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.Womens CLARKS PRIVO Size 6.5 M Brown Suede Comfort Sport Walking Slip On Shoes , Womens Clarks Collection Loafers Leather Slip On Shoe Black Size 7 MediumShayna Mary Jane Crocs Hot Pink--Size 7Joey O Womens Shoes Sz 8 M US Orange Green Flats Slipons Dress Casual Loafers , Hotter Aura Mary Jane Comfort Shoes US 11 Light Gray NEWNEW Naturalizer Natural Soul Fanna Loafers Black Patent Croc 7M , Sperry Top-Sider Songfish Boat Shoes 787, Snake Oat, 6 US / 36 EU , Merrell Windsor Wine Expresso Hiking Casual Shoes Women's Size US 7/alegria mules #agl-602 euro 41 us 10 color brown , MANOLO BLAHNIK Pony Leopard Design Ladies Shoes Flats SZ 40 1/2 US SZ 10 , Mephisto Air-Jet Womens 8 US 5.5EU Black Suede Wingtip Oxford Tie Shoes FranceNew Balance sz 8.5B 7500 black pink running womens ladies tennis sneakers shoesAsics Gel Exalt Running Shoes, #T379N, White/Turq/Silver, Women's US Size 9 , BEJEWELED SLIP-ON LOAFER WOMEN GOTA-1-05 ELEGANT BLACKWomens Cliffs by White Mountain NIB Highlife Brown Flats 6 M , **Steven by Steve Madden Traveler Sneaker - Women's Size 7, BlushASICS GEL-SUSTAIN TR 2 Purple Hot Pink Womens Size 9.5 , Men's Wool Fleece Memory Foam Slippers Slip On Clog House Shoes 11-12 GrayADIDAS ORIGINALS WOMEN'S CC OSCILLATION GREY YELLOW RED SHOES SIZE US 7.5 G49946Women's Funtasma Women's Gogo Beautiful In Colour Athletic Shoes , adidas Originals Womens Gazelle Casual Shoe Brown/White/Gold Mt BY9360 , Converse Chuck Taylor All Star Syde Street Mid Black Womens Canvas Trainers , Nike Air Force One 1 Tennis Shoe Size 5.5 Black Athletic Trainers Low Top LeatheNike Rival S Sprint Track and Field Spikes Womens Size 9.5 Blue Green 806558403adidas Women's Cloudfoam Daily QT Clean Court Shoe , Nike Air Max 1 X QS Maria Sharapova 633737 002 SPNY Nike Lab Patta Parra SZ 6 , Superga 2750 Cotu Classic Black, off white trim. 11 Women’s, Men’s 9.5 , Saucony Grid Cohesion 15181-16 Grey White Pink Sneakers Shoes size 8.5 EUCNike Golf womens air go shoes 309920 441 trainers sneakers shoes Size 7.5 #S232Propet W5104 Womens Travel Active Lightweight Slip On Fashion Sneaker Shoes
"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."