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.Bandolino Ferrista Bow Tie Ballet Flats 890, Gold Multi, 9.5 US , G By Guess Crimson Velvet With Bling - Women's Sz US Crimson Ballet Flats NEW! , ELECTRIC KARMA SHOES WOMENS SIZE 7 , NEW ASOS Gold 3 Strap Flat Mary Janes Size 9Merrell Parma Saddle Brown Loafers Shoes Women's Size 6.5 QForm Air Cushion , LAUREN RALPH LAUREN ALICE GIRAFFE PRINT CALF HAIR LEATHER BALLET FLATS SIZE 7.5Nina Klaire Metallic Womens Shoes Size 5.5 M Flats MSRP $79Clarks Wave Wish Slip On - Women's Size 7.5W BlackSperry 7 SEAS Sport Boat Shoes-Women's size 9 M GreyIndigo Rd. Womens irhestley3 Closed Toe Loafers, natural fabric, Size 9.5 M6Fk , NEW Size 6M Womens Keds Baybird Wash Stripe Navy Boat ShoesC20 NEW Mercer Edit Callback White/Silver Leather Low Top Sneakers Women's Sz 10Bandolino Fadri Slip On Ballet Flats , Gold Muti , ASICS Women's Pink & Gray GT-2000 Dynamic Duomax Shoes Sz 7.5 , Girls's Denim Kiss Lips Printed Slip On Cartoon Sneakers Loafer Plimsolls Shoes , New Balance 442 Womens Sneakers Walking Trainer Shoes White brown Blue 9 CW442TFSkechers Skech Knit Women's Sneakers Size 10 Gray Teal Tennis Shoes Flex SolePropet Women's TravelActiv Mary Jane Fashion Sneaker SZ 8.0 WIDE DISPLAY D8285 , Privo Clarks 75572 Slip on Sport Sneakers Womens 8.5 M Brown Leather Pink ShoesSkechers You - Rise Trainers Womens Memory Foam Lifestyle Flats Shoes 14958 , Womens Asics Black/White/Blue Gel Lethal MP6 Turf Shoe, Size 9Size 12 Womens New Balance Fuelcell RUNNING SHOES 1260v7 Lime Glo NEW , NIKE AIR ZOOM PEGASUS 32 WOMENS SHOES ASST SIZES BRAND NEW 749344 001NIB NIKE Womens 8.5 DUALTONE RACER 917682 101 WHITE CASUAL LIFESTYLE SHOES $90NEW WOMENS ADIDAS SUPERSTAR 80'S SHELL TOE BLACK SNAKE LEATHER SIZE 8.5 (BZ0643) , adidas Neo Women's CF Element Race W Running Shoe , Fashion Womens Wedge Heel Sport Shoes Athletic Cozy Ankle Boots Warm Casual ChicMerrell Women's Moab Waterproof Hiking Boot - US 5 and 6.5 Size , ASICS GT-1000 5 Blue;White;Yellow - Womens - Size 5.5 B , Inov-8 Womens All Train 215 Gray Running Shoes Size 7.5 (352910) ,
"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."