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.**Report Mick Flats - Women's Size 8, Black , Bellini Womens Loafer Blue Agusta Chain Ornament Size 9 M , BARE TRAPS Landon Brown Leather Mary Janes Shoes Women's Size: 8 M , Clarks Artisan 16734 Strap Ruched Casual Driving Loafers Black Women's US 7.5 , Hush Puppies Women's Silver Sparkle Flats 5 MSAKS FIFTH AVENUE Red Patent Leather Horsebits Driving Moccasins 7Sesto Meucci Animal Print Leopard Comfort Yasemin Waterproof Loafer Pump Sz 8 , Naturalizer Womens Saban Leather Closed Toe Loafers , Clarks Slip-on Loafers - Ashland Bubble Women’s Size 10 Brown Multi , Womens Havaianas Top Rubber Casual Beach Shoes Thongs Brazil Flip Flops US 4-11 , Marc Jacobs Ballet Flats Dark Teal Size 6 Leather Round ToeBearpaw Casual Shoes Womens Calla Zipper Fuax Leather 1760W , VANELi Womens Shera Closed Toe Ballet Flats , Bare Traps Womens bizzy Fabric Low Top Slip On Fashion Sneakers , Nike Free 3.0 V3 Running Shoes Pink Synthetic Women9Medium (B, M)Paul Green Munchen Tasha Black Patent Square Toe Loafers Womens 7.5 US / 5 UK , Women's Keen Dry leather hiking shoes boots size 6 , Diadora DA8AMS5890 Black White Grey Men Slip On Water Sports Sandals Shoes , Skechers Go Step Lite Indulge Boat Women's Shoes , The North Face Ladies 7.5/38.5 Endurus TR Trail Running Hiking Athletic SneakersNew Balance Womens Wxnrgbh Black Cross Training Shoes Size 10 (C,D,W) (425057) , ADIDAS WOMENS ALPHABOUNCE CR CG4674 BLACK , Nomad Women's Puddles II Coral Moroccan Trellis Water Resistant8.5 US ladies tan houndstooth RAS sneakers shoes Eu 39Merrell Siren Hiking Shoes-Women's size 6.5 W BrindleWomen Skechers Go Walk 4 Convertible 14929 /BBK Color Black 100% sneaker New , Baskets Femme samples shoes ETNIES IROFA BLACK RED WOMEN , NEW REEBOK WOMENS WOMEN'S PRINCESS - WIDE DNew Balance Womens Wid626w2 White Walking Shoes Size 6 (358849)Skechers Work ATSP Slip Resistant Womens Grey Athletic Shoes 9M ,
"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."