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.WM White Mountain 'Gracy' Ballet Flats Black Synthetic Leather Size 9M , Natural Soul by Naturalizer Brown Shoes 8 M Leather Slip On Loafers Womens , PINK & PEPPER Womens QUEENIE Black Multi Clogs Size US 8M (8888448-447713) , Disney Women's Alice in Wonderland Oxford Shoes USA Women's Size 11 Canvas Flats$89 Sperry Angelfish One Eye Boat Women's US 7 in Linen/Oat LeatherBELINDA Blink Synthetic Bow Slip On Casual Women Flats Office Shoes Silver 7.5 , Arcopedico Elio Parodi Beige/Ivory Knit Slip On Wedge Heel Mules-EURO 36-US 6-7 , Women's Born Forsythia Ballet Flats Shoes Size 8.5M US/40 EU Gold Leather AD1 , Doc Martens Double Strap Mary Janes Leather Womens 9Jambu Womens Bali Casual Slip On Clog Mule Shoes Black Size 8 M , Fortress of Inca - Ladies Flats 7 Blue Aztec Embroidered Pattern NEW NIB *uniqueWomen's Shoes Lacoste Marice BL 2 SPW CNV Slip On 7-32SPW0142024 Black *New*Clarks Raisie Eletta Black Tweed Loafers Size 8.5M D749/J. Crew Womens Jacquard Stacked Heel Loafers Shoes Size 5 E1345Skechers BOBS Womens Bobs Clique Sneaker- Select SZ/Color.Prada Sport Gold Tone Metallic Leather Silver Tone Hardware Loafers Size 38 8 , samples shoes BALLERINE ETNIES PLUS FLING BLUE WOMENAsics? GEL-EXALT 2 Run Shoes Everyday Women Size 10 pre owned , Nike Air Gray Purple Peach Running Shoes Sneakers Women's Size 8 , Good Cond Pony MX77 Low Sneakers White Leather With Blue Suede Sz 7.5 , Womens Mary Jane Strap Walking Cut Out Sport Lightweight TrainersWomens Pearl Flowers Sneakers Pu leather Flats Fashion Oxfords Boots Casual Slip , New Balance Minimus Vibram Women's Running Shoes WT20BG2 Sz 8.5 US , Converse Women 8 Junior 6 Chuck Taylor All Star Gray Purple HighTop Shoe Sneaker , Women's RENÉ MANCINI 36.5 NOIR Carmel, Delicate Flats , Reebok Classic Leather Women's Eucalyptus/White CM9161Saucony Womens Pink White Gray Running Shoes Sneakers USA Size 11 EURO 43 , **Saucony Freedom ISO Running Shoes Womens Size 9 BlackCONVERSE One Star.. Suede.."Run Like Hell" Shoes...Size WO's 10.5 Mens 9Vivobarefoot Womens Ultra II Water Shoes, Black/Red, 35 EU / 5.5 US ,
"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."