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.SKECHERS Women Medium Brown Suede Faux Fur Chunky Clogs Mules US sz 7.5 , 02-2034 Bernie Mev Women's TW102 SIZE 7.5Kenneth Cole Reaction Dress Shoes/Flats Size 4.5YBrown W Faux Stones.BOC Born Concept Wedges Mary Janes Ballet Flats Clogs Loafers Women Shoes Sz 6 ~Ladies Spot On Flat Shoes Style - F8439 , Rajasthani Handmade Tassel Women's Ethnic Stylish Mojari Flat Sandals Sleeper S , Aerosoles Good Times Dress Flats 821, Black, 9.5 USGentle Souls By Kenneth Cole • Essex • Women's 10 M Black Leather slip onsSperry Top Sider Womens Slip On Shoes Navy/white Size 9 , MUNRO American Women Moc-Toe Penny Loafer Size 9.5 W Brown SuedeClarks Snakeskin Heels Womens Size 5.5M Black Leather Pumps , AMALFI Rangoni Siry Oxford Suede Burnt Yellow Vintage Shoes Florence Italy 3.5 , Woman Plus Size Crystal Flat Shoes Comfortable Rhinestone Soft Butterfly ShoesNew CIRCUS BY SAM EDELMAN Celyn Studded black Ballet Flats shoes , Designer STELLA MCCARTNEY Morgana Oxford Loafers Slippers Womens RRP$670Nine West Position Tassel Loafers, Pewter, 8.5 US Display , NIB CORSO COMO Gold Metallic Leather Flat Perforated Detail Sz 10 120127LRLa Redoute Collections Womens Ballet Pumps With Twisted Detail , Birkis Birkenstock Shoes Size 39 8 N Provence Birkibuc Mules Clogs Berry Red , SKECHERS 11806 Shape Ups Navy Silver Action Packed Athletic Shoes Women's 8MWomen's Brooks Ghost 7 Hawaiian Blue/Eclipse/Lime Punch Running Shoes Sz 9 M , New Womens Fila Athletic Sneakers Shoes 5SR20098-089 Size 8.5 (US) , Skechers Earth Fest Upcycle Slip-On Women's Shoes , New Nike womens Free Run Commuter 17 Utility running shoes sneakers MSRP $120KEEN Koven WP Womens Gray / Orange Leather Hiking Shoes Size US 5 US / , MBT Women's Afiya Slip-On Red White Athletic Shoe Authenticator Verified! , Nike Air Max Torch 4 Size 9 M Women's Running Cross Training Shoes Silver/Orange , Merrell Womens Moab 2 Dusty Olive Hiking Shoes Size 7.5 (24966) , Skechers GoGa Mat Women Silver, Blue & White Walking Sneakers Size 8.5-M , Kim & Zozi Women's Rio Fashion Sneaker Tan Size 7.0 FeJS ,
"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."