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.Sanita Red Suede Comfort Slip On Clogs-Size 7-7.5-Cute and Comfort! , Haband Size 9 M Blue White Womens Shoes Walking Shoes , London Sole Women's Ballet Flats Size 39 9 White Brown Faux Fur Zebra PrintVince Camuto Black Perforated Suede Loafers - Size 7.5Clarks Sillian Jetay Slip On Shoe - Women's Size 11M, BlackKenneth Cole REACTION Women's Jet Ahead Dress Tassel Black/Multi Size 6.0 , BCBGeneration Sabrina Flat Mules 646, Brown Multi, 6 US / 36 EU , Women's Chinese Ethnic Embroidery Flat Elevator Cheongsam Dress Shoes Bamboo , BareTraps Mitsy Hidden Wedge Flats 992, Black, 7 US , Aetrex 8 Lizzy Black Mary Jane New in Box , Klogs Natalie Women's Clogs Display Model Shoes Brown JW Floral 8 M , MERRELL Women's Sz 6.5 W Barrado Black Sport Zip-Top Closure Slip-On ShoesWomens Fergie NIB Benny Orange Flats 9 M , Donald J Pliner Beige Flat Slides - 7.5MKS35 Flura Flat Loafers, Navy, 10 US , WOMEN'S sz 9 New Balance 670V2 RUNNING SHOES - GREY YELLOW WOMEN'S Abzorb 670 v2 , Rockport $90 MEN SHOES SLIPPERS Suede Moccasin Slippers SIZE 11 Brown SALE P16 , WOMEN'S UNDER ARMOUR SPINE VICE ATHLETIC RUNNING SHOES 1238604-443 BLUE SIZE 8 , Salomon XR Shift Women's Trail Running Shoes Size 7.5ATELJE 71 Black Emery Textured Leather Slip-On Sneakers Shoe Size 8 , Hoka One One Women’s Running Shoe Bondi B Size 6.5 Work Hubble CushionVANS ISO Moc Monks Robe Brown Suede ULTRACUSH MEN'S 8 WOMEN'S 9.5NIKE Womens Tanjun Racer Running Shoe (7.5 B(M) US, Cool Grey/Sail-Black) , 361 Women's Voltar-W Running Shoe, Gray/Spice, 9 M USAQUA Women's Foxy Slip-On Sneakers Size 8 Black , Skechers Sport Women's Women's Skech Air 2.0 Next Chapter, Black/White, Size 7.5 , VANS Black Ball SF Black/White Casual Shoes WOMEN'S 9.5adidas ZX Flux - Multi - WomensNike Kaishi GS Running Shoes Pink White Youth Sz 7 = Womens Sz 8.5 705492 600Converse All Star Women's CT OX Digital Floral Multi High Top Sneakers- 6.5 NWOB ,
"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."