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.Leather Loafers Flats Shoes Heather Brown Womens Earth Spirit Gelron 2000 Sz 9.5 , Smet Womens French Ballet Studded Flat Shoes, Black, US 5Dansko Carol Silver Metallic Pewter Moc Driving Shoe Soft Comfy Wedge 38 8Vintage Dexter USA Womens Size 6 & 1/2 Brown Leather Keltie Tassel Loafer ShoesMID WEST GREEN SHOES WOMENS SIZE 6ZEETA BLACK/BROWN LEATHER CLOGS WOMENS SIZE 6.5-7 mislabeled size Y399Lauren Ralph Lauren wmns sz 6 1/2 B Pink White Tassel loafer EUC Made in BrazilEcco Women's Black Leather Mary Jane Shoes Size 36 /6 US , New Directions Womens Bella Closed Toe Slide Flats, Gold, Size 9.0 , COMFORTVIEW Red / Black JUDY Mules Slides Block HEELS Size 7.5 M Women's NIB NEW , Salvatore Ferragamo Women's Brown Leather Loafers Shoes Size 7 1/2 A SN 9931Dansko 41 Mary Jane sandal camelNicole Black Heart patent slip on smoking shoe tassels w/rhinestone 9MBandolino Womens Yara Pointed Toe Slide Flats Black Synthetic Size 6.5 3FAi , ECCO Women's Vibration II Toggle Sneaker Leather Mesh Black Slip-On Size 40 EUNew Nike Air Force 1 ‘07 SE Women’s Size 7.5 MUSHROOM/MUSHROOM AA0287 200 , NIKE Womens Nike Ultra Comfort Slide 882695-100 WHITE/BLACK-WHITE Womens Size 7 , Women's Reebok Freestyle Hi - Pink - Width: med - Fashion SneakersNew $100 Women's PUMA Suede Platforms Sneakers Shoes Black & White Size 9.5Adidas Originals Vigor 4 TR Womens Cross Training Shoe D74004 Sz 9.5 US NWOT , MERRELL LEATHER SHOE, WOMEN'S SIZE 7 EUCConverse Womens Size 8 Chuck Taylor All Star Gemma Knit Oreo Shoes SneakersNIKE DUNK LOW WHITE GLACIER CASUAL WOMENS WMNS SZ 7-10 302517-112 , Girls' Nike FS Lite Run Running Shoes Black/Metallic Silver/Hyper Pink Sz. Us 7Y , Merrell Moab Dusty Olive Women's Hiking Shoe 9.5MSkechers Performance Women's Go Flex-Ability Athletic Sneakers Shoes Charcoal , ASICS Womens - Aquarium/Sun/IndigoBlue Running Shoes Size 7 (367985) , New Saucony Womens Spitfire Teal/Blue Running Shoes Size 9.5 , NWB FILA SOAR 2 Running/Cross Training Shoes Sz 11 ~~~FREE SHIPPING~~~ , Cintura Guess Donna Bianco Belt Woman White Art1531 M ,
"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."