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.WALKING CRADLES Womens FAWN Black Microfiber Ballet Flat US Size 9.5 M , RAMPAGE BLACK "POLKA" FLATS - CUTE WOMEN'S SHOES - NWOB - FUN FLATS! , Meat Bun White Flat Ballet Shoes with Bow Sz. 38 (7,5) , Lands End Women's Wedge Sandal Size 7BShoes Low Hill Black New Fabric Very Comfy Size 6/5 , New Woman Ballet Flats Ankle Strap Ballerina Slip On Shoes , Women's Josef Seibel Size 37/6-6.5 Loafers Shoes Brown Leather Air Massage Y9 , Dansko Womens Black Leather Loafers/ Mules Size 37/6.5 M , Callisto Women's Sorcha Ballet Flat, Grey Suede, Size 5.0 , Natural soul by Naturalizer Vivian latte Smooth 9M $99 Retail,On Sale Now!!! , Ladies Clarks Cloud Steppers Mule Shoes Sillian FreeDr. Doc Martens 11306 Brown Leather Bicycle Toe Casual Chunky Oxford Womens US 7 , Brand New Custom Made Vans Seahawk Colors, Blue, Green and Grey 7.5OluKai Hi'ona Sandal Womens 7 US 37 EUR Leather Tan Comfort 20286 Buckle , MIZUNO Wave Inspire 10 "Mondrian" White Red Running Shoes Womens Sz 11.5 M , TRETORN NYLITE WOMEN'S TEAL GEOMETRIC SNEAKERS-NWOB-NEW -" SEKSTI SOLAR INDIAN"SKETCHERS SHAPE-UPS 12320 WOMENS WALKING SHOE SIZE 8 WHITE Blue Gray White , ADIDAS Daroga Hiking Sneakers Women’s Size 6 Adventure Trail Running Shoes - JC , Nike Womens Free Run Pink Mesh Running Shoes Run Sz 5y Gym Athletic TennisRyka Dynamic Cool Mist Cross Trainers Athletic Shoes Womens Size US 7 Eur 37.5 , NEW Adidas Superstar Glossy Toe Womens Style : S76723 Blue Womens Size 8 , Women's Saucony Excursion TR10 Running Shoes Size 8.5 Excellent!Bernie Mev Women's Mid Olympia Fashion Sneaker, Black, 37 EU/6.5-7 M USMerrell Womens J09546 Boulder/Brown Hiking Shoes Size 7.5 (15567)Men's Shoes Slippers FuckThePopulation FTP House Slippers A Great Variety Of Goods SlippersVans Iso 1.5 Mesh Ultracush Pewter Ballerina Shoes Size Men 8.5 Women 10Skechers Women's Go Run 600-15082 Sneaker,Vans Classic Slip On Suede Fleece Black Women's 8.5 Men's 7 Skate Shoes New , Reebok Women's AstroRide Walking Shoes GG8 Whisper Teal/Alloy Size 8.5 , Adidas ClimaCool CC Fresh Bounce Womens Running Shoes Fitness Trainers Peach
"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."