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.New women's shoes ballet flat ballerina synthetic casual summer work blackNEW WOMEN CUTE CASUAL FLAT SHOES ~ Gray and BrownBorn Peggy Clogs Black Leather Pebbled Slip On Loafer 7M 38 c50303 1.75" heel , NIB Juicy Couture Beautiful Elegant Elastic Textured Ballet Flats Shoes w CharmEarth Kalso Loafer Women 6 B Charisma Black Leather Slip On Mocassin Moc Shoe , Womens Havaianas Slim Logo Metallic Holiday Lightweight Rubber Flip Flop US 6-11 , Born Womens SZ 8.5 M Brown Snake Cork Embossed Carri Flat D92106 NIB , SAS Free Time Beige Leather Oxfords Women's 9 WNew Munro American Kimi Black Leather Bit Slip On Loafer Women's Size 7 M* , EASY SPIRIT Gorgeous Leather KAFFI Sandals in Light Grey ~ size 40W ~ NWB $79 , Womens Reebok Gray/Pink Athletic Shoes 8.5 Worn Couple Times!NIKE ROSHE JUVENATE 5.5Y or WMNS 6.5-7 ORANGE PINK NICE USED see pics-details , Express Black Faux Leather Wedge Sneakers 10 Womens Fashion Shoes , NEW BALANCE 560V6 RUNNING Silver White Black Purple Womens Size 7B , Keds Sport Womens 6 US 3.5 EU Red Boat Gym Shoes Sneakers , Asics Gel Exalt Running Shoes, #T379N, Silver/Turq/Pink, Women's US Size 8ASICS Gel Contend 3 Womens Size 10 Silver Running Training Athletic Shoes F5-402 , Mizuno size 9.5M Wave Inspire 8 Osaka blue running womens ladies sneakers shoes , 1804 adidas BEACHCLOUD CLOUDFOAM THONG Women's Thong Sandals BB0505 , Nike Air Max Fury Pure Platinum/Metallic Red Bronze AA5740 005 Women's 8.5Women's Shoe PUMA ST Trainer Evo Sneakers 360963-07 Purple Cactus Flower *New* , Nike NEW Womens Air Max Tavas Running Shoes 916791 400 size 8 $90 , Nike Shox NZ 309206-061 Women's Size 9 Black Pink 2008 Running Sneakers , Mizuno Wave Emperor TR W Pink White Marathon Women Racing Shoes J1GB1686-01PUMA Women's Fierce Strap Flocking Wn Sparkling Cosmo-Sparkling Cosmo 8.5 M US , ASICS Tiger GEL-Lyte III Velvet Women's Peacoat/Peacoat N7T95858 size 8.5Vionic Elation Womens Purple & Pink Biomechanic Footbed Memory Foam Trainers NewShoes Skechers Mementos - Angel Face Memory Foam Snow Bootie 34341 NVY Woman NavNIKE SB STEFAN JANOSKI PREMIUM CNVS Womens 7 (5.5Y) Grey Aqua 654862 004 NEW , SAS Tripad Comfort Women's Size 6 M Brown Leather Tennis Shoes 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."