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.ETC-LOVE BLACK SHOES WOMENS SIZE XL (10)LAUREN Ralph Lauren Brown Leather Snake Skin Penny Loafers Womens Sz 7.5 VGUC , Traditional women Black Punjabi Jutti Flip Flop Indian Khussa Mojari Flat Shoes , Trotters Silver Leather Slip On Flats Women's Size 7M.Soft Style Women's Heartbreaker Fuchsia SoundWave Flat 9.5MCLARKS WOMEN'S BLACK LEATHER MULES/FLATS SZ 7.5M IN VERY GOOD CONDITONWomen's Black SKECHERS "GOWALK 4 GoGa MAX" Loafers Size 7.5 M GREAT Condition , Women's Casual tom's rubber sole Slip on Shoes Authentic sz 9 FAST SHIPPING�Clarks Bendable Bootie Navy Size 8W Wide Leather Suede , Women's Brown leather Merrill Ortholite size 10 Mary JaneClarks Privo Flats Shoes - Strappy Casual Black Poppy Bloom Ballet Women's 7.5 MDrew Shoe Women's Lori II Mary Jane Hook & Loop Close Bone Leather Sz. 6 N , Softinos by FLY London Ako Red Nubuck Gored Demi Wedge Loafer, Women's , Nice DANSKO Barn Red and Brown Leather Loafers Eur 37 US 6.5-7 , Dr. Martens Size 6.5 Blue Oxford Women's - EnglandWomen's Outdoor Sneakers Shoes Casual Breathable Athletic Running Sports Shoes A , Luxury Womens Real Patent Leather Metal Peral Flat Heel Shoes Oxfprds Working SzCalvin Klein Womens Fridelle Closed Toe Slide Flats Black Size 9.5 vRWl , Alergria Paloma PAL-011 Patent Black Leather Mary Janes Comfort 39 Women's US 9LADIES SHOES/FOOTWEAR -Slip on lightweight Cherry Melody navyHOT NEW STYLISH LIFESTYLE WOMEN wt-056 PINK WINTER SLIPPER MADE OF COTTON , New Balance Womens Wt910gp3 Gray Running Shoes Size 9.5 (271223)Brooks Glycerin 14 Womens Running Athletic Shoes Size 7.5 D Wide Gray PinkNike Women's Racquette Training/Running shoes 443796-403 NEW IN BOX Size 7 , Womens Skechers Go Flex Running Walking Yoga Workout Gym Fitness Trainers , LL Bean Women's Gore-Tex Shoes Size 11 Medium Brown Trail Hiking , NWOB Steve Madden Burgundy Slip On Sneaker Size 10 FREE SHIPPING , Puma Women's Shoes Crete Sheen Silver Sneaker 347984-02 Women Size 7.5 Last PairSAUCONY KINVARA 6 Women's Running Shoes Size US 8 M Blue S10282-2 , NEW FILA SKELETOES BAY RUNNER WATER SHOES SIZE 5 WOMENS PINK GRAY NIB BAYRUNNER ,
"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."