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.Merrell Arabesque Womens 8 M Gunsmoke Grey Leather Zip Up Qform Comfort ShoesSoda Slip On Mules Chunky Punk Grunge Doc Martin Look Black Size 6-6.5 , Clarks Artisan Candra Glow Purple Grey Suede Violet Ballet Flats Women's US 6 M , Womens Clarks Size 9 1/2 Slip On ShoesSoft Style by Hush Puppies Women's Faeth Flat, Bronze Vintage, 6 M USSplendid Jaime Brown Womens Shoes Size 6.5 M Flats MSRP $98FILA "DLS" LEATHER RUNNING/CROSS TRAINING.....SIZE: 6.5......EXCELLENT CONDITION , Adidas Womens Energy Cloud V White Running Shoes Size 7 (5835)Puma Leadcat Botanical Navy - Womens - Size 9.5 BSalming Distance A2 Women's Premium Performance Running Shoes Trainers BlackRyka Free Lance Tie Ltt Women's ShoesAdidas Cloudfoam CF QTFLEX W Women’s Size 10 Running Shoes. Light Blue. NWTNew Vintage Nike WMNS Sprint Sister Lavender Pink Limited 311853-661 Size 7.5 , Circus by Sam Edelman Women's Collins-3 Sneaker - Choose SZ/ColorWomen's tory burch shoes size 5.5 Quality And Quantity Assured Flats , Women Converse Chuck Taylor Dainty Metallic Leather Low Top, 553336C Sizes 6-10Asics Gel Kayano 24 Size US 9.5 M (B) Women's Running Shoes Blue T799NENZO ANGIOLINI CASIANO Pink Man Made Designer Pumps Heels 6.0 M , Nike Women's Air Zoom Pegasus 34 Running Shoes Blue Fox Crimson 880560-403 Sz 12Womens Skechers Go Flex Yoga Workout Walking Fitness Running Sneakers US 6-11 , Women's Custom Atlanta Falcons Football Red Black Silver Glittered Tennis ShoesPUMA CELL KINETIC TRAINER SHOES WOMEN'S SIZE 11 , adidas NEO Cloudfoam Advantage Stripe Women's Shoes Iridescent White Size 8 , Womens Nike Free TR Fit 4 running shoes size 7.5 black print excellent conditionNew Converse All Star Chuck Taylor Ct 70 Ox unisex Mens 4 Womens 6 NaturalNIKE AIR FORCE XXV CLOVERDALE PARK SIZE US 12 NICE SALE , Ryka Hypnotic Running Training Fitness Athletic Shoes Sneakers Green Womens 10 , WOMENS ED HARDY SHOES SZ 9 M , Nine West Women's Sophie Suede Fashion Sneaker, Black/Multi, Size 10.0 , Kaanas Womens Sneakers Size 7 Sahara Sand Leather MSRP $109 NEW IN BOX ,
"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."