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.Onitsuka Tiger Women's Kanoka Pink/Pink, Flats 7M , Dockers Melvin Suede MJ Casual Shoes, Black, Women's US Size 9.5 , Sex Pistols Dorothy Women's Flats Punk Goth Shoes NEWMUNRO American Size 5.5 M Black Leather TOP Zip- Low-Heel Slip-On Loafers , Women’s 8½M Born Ballet Flats Metallic Bronze Brown Leather ½” Heels Very GoodCole Haan Women's Black Patent Leather Rodeo Penny Loafer Driving Shoe Size 8Sperry Top Sider Women’s 9518788 Navy Leather Boat Shoe Size US 6.5M , Womens Naturalizer Veneto Size 9.5M Brown Leather SlipOn Loafers Driving Moc-316Clarks Bayou Black Leather & Croc Emobossed Loafers Flats 8 Sale R , SUPERGA Cotu Women’s Pale Sand Greyish Fabric Classic Canvas Sneakers US 7 C279 , Sperry Top Sider Women's PINK Nubuck Reptile Embossed Leather Boat Shoes sz 8Easy Street Womens Barbara Low Top Slip On Fashion White flower Size 12.0 EIlD , Asics Gel Kayano 19 womens running shoe 10.5 original soles **flaw** Black PinkWomen's Nurse Mates Mule type comfort shoes Size 10 M Brown Leather Exc Conditio , GOLA Quota size 6 women or 37eu NEW Union Jack Low Cut Athletic Sneakers , Vintage Distressed and Aged VON DUTCH Women's Hi Top Orange Sneakers Size 8 , Apex Silver Blue Athletic Running Walking Tennis Shoes 10.5WW , Merrell Enlighten Shine Castle Rock Sneakers Womens sz 7 Casual walking shoes , 02-823 Skechers 12794-BKGD Women's Burst Black Gold Oxford SIZE 9Brooks GTS 15 Blue/Purple/Citron Running Shoes Women's US Size 8.5 , Women's Skechers Relaxed Fit Endeavor Atmosphere Slip On Shoes Brown Size 6.5Skechers Women's Flex Appeal 2.0 - Passports White/Gray Loafers & Slip-Ons ShoeNike Air Max Sequent 2 Sneaker - Women's Size 8.5 PinkNike Flex Adapt Women's Training Shoe - US 6.5 - Grey/Pink - MF , REEBOK CLASSIC JOGGER J95481 WOMEN'S BLACK/PINK SHOES SIZE 5.5 , Nike Lunarglide 8 Running Shoe- Women's US 9.5 Medium Blue , New Sperry STS82406 Crest Vibe Metallic Silver Women's Boat Shoes 6.5 US , Original Kitson Diva Buttons 34530 PKRD Pink Casual Women Shoes , New Balance 920 Running Shoes Women’s Size 6 B US Near Mint ConditionSkechers Women's Bikers-Curbed Sneaker, Black, Size 5.0 ,
"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."