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.BCBG EMILY Snake Reptile Print Ballet Flats Shoes Size 7Clarks Women's Slip on comfort shoes 8M Burgundy Upper leather velour embroider , Dexter Women's Brown Leather Slip On Moccasin Boat Loafers Size 7.5 M , METRO 7 Glitter Black Bow Flat SHOES Open toe Rubber sole size 7 , Nadya-08 New Fashion Buckles Zipper Flats Cute Comfort Sandals Party Women Shoes , J Crew Sz 7.5 Cece Ballet Flats Tortoise Patent Leather Slip On Gray Black , Womens Dr. Scholls Beige Leopard Buckle Slip On Ballet Flats Shoes Size 10 M GUCBorn Tan Suede Women's Loafers Moccasins Buckle Sz US 9.5 W7528 , SPERRY Top-Sider Women Boat Shoes Size 10 M Multi-ColorWomen's Dansko Size 41/10.5-11 Loafers Clogs Shoes Black Leather Nursing V7Chic By Lady Couture Blossom Peep Toe Jelly Dressy Flats Choose SZ/ColorStuart Weitzman Snake Embossed Black Leather Beaded Tassel Loafer Sz 8.5 AASloggers Multi-Color Floral SHOES WOMENS SIZE 10 , Crocs Women's Size 5 W Faux Fur Lined Clog Slip-On Slide Mule Moc Shoes , Sanuk SWF10080 Womens Fiona Slip-on Loafer- Choose SZ/Color. , Nike Running Shoes Gray Synthetic Women7.5Medium (B, M)Chic Street Womens Slip on Loafers Fur Furry Rhinestones Satin Shoes Pointy ToeAerosoles Women's Betunia Loafer Black Houndstooth Size 6.0 , Franco Sarto Womens CENTARA Leather Cap Toe Ballet Flats, Black, Size 6.5 , adidas ZX Flux - Grey - WomensNew Balance Womens Brown Tennis Shoes Size 8 MWomens Converse All Star Chuck Taylor Size 7 Shoreline White Shoes SneakersK-Swiss Women's Clean Court Fashion Sneaker,White/Silver, 9 M US , SKECHERS Womens D'LITES Life Saver Black Casual Athletic Shoes Sz 6.5 F5-334 , K-Swiss Women's Classic VN Iconic Fashion Sneaker - Choose SZ/ColorNEW Womens NIKE RUN SWIFT Athletic RUNNING SHOES gray purple Size 9adidas Women's Ultimafusion Running Shoeballerines REPETTO, pointure 35, cuir de couleur noire , 23259 Black Skechers shoes Memory Foam Women Comfort Casual Slipon Sneaker WovenTop Moda Womens Sammy-40 High Top Strap Womens Hidden Wedge Sneaker Shoes
"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."