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 COLLECTION Womens Loafers Brown Croc Print Slip On Shoes Sz 7 MSperry top sider animal prt boat shoes size 9 , BareTraps Hastings Mary Jane Comfort Flats, Black, 7.5 M USIndian Women Shoes Designer Jutti Handmade Flip-Flops Ballerinas Mojari US 5-10Massimo Matteo Penny Keeper Leather Loafers, Women's Size 8B, White , Jutti Indian Women Shoes Leather Handmade Mojaries Oxfords Flip-Flops US 6-12SPERRY Top-Sider Women Boat Shoes Size 10 M Brown Suede , 100% new handmade genuine leather men's boys ladies women footwear shoe loafers , Skechers Women's Reggae Fest - Willows (Wide) Casual ShoeCC Resorts shoes cloud comfort elastic SLIP ON walking shoe Sugar - 7 coloursWomen Pointy Toe Flat Fur Lined Warm Slip On Casual Shoes Leather Loafer Chic , Stuart Weitzman Women's Metallic Gray Leather Slip-on Flat Size 6.5MPropet Therapeutic Black Women's Comfort Shoes Double Strap Size 8W Wide WPRX08Vans women shoes sized 9.5. Brand new! , Adidas Women's Basketball Top Court G66216 Size-9 , Asics GEL-Excite 2 women's 10 Onyx-DivaPink-Mint T473N running shoes trainersVTG Women's Nike Tiempo Leather Shoes 10.5 Black White Pink 454337-016 EXC! , Saucony "Excursion TR 5" Silver and Lite Green Running Shoes Women's 9Ryka Hydro Sport Sneakers-Women's size 6.5 M Silver , adidas Instinct - Black - WomensSALOMON X-MISSION 2 Womens Trail Running Shoes Sneakers Blue Purple US-8MNew Womens Nike SF AF1 MID Special Forces Shoes Air Force 1 AA3966-002 sz 9 , NIKE WOMEN'S PRESTO FLY SE SHOES neutral olive 910570 200 MSRP $110 , Original Vans Old Skool VN000D3HW00 White Canvas Casual WOMEN , Skechers Women's Vita Vivere Fashion SneakerNike Lunarglide 3+ LX Liu Xiang Pack Shoes Spirit Red Orange SZ 5 ( 454312-606 )Adidas Falcon Women Golf Sneakers ShoesNEW Merrell Women's Kamori Breeze Casual Slip On Shoes, Black, Size 6Hoka One One Clifton 3 Running Shoes sz 9.5 (US) Blue Jewel Neon Coral WomensConverse Chuck Taylor All Star Shoreline Women's Slip-On Shoe 537082F Size 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."