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.Taos Women's Cobbler Oxford - Black Leather - Size 11B , Apex Women's Lisa Brown Classic Mary Jane Flat 8.5Minnetonka Tan Suede Soft Pile Lined Moccasins Size 6 Nice!Ladies Keds Canvas Shoes Label DBL Dutch Stripe , BASIC EDITION Faux Leather Sandals Flats in Black ~ size 8W/8.5 ~ NWOBFranco Sarto Devra Women's Tan Floral Suede Slip On Mule Sz 7.5W 2091NIB BOC Franki Womens Espadrille Flats Shoes 9.5 Dark Brown MSRP$70SOFFT women's slip on loafer flat BROWN leather jute 11M NICE EUC , J-41 by Jambu Womens Black Vegan Mary Jane Strap Flat Comfort Outdoor Shoes 7M , Women's Bass Weejuns Katherine II Medium Leather Loafers 9 M , BORN Women's Leather Black Mary Jane Flats Loafers Shoes 8 M/W 39 , Cole Haan Air Niki Mary Jane Women size 9 AA Leopard , Jessica Simpson Mandayss Ballet Flats With Crisscross Straps Choose Sz/Color , Munro American Women's Black Suede Leather Ramie Loafer Size 7.5NNew Balance Womens 575V2 Blue Running Shoes Size 7.5 (C,D,W) (262833)Womens Puma Lift Running Shoes Trainers Sneakers US 9 , Clarks Wave Wimen’s Black Suede 86508 Comfort Shoes Suze 8MTrotters Women's Americana Flat, Black Croc, 6 N US , Asics Womens Gel Frantic 7 Running Shoes Sz 10 Teal Yellow PurplePUMA Suede Classic Sneaker Gray Pink Size 6.5 NIB $65 , Women's Nike Revolution 2 Running Shoes, 554900 034 Sizes 5-8.5 Cool Grey/Fuchsi , WMNS NIKE FREE 5.0 FLASH SZ: WMNS 7 (685169 001) RETAIL: $115.00 , STEVEN by Steve Madden Hilda Slip On Fashion Sneakers, BlackMerrell Womens Size 8 () Siren Edge Grey J35516XLNT WOMENS ASICS GEL-Kayano 21 Womens Purple Grey Silver 8, 39.5 EUR , New Balance Womens 7 WTNTRLB2 Running Sneakers Shoes Sneakers Black BlueBronx Women's Zoo Nee Fashion Sneaker,Natural,39 EU/9 M US , FootJoy Classics Sz 6.5 A Women White Brown Saddle Golf Shoes NWOT YGI C7-50Mizuno Wave Hurricane 3 Womens Volleyball Shoes Size 9 USED Black , Skechers Sport Women's EZ Flex Flicker Slip-On Sneaker 22832 Sz 5 Charcoal Gray ,
"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."