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.KLOGS USA Rust Brown Leather Nurse Orthotics Mary Jane Loafers Flats Women's~7 M , Me Too Drew 2 Black Women Ballet Flats 61/2M Shoes , BORN WOMENS RED WOVEN LEATHER MULES CLOGS Sz 36.5/6Keen Womens Mary Janes Shoes Size 7 , Ladies canvas espadrilles / pumps with side stripesJ Crew Anya Cap Toe Ballet Flats Black Leather Round Toe Size 5.5 , MERRELL "Sailix Ballet" Slip On Loafer Shoes Tan Leather Women's Sz 9.5 , Taryn Rose Womens Kristine Suede Closed Toe Loafers Poppy Size 10.0 , Dr. Scholl's Hadley LS Faux Leather Slip On Shoes, Women's Size 7 M, Taupe , BOC Born Concepts Women's Clogs Mules Brown Leather Print Size 8 , Giovanna Womens Leather Red Hook & Loop Slip On Fashion Sneaker Casual Shoe 8.5M , Zee Alexis Womens Norah Shoes Navy 7.5 M , NIB Amelia Grace "AG Florence" Sz 6 Red Beaded Fabric Ballet Flats , AGL Womens Brown Suede Leather Ballet Flats Cap Toe Snake Print Eur 38 US 8.5 , Frye Kira Women's Brown Perforated Leather Fashion Slip On Sneakers Size 7.5 M , WOMEN'S K-SWISS BLACK SNEAKERS SHOES M LOW/SIZE:6 , 70`S VINTAGE ADIDAS INDOOR SUPER II SPORT SHOES 80`S HANDBALL VOLLEY TT SUPERMerrell Women's All Out Charge Trail Running Shoe Blue Size 7M , Skechers Sport Trail Low Top Hiking Leather Sneakers Womens Sz 7 Gray & NavyRyka Womens Vida Rzx Black Cross Training Shoes Size 8.5 (21686)MIZUNO Wave Paradox 2 Women’s Athletic Running Shoes Silver Teal Grey Sz 8Women's NEW REEBOK WOMENS CLASSIC LEATHER Low-priced Athletic ShoesNike W AF1 Upstep Premium Metallic Platinum 917590-001 Women's Shoes Size 7.5DISNEY VILLAINS 2 inspired CUSTOM HAND PAINTED HIGH TOPS MADE TO ORDERPuma x Minions Collection ST Runner V PS Blue Yellow Kids Preschool 364017-01 , New Balance Womens 696 Faux Leather Mini Dot Running Shoes Sneakers BHFO 9804 , Brooks Ravenna Sneaker - Women's Size 11B Gray/Purple , Ricosta Womans All Weather Sneakers Walkers Size 37 US NWD PINK LBFO , adidas CrazyTrain Cloudfoam - Black - Womens , New Balance Minimus 20 Trail V2 Women's Size 9.5 B Athletic Running Shoes Green
"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."