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.Minnetonka Moccasins Slip On Shoes Brown Suede Size 6.5 , Kenneth Cole Reaction Embellished Bead Thong Flip Flops Sandals Flats Shoes 11 M , Avon MARK Emerald Princess PUMPS Shoes Sz 9 Women/Juniors. NEW! NIB. GREEN , Dolce Vita Brown Black Calf Hair Hide Zebra Print Flats Oxfords Shoes Sz 6COLDWATER CREEK Wedges Mary Janes Ballet Flats Clogs Loafers Womens Shoes Sz 8 , Minnetonka Red Fringe Tie Thunderbird Beaded Moccasins Women’s Sze 7 Barely Worn , crocs Crocs Womens Lina Ballet Flat- Select SZ/Color. , Born Concepts Womans Sandals SZ 9 Platform Leather Strap Peep Open ToeWomens 9 M Merrell Ceylon Sport Ballet Flat Shoes Castle Rock Gray Slip-On Wedge , Dansko Brown Suede Clogs Mary Jane Mule US 6 Strap BuckleAttilio Giusti Leombruni Cap Toe Women's Black Dress Flat 37.5 EU/7.5M US , Seychelles Latest Flat - Women's Size 6, Nude , NIKE FREE 5.0 PURPLE RED 7Y or WMNS 8 NICE USED CLEAN WORN see pics-details , Simple Hallie Clogs Womens 7M Taupe Mule Shoes Suede Walking Casual Comfort NEWShellys London Emma Silver Citadel Platform Women's Shoes Size 36 US 7 MWomen's 9.5 Nike Shox M1 Athletic Running Shoes Black Pink Gray 347771-003Vans Women Surf Shoes Solana Leila Deep Blue Purple White Shoes 5.5 Canvas Sk8Kim & Zozi Plaid Women's Hi Top Shoe - Women's Size 10, Blue , New Women Crisscross Stitch Fashion Sneakers Heel Medium Cotton 100%_White BlackNew Womens Skechers EZ Flex 2-RIGHT ON FASHION Sneaker in Charcoal 22698 A50Merrell Women's Size 9.5 Hiking Shoes black purple water resistance slip onWomen's osiris nyc 83 Promotions Athletic Shoes , Converse Black Canvas Hi-Rise 9-Eye Ankle Calf Boots / Shoes Wms NWOT DISC , Labrador Retriever On Deep Skyblue Print Shoes For Women- Free ShippingBetsey Johnson Darbi Fashion Sneakers, Blush SatinFila Womens Memory Foam Outreach Athletic Shoe 9 GreySaucony Women's Grid Ideal running Shoe - Choose SZ/ColorWOMENS DC CHELSEA SE SKATEBOARDING SHOES BLACK BLACK (BB2) , Asics GT-2000 4 Women's Sz 7.5 Silver Athletic Running Training Shoes ZU-1324 , Avia Women's 344 Slip Resistant Ankle-High Training 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."