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.SEYCHELLES "BEST FOR LESS" Black SUEDE LOAFER/SHOES WOMEN SIZE 8 med NEWAnn Taylor Loft Aubrey Snakeskin Pointy Toe Flat - Size 10 - Worn Once , Womens Shoes Hunters Bay size 6.5Clarks Women 6M Brown Leather Bootie Heel Slip On Loafer Ankle Boot 88803 , Sperry Top-Sider Women's Bahama Boat Shoes Size 7.5M Gray Wool 2-Eye 9445404Womens Girls Casual Comfy Bowknot Ballet Flat Shoes Korea Slip On Loafer OxfordsCervelle Tan Brown Beige Snake Skin Pointed Toe Shoes Womens 8 Flats VintageKenneth Cole REACTION Women's Pro-Time Elastic Ankle Strap Back Navy Size 9.0 , Oxfords Womens Girl's Casual Block Mid Heels Round Toe Shoes Ankle Strap Sandals , Sperry Top-Sider Womens A/O Black Studs Boat Shoe 7M , $140 IVANKA TRUMP KENNI 6 Red Black Designer COMFORT Smoking Flat Loafers 6 , Chloe Womens Ballet Flats Size 38.5 White Leather Perforated Scalloped Slip On , ASICS Women's DynaFlyte Running Training Diva Pink/Silver/Black Size 9.5Saucony Hurricane 16 Running Shoes Womens Size 7.5 Green Gray Athletic Sneakers , Nike Womens Black Running Shoes Size 8.5 (13710) , NIKE FREE 5.0 WOMENS SIZE 8.5 GREY, SALMON RUNNING SHOES , MERRELL SIZE 5 Chameleon II (2) Web Leather gray / lime Women's Trail/Hiking , Women's Skechers Ultra Flex First Choice - Black - Width: med - Fashion Sneakers , NEW! New Balance Women's Running Shoes Purple/Grey/Orange A dz , Women's BURST W GRIS BLANC Quality Product Athletic Shoes , Dolce Vita Perforated Black Leather Casual Slip On Sneakers Women’s Size 9.5 MPuma Size 9 White Running Sneakers New Womens ShoesNike Flex Fury White/Gray Low mens 705298 100 US Size 12.5 , The Fix Women's Jaylene Slip Fashion Sneaker, Black/White, 10 B USSkechers ONE Element Ultra - Pink - WomensPuma x Fenty by Rihanna The Trainer High White - Womens - Size 9.5 BReebok breast cancer memory foam running shoes , Adidas Women's Shoes Originals Honey Low Shoes 013113 Womens Sz. 5-10 AvailableNike Women Lunar Element Gym Shoes Black / Metallic/ Silver Size 11.5 , NEW BALANCE 608 Running Walking Leather Athletic Sneakers Women Shoes Sz 9.5 W ~ ,
"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."