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.WOMAN’S CROCS 15375 DUET BUSY DAY BALLET SPORT ATHLEIC FLATS GRAY 8 EUC SLIP ON , Minnetonka women's 5 moccasin soft leather bottom Halloween Pocahontas Indian , Down to Earth F10429 Beige/ Gold Ladies Sandal (R7B)SAS Siesta Tan Leather Comfort Moc Toe Casual Loafer Shoes Womens Sz 6.5 M , Lucky Brand Emmie Women 6.5 M Shoes Multi Color Chevron Ballet Flats , Clarks Privo Shoes Sz 6 Loafers Brown & Bronze Slip-On Sports Sneaker , DREAM PAIRS KAIYA_01 Women's Adventurous Summer Outdoor Sports Flats SandalsICON Women's Shoes WEARABLE ART Size 7 Made in USAJ.Renee Womens edlyn Closed Toe Loafers Black Size 6.5 , Sam Edelman Shoes Womens Size 9 Becker Slip On Woven Black White Print NIBKlogs Women's Clogs Display Model Shoes Mackie Black Eagle 6.5 MMIU MIU Casual Shoes, Brown/Olive, Womens US Size ~8, , Tods brown suede penny loafer flats. size 6.5Clarks Sandals 8.5 Black Leather Slides Shoes Heels Women'sDakota Quad Lite Steel Toe Steel Plate Women's Grey/Black Sneakers 6.5M , Womens Chic Mules Shoes Embroidery Slippers fashion Leather Loafers backless , Nike Air Twilight Women Black Pink Athletic Shoes Sneakers 325255-061 Sz 10Stylish Ladies Hollow Out Slip On Hidden Wedge loafers Atheltic Sneakers PumpsSuperga 2210 COTW Slip-On Sneaker, Women's Size 8.5, BlackConverse Fashion Sneakers Black Textile Women7Medium (B, M)Tretorn Nylite 15 Plus Sneaker, Women's Size 7.5, White/NavyNew Balance Womens WZANTSI3 Running, Cross Training Shoes 6 Medium (B,M) 6411Skechers Street Women's Darma-Perforated Leather SneakerASICS Gel-Contend 4 Ortholite Gray Silver Purple Navy blue Size: 11 NEW! , Womens ADIDAS HARD COURT HI W Black Pink Synthetic Trainers Q21305K-Swiss Women's Belmont SO T Sherbet Fashion Sneakers (6.5 B(M) US)VANS New SK8-Hi Reissue DX Tiles Vault Lady size USA 7 , PUMA Women's Basket Metallic Platform Sneakers, Gold, Size 8.5 - / RX29/30 , PUMA WOMENS DARE WNS SPECKLES FASHION/CASUAL SHOES [365252 01]Women's Nike Air Navy and Mettalic Baby Pink Tennis Shoes Size 8.5 ,
"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."