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.Hogl women Shoes ballet flats Beige pink Patent Leather 37Beige Flats Great Work Work Sz 8 NEW COMFY tie Knot Of Feont CUUUTE !! LEATHER , LADIES ORONZO LOW WEDGE ELASTICATED SLIP ON CASUAL CUT OUT SHOES WLF89319*NEW* Hush Puppies Red Leather Mary Jane Comfort Shoes Women's Size: 7.5 W , Womens Merrell Bicore ECLIPS SZ 6 Loafers Work Brown Slip on Clogs Leather ShoesFranco Sarto L Baylor Womens 9.5 M Black Slip On Loafer Brown Low Heel MSRP $99 , women's shoes OLGA RUBINI 7 () moccasins slip on blue paillettes BX787-37ALEGRIA BEL-442 BELLE TOTEM MULTI-COLOR PATTERN MARY JANE SHOES WOMEN'S 40Tom's Women's Slip on shoe Brown Suede Size 5.5 , Spelta Milano "Penelope" Flats with Ankle Straps SZ 7 & 9 , New Womens Embroidery Bee Round Toe Casual Bowknot Loafers Slippers Mules ShoesHOTTER Purple Sneaker Comfort STAR Purple Pink Casual Shoe US 8.5 Excellent , Propet Tour Walker Strap Shoes 3902 Taupe Size7.5 D(w) Adult , Skechers Womens - Blue Fashion Shoes Size 9 (362159)Women's Under Armour Contender III MC Cleats - Black/White - NIB!Skechers Skecher Street Womens Darma-Perforated Leather SneakerC&A Red Satin Knot Bow Fashion Sneakers US 6Altra Shoes Zero Drop WomensYouth Size 3.5 girls running sneakers shoes , Women's woman sneackers The King Of Quantity Athletic Shoes , Women's Born Black Leather Shoes 6.5/37 Quality And Quantity Assured Flats , EUC VINTAGE 2000 NIKE AIR MAX WHITE US 9 WOMENS 605166 061 RARESkechers Womens Flex Appeal 2.0 Bungee Slip On Shoe, Black/Charcoal/Lavender, 6 , NIKE Womens Size 9 ‘FLEX 2016 RN' Running Shoes Gray/Mint NWBWomens NIKE ROSHERUN Pink Running Trainers 511882 467Women's Vintage 1997 White & Blue NIKE AIR High Tops Basketball Sneakers Sz-8.5 , NEW Red All Star Plaid CONVERSE CHUCK TAYLOR Low Top Sneakers Women's Shoes 7Womens Nike Shox Reveal 3 gray/red running training shoes sz 9Merrell Women's Freestyle Dune Camo Green Walking Hiking No Slip Shoes Size 7 , NEW WOMEN'S SAUCONY PROGRID HURRICANE 13 WHT/SIL/GRN RUNNING SHOES 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."