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.LifeStride Women's Fantell Ballet Flat Mushroom Size 7.0 , Women’s 8M Loafers Flats Munro American Burgundy Leather Shoes ¼” Heel ExcellentTom's University Navy Women's Canvas Slip-On - Size 9Merrell Marina Shoes Flats Size 6 Vibram Ivory Leather Driving Moccasin BoatWorx by Red Wing Clogs Mint Size 8.5 M WomenClarks Artisan Womens Shoes Strapless Slip On Clogs , Naturalizer Rowan Women's US Size 6.5 Medium Black Loafers ShoesBlack Eject Ankle Strap Flats 6.5 37KLOGS SPOKAN CLOGS DISPLAY MODEL SHOESCHESTNUT 14 WCarlos Santana Beaded Thong Sandals Wedge 6.5M Apache Ladies Platform Flip FlopEcco Womens Size 38 Mary Jane Loafers Casual Shoes (Q) , CL by Laundry Sherilyn Shoes Size 8.5 M Flats Champagne Glitter Rhinestones , Kenneth Cole New York Womens Kam Ballet Leather Closed Toe Light Gold Size 6.5 , BNWT ZARA BLUE FLAT PLATFORM BLUCHER SHOES REF.3260/101Clarks Cloudstepper Caddell Yale Black Mary Jane Style Wedge Heel Shoe Sz 8 , Women's Skechers Shape-Ups XF Energy Blast Shoes 8 Black Walking , Converse Hi Tops Trainers Sneakers Vintage Unisex Grey US 8.5Women Nike Zoom Rival S Track Spikes Black, Silver Shoes 9.5 Excellent Condition , Keds Mary Jane Casual Sneakers, Tan, Womens US Size 8.5 , WOMEN'S Babolat Propulse LADY 3 (BLACK / PINK) SZ 9.5 TENNIS SHOES. 31S1274 , Skechers Performance GO walk 3 Slip On Shoes, Women's Size 6.5, Black/PinkWomen's Converse Chuck Taylor Ox Casual Shoes Black W9166 BLK SZ 6.0 M M952Women's Navy Leather Beaded Minnetonka Mocassins Fashionable Patterns FlatsNew Nike Womens NikeLab Running Shoes Free Run Motion FK 2017 883292-100 sz 7 , ASICS Womens Gel-Contend 2 Running Shoe,White/Turquoise/Sharp Green SIZE 6 , New Balance Womens Wx811 Training Shoe-W Black/Silver Running Shoes Size 6.5 , Puma Suede Platform Gold - Black - Womens , NEW! Skechers Women's SKECH AIR 2.0 CITY LOVE Shoes Black/Pink Q az , NIKE AIR REGRIND 970810 Women’s Leather Athletic Shoes US 7 , MBT Chapa Stone Leather Physiological Active Women's Toning Walking Shoes 7.5 N ,
"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."