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.Women's Teva Kiru Gray Nubuck Leather Slip On Sneakers Size 6 , LC Lauren Conrad Sky Blue Floral Flats. Size 8. , � Lands' End Slip Comfort Slip Ons size 8.5 M Hot Pink Canvas , Aerosoles BRIGHT Multi-Color SHOES WOMEN'S SIZE 11Elizabeth and James Black Leather Stretch Fit Ballet Flat Shoes Size 8 , Via Spiga Womens Loafers Size 7M Beige Suede Oxfords , Nordstrom BP 'Lodi' yellow round toe leather perforated slip on ballet flats 7M , Easy Street Purpose Slip-On Flats, Black Patent Croc, 7.5 WW USModa Spana Black Flats Shoes w/ Studs faux LEATHER sz 7.5 M WORN 2x MINT L@@K!!!SAS women's orthopaedic diabetic shoes wedge heel size 8M silver great condition , Black Leather Umberto Raffini Shoes 38, 7.5 New in Box , aerosole flats with elastic criss cross details , Bolo NWOB Womens Animal Print Flat Clog Shoes 6.5M Brown Occupational Wood HeelANDRE Ballerines Toile rigide Tressée Beige T 38 TTBE , BOUTIQUE 9 STUDDED BLACK LEATHER FLATS WOMEN'S size US 10M HOT , Munro Brandi Ballet Flats - Women's Size 7.5 N - RedSteve Madden SICILY Slide Flats Sandals Black Women Size 8New FIERAMOSCA $225 High-End Suede Loafers Shoes CHROME Detail MADE in ITALY 7NGabor 6.5 Womens Comfort Shoes Brown Leather Mocs Loafers Slip Ons , Red Multi Fashion Sneakers Sporty Slip On Button Womens Ankle Booties Shoes , Cole Haan Women's Slip On Loafer Justina Dk Chocolate Brown Leather Sz 7B (U2)Nike Shox Cognescenti Woman’s Size 8 Silver And Purple Shoes Tennis Running , Skechers 50875 ROCKERS CHARCOAL GREY BLACK LEATHER SUEDE WOMENS 8 8.5 M EUCADIDAS Women's Cloudfoam Advantage Stripe Athletic Comfort Sneakers True to size , ASICS GEL LYTE III GREEN GREEN WOMEN'S RUNNING SHOES 100% AUTHENTICTeva Womens W Freewheel Washed Canvas Slipper- Pick SZ/Color. , Clarks Everlay Coda Black US Size 5.5 M - FREE SHIPPING - BRAND NEWWomen's Nike Zoom Streak 6 Racing Shoes Electro Green Size 8 831413 303 NIBSKECHERS WOMENS ORBIT FASHION SNEAKERS 23351/BKCC , REMONTE caramel brown soft leather comfort walking loafers wedge shoes 41 US 10
"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."