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 Unstructured Black Leather Mary Jane Stitched Ballet Flats Size 8.5 , New Women Qupid State-07 Faux Suede Ankle Strap Tasseled Ballet Flat , American Eagle Outfitters SHOES WOMENS SIZE 6 , Onitsuka Tiger Women's Kanoka Tan Flats 7M , � Cloudwalkers Penny Loafers size 9.5 W Brown Suede; Patent Leatherette AccentsNew without Box Orthofeet Springfield Spandex Black Mary Janes Size 5.5B , Women's Sam Edelman MILES Black Shimmer Loafers Shoes Size 10 MDoc Dr. Martens Oxfords (PK07D) 90's Grunge Women's Size 5 Brown , SPERRY WOMENS CREST VIBE CREPE CHAMBRAY SALMON SIZE 9.5Dansko SANITA Oil Rubbed Black Mule Clog Sz 41 10.5 , ART Ballerines Tissu Imprimé Vert Foncé T 38 TBEEasy Street Womens Barbara Low Top Slip On Fashion Beige Floral Size 7.0 vQSFCreative Recreation W Cesario XVI Black Velvet shoes sz 7 , NEW Lucky Shoes Kool Shoes. Size 6 U.S. euro 37Dockers Court Shoes Slippers Low Shoes Slippers Grey NEW , CONVERSE Ladies Purple/Lavender Low Top Sneakers Size 10US 41.5 EU , Womens Asics Gel Cadence 2 Running T16CQ Training shoes size 6Nike Air Max Premier Run Running Shoes White Light Aqua Womens Sz 7.5 - 789574Converse One Star Green Suede with Orange Trim Womens Size 7Womens Converse Chuck Taylor All Star Lo Black Sequin Sneaker Trainer Size 12 , Adidas ADI Ballerina W Men's Shoes Size 7Nike 6.0 Dunk High Womens Sz 8 Black Blue 342257-002Puma Suede Classic Gold Red - Womens - Size 9.5 BGEOX Leather Block Heel Ankle Boots - Annya Mid BLACK 6m**Saucony Freedom ISO Running Shoes Womens Size 9 BlackNew Women's Adidas Stan Smith Pink Trainers Shoes Sz.7.5 EU.39New Balance WW840v2 Sneaker - Women's Size 7(2E) Black , NEW NIB ADIDAS? ADIDAS THRASHER TR W PREMIUM ATHLETIC RUNNING/COURSE , Women’s Nearly New KEEN Trail Shoes Size 6.5 US Brown Leather Flawless , EUC Nike Fre 5.0 TR Fit 4 Women's Size US 7.5 Black Pink 629496 011 A2 ,
"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."