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.B.O.C Born Womens Leather Slip On Clog Loafer Mule Heel Shoe Size11Aldo Brown Ballet Flats Size 39 US 8CROCS 15317 STRECH YOUR SOLE CANVAS SPORT PINK ORANGE BOAT LOAFER SHOE Women’s 9 , MUNRO Shoes 10 M Leather brown Flats Penny Loafers Slip Ons made in USA comfort , Trotters KIM Women's Leather Penny Loafer Shoes Size 8.5N, Brazil ~FREE SHIPPINGDansko Clogs woman's shoes black leather , Teva Women's Willow Slip-On Ankle-High Canvas Flat ShoeFinn Comfort Narita Woman's Shoes German Made Sz 8 Black Cushioned Insole , WOMENS SHOES-P.W.MINOR MARY JANES ATHLETIC SHOES-ZOEY-TAN SIZE 9.5(2E)-EUCLolita Girl Women Pink Leather Cross Elastic Strap Ballet Flat Ballerina ShoesJ-41 Shoes Womens Size 11 Brown Slip On Shoes Jeep Engineered Traction SoleSaucony Womens Running Shoes Size 7 Teal Purple KINVARA 6 , NEW $69 Womens Skechers Performance Go Walk 3 shoes, size 11 stone/white , KEDS Women's Casual Flat Shoes, Fashion Sneakers BROWN SIZE US 8Mizuno Wave Inspire 12 Running Shoes Purple Synthetic Women 7 Medium (B, M)Adidas GLC Women's 6 High Top Shoe Retro Basketball Torsion Shoes , WOMENS NIKE ULTRA COMFORT FLIP FLOP | 882697 001 | BLACK - WHITEWomen's converse all star size 6. Color Black & White. , Ryka Desire Lightweight Running Fitness Athletic Shoes Sneakers Size 8 , PUMA Tazon Cross Training Shoe - Women's Size 7.5, White/PinkMen's Shoes Slippers Glerups Boot Slipper Grey 40.0 Diversified Latest Designs Slippers , Women's Vans Boat Shoes Big Clearance Sale Athletic ShoesADIDAS ORIGINALS SUPERSTAR FOUNDATION WHITE/Blue S74944 Women's Sneakers ShoesUSED Vibram WOMEN'S Bikila EVO Red/Yellow EU SIZE 37 AUTHENTIC 15W3102Demonia Women's Creeper 118 Creeper , Asics Gel-Lyte Komachi White/White Women's Running Shoes H750M-0101 , Vintage Deadstock Ecko Red Phranz Phusion White / Pink Size 5.5 Women Sneakers , NEW! Under Armour 1266243-914 Womens Micro G Speed Swift Aqua/White 8.5M 101P aa , Original Kitson Sketch 34530 NTBR Buttons Casual Women ShoesWomen's Converse Chuck Taylor All Star Double Tongue Sneakers Black/Pink 558580F ,
"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."