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.Cole Haan Tali Lock Moc II Beige Patent Leather DRIVING Loafers Shoes SZ 8Soft Style by Hush Puppies Womens Pleats B With U Leopard Shoe HSS1097 6 M , Reba Womens Fleur De Lis Black Suede Loafer Flats Sz 7.5MNEW Merona Women's Aimi Scrunch Ballet Flats Animal Print Black Captoe Sz 8 , Dr Comfort Betty Brown Leather Comfort Diabetic Loafers Women's US 7.5 MDANSKO Vegan Volley White Green Leather Slip on Clogs US 11Womens Size 8 Merrell Zodiac Golden Taupe Leather Shoes , Genuine Leather Shoes Woman Fashion Butterfly-knot Women Casual Soft Flat ShoesEverlane Leather Street Shoe, White, Made in Italy Size 5.5 MSkechers Stardust Follow Me Womens Memory Foam Shoes/Slip Ons/ComfortableWomen's NAOT Rongo Gold Heel Strap Mary Janes US 8 , CHARLES & KEITH blue platform slingbacks - size 37, $199 NEW!!Adidas Women's Neo Lite Cloudfoam Racer Slip On Shoes Gray Size 9CONVERSE SZ 8 CHUCK TAYLOR ALL STARS OPTICAL WHITE CANVAS OX LOW SNEAKER W7652Nike Zoom Rival Women's Track Shoes Size 10 US Sprint Spikes Purple Gray/black , Tretorn Matchhi3 High Top Fashion Sneakers 020, New Dark Sand/New Dark Sand, 7 , ASICS Women's GT-2000 4 Running Shoe Size 8 1/2 , Skechers Women's Performance Go Step Stylish Chocolate 14445/CHOC , Sperry Top-Sider $90 Women's Boat Shoes Size 10 Leather Tan , Aerosoles Pantheon Black Leather/Textile Low Wedge Slip On SneakersNew Balance Fresh Foam 1080v8 Running Shoes-Women's size 10.5(2A) Blue , Bully Kutta/Alangu Mastiff Dog Running Shoes For Women-Free Shipping , New Montrail Womens Trans Alps Gray Running Shoes Size 10.5 , Skechers 780 Skecher Street Womens Utopia-Secrets Fashion SneakerCole Haan Womens Musettesam Low Top Slip On Fashion Sneakers, Purple, Size 6.0Sanuk Donna Hemp Sidewalk Surfer - Olive Grey - NewDiadora SPEED BLUSHIELD CLAY - Blue - Womens , ADIDAS VIGOR BOUNCE W GREEN WHITE B42768 ORIGINALS RUNNING WOMEN'S SIZE 6.5 WOB , Women's Astral Loyak - Navy Blue size 10 - New in box - Never been wornDVS KNOX Womens Skate Shoes (NEW) Sizes 7-11 GIRLS Heather Grey Knit : FREE SHIP ,
"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."