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.Clarks Everyday Active Air Womens Blue 6 1/2M Pumps 85268 Leather ShoesLadies SKECHERS Black Mary Jane Walking Shoes Size 8.5Partners Joan Womens Brown Leather Casual Loafer Shoe - Size 10METIENNE AIGNER Womens 5.5 M brown leather ivory linen ballet flats shoes slip-onSAS Womens Tripad Comfort Shoes Size 7M Moc Toe Tassel Loafers Brown-3836 , Eastland 10 m slip on womens shoesCoolers Summer Friuts Shoes FREE POST BRAND NEWLADIES BOBS BY SKECHERS SLIP ON SHOES 34218 / NVW PATRIOTIC! RED, WHITE BLUEWomen's Puma Flats size 9 1/2 , Vince Camuto Black Perforated Suede Loafers - Size 7.5Women's Bare Traps "Rowen" Shoes/Flats Pewter in color WR11111 LadiesKeen Women's size 38 7.5 Pink Canvas Slip on Boat Loafer Sneaker Shoes Elastic , Boden Women's Suede/Nubuck Brogues Navy & Pink | / US 9.5/10 , Rieker Women's Slip-ons with soft leather insole, brown, Real leather NEWHotter Women's Abbeyville Casual Slip-on Tassel Loafer Shoes MM1 Size 7.5 MBROOKS PURE GRIT WOMENS 9.5 PURPLE BLUE BLaK NICE USED V-CLEAN see pics-detailsRockport Women's Adelyn Ballet Flat, Black Amp Lux, 5 M USSperry Top-Sider Intrepid Womens MD Grey/Dark Gr Boat Shoes STS96368 5.5 MNew Balance 926 Black Athletic Walking Shoes Women's Size 9B WW926BKAdidas Gazelle Sneakers Women Gray White Size 7.5NIKE Womens Free RN Running Shoes White/Black Size 8 Training SneakersUS Cali Women LED Light Up Air Cushioned Sneakers Running Athletic Tennis Shoes , Puma Womens Cell Riaze Black Heathered Athletic Shoes 10 Medium (B,M) BHFO 6669Puma Women's SUEDE PLATFORM CRUSHED GEM Shoes Marshmallow/Gold 365866-02 b , ASICS GEL FUJI Trabuco 3 Neutral Womens 10 42 EUR Charcoal Ruby Red T4E9N Trail , Skechers Goga Mat Go Step Women’s Gray Velvety Walking Shoes Sz 9.5 /CHARNWB Gray K SWISS K*SWISS Shoes W/Memory Foam Sz 6M $75 ***FREESHIPPING*** , Pre Owned New Balance Women's WX608V3 Cross-Training Shoe. 6.5 M. White, pink.US7/37.5 Alexander McQueen By Puma Women's McQ Move Mid Leather Athletic boots , NIKE Womens Solay Thong Print 882696-602 ARCTIC PINK/WHITE Womens Size 7 ,
"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."