Size 9.5M , NIKE Women's Revolution 3 Black & silver 819303 015 Size 10.5Altra Womens Lone Peak 3.0 Neoshell Zero Drop Trail Running Shoes Size 10.5Saucony Men's Kineta Relay Running Shoe - Choose SZ/ColorNew Balance 990 Womens Running Shoe White/Blue/Gray Size US 5D (W990WB3)USA# , Saucony Women's Zealot ISO 3 Running Grey/Blue Shoes Size 6.5 US (N1,15)Adidas Shoes Galaxy Trail Purple Black White Womens 8.5 Sneakers Running CM7382 , NEW WMNS NIKE FREE VIRTOUS PRT QS 799829 100 SIZE 6~11 , Asics Gel-Cumulus 12 Womens Cushioned Running Sport ShoesSam Edelman Women's Gigi Thong Sandal Saddle Painted Tribal Leather , New Nike Womens Nike Free 5.0 PersianViolet/Aluminum/FuchsiaGlow/Black Running
"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."