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.7 Clarks Collection Women's Hayla Titan Brown Leather Clogs Mules Shoes BuckleBLOW OUT SALE @ BJORNDAL Leather Kara II Sandals Loafers Womens Shoes Sz 6 ❤️b3 , PIÚ DI SERVAS Cordovan Leather Heeled Loafers Size 6.5 UK/8.5-9 US Germany MINT! , SANUK ELLE WOVEN BLANKET PONCHO FLATS 9 , Women's Pastry Fashion High Top Sneakers Size 6.5 (B,M) Casual Multi ColorLucky Brand Emmie Ballet Flats Size 6.5 Nude Shimmer Metallic LeatherWomen’s Clarks Brown Leather Side Zipper Loafer, Size 8 ½ M**LifeStride Addy Flats - Women's Size 5 M - Silver , J-41 Strappy Mesh Women's Shoes size 7M GrayI Love Comfort Women's Shoes Mary Jane Maxie Casual Size 9.5 M Brown LeatherEcco Choice Comfort Slip On Shoes Size 41 (EU) 10/10.5 (US) Black , Zara Black Patent Flats Slingbacks Size 7 NWT , Dansko Savanna Mary Jane Clogs Shoes Sz 38 US Brown Leather Womens 2D1NWOB Woman's SAS Tripad Comfort Brown Suede Slip On Loafers Size 5M , Adidas Women's Cloudfoam Advantage - White - Sz: 9Converse ~ Skidgrip CVO Oxford Women's Sneaker Shoes $50 NIB , JOYA WOMAN'S 10 VENZIA WALKING SHOE BLACK SUEDE OTHOLITE SHOES SNEAKERS WEARABLE , Womens Suede Bowknot Embroidered Oxford Pull On Loafer Fur Lined Flat Heel Shoes , Ryka Streak SMR Running Training Athletic Shoes Sneakers Silver Blue Womens , REEBOK WHITE LEATHER SNEAKERS SHOES WOMENS 9 FREE SHIPWomen's Reverse UO Distressed Boyfriend's Jeans Fine Quality Flatswomen's shoes D.A.T.E. ( date ) 8 () sneakers blue silver textile BX59-39Saucony S60033-85: Originals Women's Shadow 5000 Classic Retro Running B Sneaker , adidas Originals Vengeful w Running Shoe - Choose SZ/ColorSkechers Sport 23048 Womens Breathe Easy Fashion Sneaker- Choose SZ/Color. , NIKE AIR FORCE 1 AF1 Navy Blue Leather Gold Polka Dot Fall 2018 Trainers - Sz 7NIB VANS SK8-HI SLIM ZIP (Leather) Whispering Pink Blanc Shoes SZ Womens 5.5 , New Balance Fresh Foam Zante V3 Running Shoes, Women's Size 10 B, White/NavyMerrell Siren Ventilator Mid Olive Women's US 9.5 Ankle BootsAdidas Arianna Cloudfoam Women's Running Shoes Sz.10 US Light Green NWOB ,
"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."