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.SAS Tripad Comfort blue leather penny loafers slip ons Women's shoes size 7 SEspadrilles woman girl stripes canvas sewn hand sole rubber cord/ rope , Aerosoles Women's Trust Fund Slip On Loafer, White Leather, 8 M USED Ellen DeGeneres Womens Darja White Casual Shoes 6.5 Medium (B,M) BHFO 1345 , NATURALIZER N5 Comfort ~ "Malvina" Black Leather Loafers Sz 8M * VERY GOODHelle 6 Burgundy Alligator Loafers , Sperry Womens Quest Rhythm Gray Boat Shoes Sneakers 9.5 Medium (B,M) BHFO 7098MARVIN K. Womens Suede Ballet Flat Shoes Sz 9.5 , Clarks Collection Loafer Soft Cushion Casual Brown Women Shoes US 8 M , New $129 MARC FISHER Purple-wine Sunny Half D'Orsay Flats 7 , Tommy Hilfiger Frank 3 Slip On Sneakers, Women's Size 6 M, WhiteNIKE Air Citius +2 Yellow/Silver/Gray Running Shoes Women's Size 8.5Brooks Launch Women's 7.5 Running Shoe Red / Grey 1200601 B678NWT Men's Saddlebred Micro Suede Clog Slippers with indoor outdoor sole S 7-8 , Acorn Fave Gore Slipper - Men's Charcoal Tweed LSKECHERS Women's Shape -Ups Training Sneakers White & Blue Size 7 SN 12320 , Womens Very High Heels 11cm Zip Fashion Casual Sports Shoes Rose Red New A537 , Puma Women's Shoes Size 9 Silver , NIKE 749351 830 Zoom Rival XC Cross Country Cleat TANGERINE/LIME RACING 11.5 ANBNike 'Free Connect' Training Shoe- Black- Size 7- $100.00 , Adidas Women's Alphabounce Rc Running Shoe , Nike Revolution 4 Womens 908999-004 Gunsmoke Ocean Bliss Running Shoes Size 10Skechers Sport Women's Scene Stealer Fashion Sneaker , Reebok ZQuick Electrify M43726 BRAND NEW!!! Mesh Running Women Shoes , New Balance WW980TN - Women's 980 Leather Walking Shoes , NEW Women's Nike AKAMAI sz 5.5 CRIMSON ORANGE White Black Spikeless Golf Shoes , Womens Converse Chuck Taylor All Star Denim Floral Blue White 555976FCole Haan Pale Pink Slip On Slide Sneakers Sz 7.5AA , Easy Spirit Travelport Slip on Sneakers Athletic Clogs Tan Striped Women Size 11NIB - VANS Women's 'WARD HI' Red SKATER SHOES - 11.5 / 45
"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."