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.424 Fifth Womens Gabby 1 Blue Embellished Loafers Flats 6 Medium (B,M) BHFO 0367LADIES SAVANNAH LIGHT GOLD FLAT SEQUINED SHOES STYLE: F80070Ladies Eaze Leather Slip On Ballerina Shoes with Bow & 1.5" Wedge Heel F3091 , Adidas NEW Original Stan Smith Womens 8.5 40 2/3 Leather Sneaker Shoes BB1433 kk , Women's The Flexx Snakeskin Stretch Run Slip On Shoes Gray Silver Black 37/6Dansko Emily Shoes Women's Mules Clogs Beige/Tan Suede Leather Sz 5.5-6.0 / 36Aerosoles Women's Spin Class Ballet Flat, Black Combo, Size 7.5 , Charles by Charles David Women's Georgi Loafer, Gold/Metallic, 7 Medium US , Enzo Angiolini NEW 8 M Lizzia Tassel Loafer Flats Black Rich VelvetTory Burch 'Santa Fe' Espadrille Cactus/Pepper Rare 10M , Asics Gel-Evate 2 Fluidride Black Pink Athletic Running Shoe Women's Size 9 T4A7*FAST TURN* VINTAGE HIGH TOP COURT SHOES "SLAM-DUNK" KHAKI SZ 10Aldo Womens AMAILLA Closed Toe Loafers, Silver, Size 8.0 e2VpVibram FiveFingers Womens Size 41 Bikila W346 Blue Barefoot Running Shoes , Nike Air Pegasus 29 running shoes sneakers women's size 10New Balance Womens 910V3 Trail Pink Trail Running Shoes 6 Wide (C,D,W) BHFO 1145Converse All Star Madison Sneakers Women's Size 5 Gray White Excellent Not Worn , Women's Converse All-Stars Leather Superior Athletic Shoes , Women's adidas flb womem casual shoes New Products Athletic Shoes , Women's Blush Puma Sneakers Size 7.5 Diversified In Packaging Athletic ShoesNike Flex Experience RN 5 Womens Running Trainers 844729 Sneakers Shoes 004Nike Women’s Air Zoom 90 IT Infrared Size 8.5 Spikeless Golf Shoe 844648-100Brooks Dyad 9 Navy/Pink Running Shoes Women's US 7.5 2E (N1,5)Nike Wmns Lunar Lux TR 749183 100 , Vans X Liberty Art Fabrics Women's Era 59 Red Floral Women's Sizes BRAND NEW! , nike womens blazer mid lthr trainers 525366 501 sneakers shoes CLEARANCE , Mizuno Wave Paradox 3 | Sz. 7.5 Women's | New (see details) | Running , PUMA Women's Suede Heart Satin II Cameo Brown Size 8.5SAUCONY EXCURSION TR10 SNEAKERS WALKING RUNNING TRAIL WORK SHOES WOMENS SZ 7 , CONVERSE CHUCK TAYLOR ALL STAR DAINTY US 6.5 SNEAKERS MINT GREEN ,
"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."