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.Skechers GOwalk Suede Faux Fur Shoes Captivating pick size colorNew In Box Cute Espadrilles With Floral Embroidery! Retail For $250! Size 36 , WOMENS LADIES FLAT CREEPER CHUNKY SOLE SCHOOL WORK DOLLY LOAFERS BOW SHOES SIZEG.H. Bass & Co. Ladies Size 6 rubber garden shoes, forest green Q886 Rain , $118 size 6 Avec Les Filles Myrina Pink Leather Loafers Ballet Flats ShoesMerrell New Strap Sandals Black 8 Buckle Select Fresh Air Cushion Platform MidMichaels Kors Women's Black Leather Pointy Toe Flats Pointed Shoes Loafers Sz 9 , Cole Haan New Pinch Weekender Silver Womens Shoes Size 6.5 M Flats MSRP $100Soludos Women's Espadrille Slip-On Smoking Slipper HD3 Safari Canvas Size US:6Alice And Olivia Stacey Bendet Drake Black Plaid Studded Smoking Flats Size 6 , Kelsi Dagger Brooklyn Women's Border Oxford , New Pg Lite Women Mary Jane Mediacare-coded Shoes 6603-D size 6.5D , ESPRIT Odette Scalloped Edge Ballet Flats, Dove Grey , RARES CONVERSE ALL STAR ECRUES BE T 37 A ACH IMM FP RED MOND RELAY TOPKeds 6.5 M WH14169WH6CH17 Leather Sneaker, Beige Leather , Women's Velvet Pointy Toe Mary Jane Buckle Strap Flats Slip On Shoes Plus SizeAsics Gel Kahana 6 T2E6N Duomax Womens 9.5 Running Training Shoes Pink V11 , FILA Womens Tennis Shoe Outreach Mint Green Gray Memory Foam Pick Size , Wmns Nike Lunarswift+ 3 woman's sz 10Adidas Vigor TR 2 Trail Running Gym Shoes Purple Sneakers G56300 Women Size 8.5Nike Free 5.0 TR FIT 5 Women US Size 8 Black & White Swirl Running Shoe , Women's inov-8 all train 215 Womens Crazy Price Athletic Shoes , adidas Performance Womens Alphabounce EM W Running Shoe SZ 11 Mystery Blue NIB , BZees Sea Dogs by Wink Slip ONS Water Shoes , Vans Authentic (Gumsole) Eclipse Light Gum Skate Shoes WOMEN'S Size 7.5Asics Gel-Fit Yui Athletic Shoes - Women's Size 7.5, Black/Silver/WhiteJORDAN SUPER FLY 5 MEN SIZE 12 BRAND NEW NBA MELOKOBEWomens ASICS GT-2000 3 T550N Running Training Athletic Shoes Gray Pink Size 6.5New Nike Womens zoom condition tr trainer shoes 852472-014 Sz 7.5Nike Free 5.0 gray chevron womens size 9 ,
"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."