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.Pirouette By Jane Winkworth Silver Metallic Bow Ballet Flat Shoe 40 10Natural soul by naturalizer women white leather upper flat sneakers shoes size , Liz Claiborne SHOES WOMENS SIZE 8 MNATURALIZER NATALIA Front Zip Slip On Leather Loafers Black Womens Size 11M ZQNaturalizer Natural Soul Size 7.5 W Brown Leather Slipon Sandal Pre-ownedMinnetonka Moccasins Brown Suede Fringe Driving Mocc Slip On Shoe Women's sz 8.5 , BC Footwear Women's Petite V-Suede Ballet FlatBare Traps Womens Indiana Closed Toe Slide Flats Yellow Size 8.0KEEN Erin MJ US 9.5 Suns Orange Suede & Mesh Flats Shoes NEW , Jack Rogers Women's Tucker Casual Slip-on Sneaker / Ropy Espadrille Trim , Cole Haan suede leather slip on clogs mules, green, 8B**Skechers Women's Bikers Roamer Slip On Shoes - Size 8, Black , Clarks Collection Size 7 M ESHA MARIGOLD Black Leather Loafers New Womens ShoesNew Sam Edelman Women's Freya Leather BalletBordello Women's Tempt 10Ivanka Trump Womens Euma Dress Square Toe Low Heel D'Orsay Shoes BHFO 0713 , Light breathable womens sneakers with ergonomic sole slip on elastic knit HOTOnitsuka Tiger Womens Fitness Sneakers Platinum / Brown US 8Eileen Fisher Womens Sneakers Size 6.5 Brown Gray Round Toe Hi Top SuedeJARLIF Women's Platforms Fitness Slip On Canvas Athletic Walking Shoes US 7.5-8Women Skechers Go Step Lite INDULGE Performance Shoes Size 7 WIDE new in boxWomen's Trotters Women's Sarina Ballet Flat Superior Quality FlatsNike Flex Trainer 7 Fade Womens Training Shoes Blue Black 898480-400 SIZE 7 - 10KURU Womens Quantum Gray/Purple Plantar Fasciitis Running Athletic Shoes Size 8 , Women's Skechers Ultra Flex Weave Away - Black - Width: med - Cross TrainingPuma Eskiva Mid Cross-Trainer Sneakers 892, Silver Metallic, 9 US / 40 EUPhilippe Model Black High Top Suede and Leather Women's Sneaker 38 -7 1/2SKECHERS Women's og 98 GARDEN PARTY NAVY FASHION SNEAKERS DESIGN IN LA SZ 8 , Nike FS Lite Run 2 Womens Running Training Shoes Size 9.5 Gray Turquoise , Nike Sweet Classic Textile Shoes Size 6 Rare Hard To Find Women’s Sneakers ,
"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."