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.Maria Sharapova By Cole Haan Women's Metallic Leather Ballet Flats US Size 6 BClarks Women's Brown Leather Clog Slip On Casual 7W Closed Toe , Restricted Modcloth Tartan Black Red Green Plaid Leather Ballet Flats 6 Retro , Merrell Womens Suede Fabric Brown Moc Clogs Mules Ortholite Q Form 7.5NIB Clarks Womens Brown 7-1/2 Wide Nikki Auditions bendables Mary Jane shoe , Keds Women's Size 7.5 M Tan Fabric Uppers Athletic Tie Up ShoesFashion Women Men Casual Health Canvas Flat Shoes Cat Cartoon SnowyDark Burgundy Brown CLARKS Unstructured Slip On Lined Perforated Low Shoes 8.5 M , TS shoes TAKING SHAPE sz 9 / 40 Addison Slides wide fit rose gold bling NIB! , Merrell Winter Moc Gunsmoke Suede Womens Slip-On Trail Outdoor Shoes Size 7 , ZARA FLORAL PRINT LOAFERS JACQUARD SIZE 38Munro Womens Brown Leather Flats 11 M , SAS Tripad Comfort Womens Sz 8 Black Leather SneakersWomen's Brighton Artist Black Leather & Patent Loafers w/ Silver Size 8.5 MTory Burch Ballet Flats SZ 6.5 Womens Shoes Suede Slip On , KEDS Women Military Green Sneakers Size US 7/GOLITE Precise Fit “Aura Lite”Walking/Hiking Ballet Style Shoes Women’s Sz 9.5Women?Sport Shoes Fashion Summer Mesh Fabric Travel Shoes Casual Footwear , NIKE REVOLUTION TRAINING RUNNING SHOES - BLACK PURPLE WHITE ( SIZE 10 ) WOMEN`S , Nike DELTA Lite BB Womens Shoes Sz 7 BasketBall 365949-002 Retro Look Black PinkWomen's Vans Old skool cosmic Galaxy Trendy Athletic Shoes , Women Vlado Footwear Shoes Siren Sneakers Red Size 7.5 , NEW VANS AUTHENTIC LO PRO CITY BLACK TRUE WHITE SHOES WOMENS 10 MENS 8.5 VAULTNEW Beloved WOMENS HIGH TOPS SHOES MERYL US 6-12 CUSTOM MADE TO ORDER , Womens Adidas ClimaCool Fresh Ride Running Walk Shoe Purple Sz 6nike dual fusion TR 2 womens running trainers 631459 600 sneakers shoesSPRING COURT - G2 Low-top Women's Midnight Canvas - Sz40 , Vintage Retro 80's 90's Reebok Classics Women's High Top White Shoes Size 8.5Nike Free RN 2017 (Women's). Anthracite/Metallic SilverSkechers Summits Womens Slip On Bungee Sneakers Taupe 8.5 W ,
"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."