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.Cute Demonia Shiny Pearlized Pink Glitter Leopard Ballet Flats Size 6, NEW , NATURALIZER GOSSIP Loafers Slides Shoes Sz 8 M Veggie Green WomensAutumn Run Women's Size 7 Mesa Tan Leather Upper Clog Loafers Shoes , Women's Apricot Orange Comfortable Flats Suede Size 5.5 (36 Euro) , AvaCostume Women's Chinese Embroidery Casual Mary Jane Travel Walking Shoes B...NATURALIZER Cecily, TAUPE.OX BROWN Slip-on Loafer Size 6M IN BOX , WOMEN SHOES NAOT MULES Size US 5M BLACK ISRAELCrocs Size 7 KADEE Black Slip On Ballet Flats Loafers New Womens ShoesTORY BURCH REVA Women's SLIP-ON PATENT LEATHER SIGNATURE BALLET FLATS Black 8M**Blue By Betsey Johnson Lucy Flats - Women's Size 8 - IvoryNEW Rockport V74173 Demisa Plain Moc Leather Loafers, Women's Size 8.5W, BlackAerosoles A2 Women's Love Spell Slip-On Loafer Brown Size 7.5 , Reebok DMX Ride Women's US 10 Gray Yellow Running Jogging Shoes Sneakers , Drew Shoes Rose Leather Ladies Womens 7 M 7M Copper Metalic Diabetic Shoes NIBLUIZA BARCELOS WOMEN'S AT141 BALLET FLATS VERNIZ FIRENZE MARINHO US SZ 10 MEDIUM , Heavenly Soles Women's Wide E Fit Ballerina Shoes TW4 Grey Size UK:8E US:10E , Adidas Adizero Women's Sneakers Size 6.5 Teal Black Gray Silver Tennis ShoesSkechers Women's Shoes Size 9 Shape-Ups Walking Shoes Grey PinkKEEN Presidio 5322 Brown Nubuck Leather Hiking Walking Shoes Women’s US Size 8.5 , Nike Air Max Run II Women's Size 7.5 Running Shoes - Very Nice - Fast Shipping , Skechers Womens - Pink Running Shoes Size 9 (351888) , Asics Gel Venture 5 Women’s Navy Blue Pink Running Trail Shoes Size 7.5 T5N8NConverse Chuck Taylor All Star Low OX Grey White Women Casual Shoes 560644CNike Air Zoom Fit Agility 2 Womens Training Shoes Orange/Sunset 806472 800 (S,2)NIKE Air Zoom Strong Womens Sz 8 Shoes Gray Black 843975 100Demonia Women's Scene 20 Mary JaneEUC NIKE FLYKNIT LUNAR 3 RUNNING SHOE WMNS US 10 698182 001 BLACK WHITE OREO A5HOGAN Women's Black & Gold Leather Suede Branded High Tops Sneakers sz 36 Italy , New Balance Women's WL515 Athletic Running Shoes Grey/Blue/Green , New NIKE Women's Zoom Rival Track Running Spikes Cleats Sizes 6, 11, 11.5
"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."