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.CLARKS Artisan Tona Summit Brown/ dark Olive Suede Leather Oxfords Womens 9MEasy Spirit Black Hook & Loop Strap Mary Jane Comfort Shoes Size 6WCOLE HAAN Ladies Gold Leather Oxfords Size 7M , Ladies Spot on White synthetic diamante slip on shoes 15901 , Columbia Maatu Women's Brown Leather Insulated Slides Clogs Shoes - US 6 , Womens Ladies Black Stud Flatform Sandals Summer High Wedge Espadrilles ShoesJ Crew Cece Studded Suede Ballet Flats - Anchor Grey - 6Carlos by Carlos Santana Women's Eden Ballet Flat, Sapphire Blue, 6 M USSAS Take Time Brown Leather Moc Toe Diabetic Comfort Oxford Shoes Womens 9.5WWCLARKS 01708 WOMEN'S ASHLAND BLUSH BROWN LEATHER SLIP ON SHOES NEW IN BOX , Propet Women's Ladybug Walking Shoe Oyster Size 11.0 1bMANEW WOMEN'S TEAMCHEER COBRA WHITE CHEER SHOES FWCF801 SIZE 10 , Adidas Climacool Fresh Ride Running Shoes, #V23380, Wht/Blue/Pink, Womens US 8 , Womens Asics Gel Maverick 3 Running Training shoes size 8.5 T077N , Gola Active Salinas Women's Plain All White Lightweight Fitness Trainers New , New Balance Womens 8 M WW565TN Everlight Walking Athletic Zip Shoe Beige LeatherRyka Hydro Sport Water Shoe - Women's size 5.5M - Blue/Gray , ECCO Life Fashion Premiere 38313 Black & Silver Women's Golf Shoes 38 / 7-7.5 USWomen's Nike Womens Blazor Suede VNTG Fashionable And Attractive Packages Athletic ShoesMen's Shoes Slippers BEARPAW Men's Peeta Slipper Easy To Use SlippersWomen's converse all star sneakers Womens Aesthetic Appearance Athletic ShoesLadies Skechers Memory Foam Sports Trainers - Dynamite 12119NIKE WMNS ROSHE ONE LX BLACK LEATHER IVORY Surprise Pack 881202-001 Womens 7Skechers Womens Ultra Flex - Free Spirits 12846 PUR , Skechers Play On Womens Sneakers Black Size 11M , DZ167 CULT US 7 shoes gray pink suede leather women sneakers361 Sensation Purple/Heliotrope/Grey Women's Running Shoes 201510101-2010 , CONVERSE CHUCK TAYLOR ALL STAR OX HI BLACK PURPLE WOMENS SZ 5-9 * 542480F *Katy Perry Womens The Lena White Fashion Sneakers 9.5 Medium (B,M) BHFO 9256Asics Size 6 Pink Running Sneakers New Womens Shoes ,
"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."