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.Dansko Professional Women's Animal Print Leather Clogs Loafer /US 6.5-7 , Rockport Off White Womens Loafer 9mBASS WOMENS RED LEATHER LOW BACK LOAFERS 2" HEELS SIZE 7M , SAS Womens Pinch Leather Loafer 10 M Tripad Comfort Brown Moc Toe Kilt TasselWOMENS CROCS Melbourne 2 Flat Vamp Loafer Shoe size 910 Pink Beaded Silk Flats Handmade Bollywood Belly Dance Indian Khussa Sari ShoeCIRCUS BY SAM EDELMAN WOMEN'S BLACK SHOES LEATHER SIZE US 7 M , VIONIC 'Spark Minna' Ladies Grey Snake Leather Ballet Flats Sz. 8 WIDE NIB , Mephisto Women's Pewter Leather Cool-Air Slip On Horse Bit Loafer Size 6M , Natural Soul Womens Wilson Leather Closed Toe Loafers Black suede Size 7.0 0tK , Stuart Weitzman NEW Womens Loafers Shoes Brown Casual 6 , Womens Sandals Flats Heel Hollow Out Slip On Casual Brogue Pointy Toe Shoes New , Womens Saucony Raptor Gray Running Shoes Size 7M (E381) , New Balance SD750PP D Pink White Men Women One Click Sandal Shoes SD750PPDMerrell women's vibran ventilator gray suede leather hiking trail shoes size 7.5ASICS Yellow White H900N Canvas Sneakers 39.5 6.5 - AG5Womens Sequins Flat Heels Running Shoes Retro 9W Stars Sneakers Casual Athletic , Women's womens vans sneakers New Varieties Are Introduced One After Another Athletic Shoes , Women's merrel 7.5 women Wear-resisting FlatsPuma Eskiva Mid Remaster Puma Black 361628 03 Women's SZ 7Women Casual Shoes 2016 New Fashion Women Shoes Mesh Shoes Woman With Breathable , Puma Disc Wedge Coastal Womens White Blue Green Trainers 358050 02 U4 , Puma Suede Stripe Black Zebra 36024901 Leather Classic Casual Women , Skechers Women's D'Lites Play On Training Shoe , PUMA 364587-02 : Women's Basket NS Wn Platform Icelandic Blue Sneakers , New Balance XCR700 V4 Women’s Running Shoes Pink/Black Size 5.5 B , adidas energy bounce w - Grey - WomensVans Authentic Slim Perf Stars Black Sz Womens 9.5 NIBSperry Top Sider Womens Shoes Size 8.5 Charcoal Gray Wool Flat Slip On Sneakers , New Balance Women's Walking 577 Shoes White Factory Second ,
"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."