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.Betsey Johnson Womens Hazyl B/W Espadrilles Shoes 6 Medium (B,M) BHFO 8996 , hush puppies womens loafers Size 7 NewDansko Sz 41 US 10.5-11 Arden Clogs Brown Leather Slip On Loafers Shoes , Report Women's Marni Ballet Flat Black Size 6.5NWOB Womens EASY SPIRIT Anti-Gravity Slip On Comfort Shoe Fabric Black 7.5N , Sloggers 5113BP07 Rain&Garden Shoe, Wo's Size7,Black/White Polka Dot PrintSperry Top-Sider Womens 11m Pink Plaid Boat Shoe Flat Leather Tan Non MarkingLands End Women Front Zip Comfort Loafers Shoe Lt Blue Suede Quilted Top 10B New , New Arturo Chiang Espadrille Moccasins Leather Women Shoes Beaded Off White 6 , VANELi Womens Nadette Slip-On Loafer, Cuoio Nabuk, 8.5 W US , Dr. Martens POLINA 4 hole wing chip shoes UK6 NO. 1499ko * *CHACO Toe Coop Womens Size 9.5 Brown Nubuck Leather Adjustable Strap Slingbacks , Comfortiva Womens grace Closed Toe Slide Flats, Black, Size 8.5 FNkT , Platinum By Jade 12235 Wide Width Ballet Flats Choose Sz/Coor , Womens North Face Brown And Yellow Linen Shoes 7.5Howsty x Anthropologie Womens Taizz Espadrilles Shoes Black White Size 39 NewWomens Hip Hop Sneakers Casual Patent Leather Breath Sports Shoes Flats New size , Keen Womens Malibu Mary Jane Trail Running Shoes 6.5 Hiking WalkingAsics Gel Noosa Tri 9 Running Triathlon Shoes Multi Color C401N Womens Sz 6 A2VANS Tazie SF Gossamer Green White Casual Shoes WOMEN'S SIZE 9ASICS Gel Contend 3 Womens Sz US 6.5 Running Walking Athletic Shoes (11G)VANS UNISEX TENNIS SHOES MEN US 8.5 WOMAN US 10 Glitter Sparkle Purple multicoloWomen's Sperry Top-Sider Crest Buoy Sneaker Customers First Athletic Shoes , K-Swiss 95578-040-M Womens Gen-K Icon Knit Sneaker- Choose SZ/Color. , PUMA Basket Heart Women's Tibetan Red/Tibetan Red 36307305 , Nike Flex Supreme TR 4 Women's Cross Training Shoe 819026 003 Size 6Reebok Women's Trainfusion Nine 3.0 Cross Trainer, Cloud Grey/White/Digital, 9 M , REEBOK CROSSFIT NANO 3.0 CF74 WOMEN'S ATHLETIC SHOES SIZE 7.5 PINK V53246 , Nike Air Max 1 Ultra Moire Athletic Running Shoes White Gray Womens 8 , Easy Street Womens Barbara Low Top Slip On Fashion White-floral Size 10.0 7khG
"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."