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.Clarks Leather Slip on Shoes Evianna Fig PEWTER 6 MEDIUM , NEW Womens MIA GIRL PLAY BLACK Loafer Slip On Flats Loafers Casual Shoes SZ 8Classical Womens girls flats Canvas Ankle Shoes bandage splice Spring boots new , Ralph Lauren Women's Yolanda Boat Shoe, Dark Brown, 8.5 B US , Womens Born BOC "Peggy" Animal Print Leopard Brown Patent Leather Clogs Size 6mDr Scholls Sz 8M Slip On Loafers/ Moccasins Double Air Pillo Insoles E 61-RH SD , Ballerines Babies MINELLI Cuir Daim Taupe Mauve T 40 --> 41 TBEVINTAGE HUSH PUPPIES Olive Green Suede Leather Slip On Loafers - Women's 8Clarks Everlay Bai Mary Jane Loafer-Women's size 8.5M BrownPaul Green Womens VEDA Closed Toe Espadrille Flats Sabbla Size 10.5 5a8rEcco Mobile III Premium Sneaker Moon Rock Grey Women's Sneaker 40 / 9 - 9.5 MNike Women's Tailwinds 6 Athletic Running Shoes Size 9Easy Spirit Takeit clogs mules jersey knit soft fabric light grey 6.5 WIDE NewJ Crew Italy Womens Size 8 Red Suede Leather Driving Moccasin Slip On ShoesWomens Ladies Flat Stretch Knee High Riding Boots Grip Sole Winter Shoes Size , Hoka One One Bondi 4 Womens Purple Coral Running Shoe 10.5 M , Saucony Progrid Kinvara 3 Running Shoes Womens Size 7.5 White/Pink/Neon , Vionic Alliance Black Casual Orthotic Diabetic Walking Shoes Women's Sz 9Skechers Reggae Fest Dory Women's Sz 8.5 Gray Open Sided Sneakers Shoes ZV-1005Asics Gel Excite 4 Running Training Shoes Womens Size 9 Gray Purple Pink A9 , Women's NIKE Zenji F Bleu Moderate Price Athletic Shoes , NEW COLE HAAN WOMENS WOMEN'S GRANDPR? TENNIS SNEAKER - OPTIC WHITE-ARGENTO S...Converse Chuck Taylor All Star CT HI Rise XHI Women Shoes Black/White 549587f , Skechers Performance Women's Go Step Lite-14739 Walking ShoeNavy9.5 M USNIKE WOMEN'S METCON REPPER DSX SHOES SIZE 11 black pink blue 902173 002Nike LUNAREPIC FLYKNIT OC 844861 999 Womens Running Multi-Color SZ5.5 NO BOX TOP , Adidas Round-It Mid W Black/White Leather Athletic Shoes Size 8 #G60859Hi-Tec Women's Skamania Wp Ankle-High Suede Hiking ShoeConverse for Women CT Ox Parakeet Black Sneaker low top multi colored sulpineADIDAS EQT RACING ADV PRIMEKNIT CQ2240 SNEAKERS WOMAN LIMITED EDITION SPRING 201
"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."