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.Easy Street Women Flip Flops White Jewel Accent Cushion Sole SZ 7 W W1de NewREPORT IRRADISSANT GREY FABRIC BALLET FLATS SIZE 10Munro American M189411 Dark Brown Leather Slip On Apron Toe Loafers Womens 9.5MWomen's Lacoste Sport Mary Jane Pink Slip On Flat 9.5 Ballet Leather Ballerina , $69 size 5.5 Lucky Brand Elisabeta Nigori Crochet/Canvas Ballet Flats Shoes , Union Bay Solo Women’s Silver Slip On Fashion Mules US 8.5 M Shoes C222 , J-41 Jeep Womens Size 8 Vegan Loafers Slip On Shoes Walking Hiking Zipper Black , Looks New Womens Sofft Shoes Sz 8.5 M Brown Solid Clog ShoesCole Haan Tassle Penny Loafers 6 BLadies Shoes by FlyFlot - slipper - leather removable footbed - GraySAS Womens 9 WW Extra Wide Tripad Comfort Free Time Shoes Leather Oxfords 1U3 , Women Casual Outdoor Sneakers Fashion Comfortable High top Shoes Black 4554_EgWomen's LIORA MANNE Multicolored Paisley Design Clogs Size 37 , Ecco Womens Black Solid Leather Loafers w/ Touch Fasteners US Sz 8/8.5 EU Sz 39NEW! J slides Aztec sneaker leopard print size 9 , Women’s Nike Free TR 6 Black Size 6.5 , KURU womens gray blue Quantum plantar fasciitis walking trainers sz 8 , LAGUNA FOOTWEAR Stretch On/Off Waterproof/Surf Shoes Women's Sz 9 NEWBROOKS, Women's Cascadia 6, Size 8.5WOMEN PUMA FIERCE ROPE VR WN''S 190136-01 OLIVE NIGHT/WHISPER , NWT Converse All Stars Silver Glitter Low Top Unisex 12 Women 10 Men Fast Ship! , Guess Women's Gold Logo Print High Top Sneakers Shoes - Sz 8.5 , $130 size 10 KENDALL and KYLIE Reese Black Leather Sneakers Womens Shoes NEW , Dr. Scholl's Women's Frankie Mesh Flat Black Mesh Comfort ShoesWomen Converse Chuck Taylor AS Digital Floral Ox, 553298F Mul Sizes White/Neon PNEW MADDEN GIRL ADORREE NAVY SNEAKER SHOES WOMENS 6.5 FREE SHIP! , LACOSTE Barbuda Dl Lew Women's Shoes *Size 5.5(USA) 36(EUR) 3.5(UK) , Womens Brogue New Patent Leather Wedge Heels Creepers Punk Shoes Pumps Plus SizeNIB New Balance WT590LB3 All Terrain Trail Running Shoes - 8.5B , Brooks PureFlow P3 Running Shoes Womens Sz 4.5 D Lightweight Pink Purple C8
"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."