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.ROPER Womens US 6M Black Faux Leather Pointy Toe Western Style Mule Clogs ShoesDELMAN BROWN PATENT LEATHER CLASSIC DRESS FLATS SHOES , Womens Ladies Fluffy Sliders Black Sole Slippers Slides Sandals Fur Shoes Size , Nice NWOB Banana Republic Gold Flats - Size 9 BWomen's Life Stride Soft System Navy Blue Slip On Shoes Loafers Oxfords Sz 6 /37Klogs Spokan Women's Clog Shoes Display Model Smokey Blue 5MEurostep Brown Leather Stretchy Microfiber Slip On Loafers - Women's Size 11 MChic Women Brogue Carved Collegiate Oxford Shoes Chunky Patent Leather Boots R69Bass Weejuns Womens Wayfarer Leather Penny Loafer Slip On Shoe Sun/Gray/Whte 6 M , New JUICY COUTURE RACINE $225 Black Leather Ballet Flats Studded Shoes Women 6M , Fabulaire Fabulare Fabric Black Women Shoes 8 M Flat Slingback Square Toe , Eddie Bauer Italy Made Womens Sz 7M Brown Leather Slip On Boat Shoes Loafers DA5 , Reebok FURYLITE Classic Junior NEW size 6.5 Big Kid = 8 women Medium Black / RedSaucony Womens Raptor TR 7 Running Trail Hiking Shoes sz 9 f873 , Women Shoes Sneaker Platform Athletic Climbing Sports Breathable Hot Sale Sbox14Soft Plush Fleece Warm Indoor Men Household Winter Slippers Shoes Skidproof , Reebok Easytone White Purple Womens Size 6Merrell Arabesque Bamboo Green Mesh Zipper Running Sneakers Women's US 7Aerin Norumbege Women Size 8 Red Sneakers , Women's GEL MOVIMENTUM NOIR OR Durable Service Athletic Shoes , Nike Wmns Flex Essential TR White Wolf Grey Women Training Trainers 924344-100Amazing Newfoundland Dog-Women's Running Shoes-Free Shipping-For 24 Hours Only , Skechers Sport Women's Burst City Scene Fashion Sneaker , Converse Chuck Taylor All Star Fire Brick/Black/Grey Hi Top 148529C Men 6 Wo's 8 , Alegria Women's 39 US 8.5 Leather Sandals Black & Gray Slide Wedge Shoes R7S6 , Life Stride Women's Dreams WedgeMizuno Womens Wave Inspire 10 Running Shoes, White/Black/Blue, US 7 WideReebok Women's Turquoise Black Running Cross Training Shoes Size 8 US , ASICS Hyper Rocketgirl 5 Track and Field Spikes Women's 10 - new Free Shipping , Merrell Jungle Moc Women's Sz 7.5 Blue Suede Athletic Slip On Sports 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."