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.Weejuns Bass Brown Mules Flats Shoes Slides 6 MTrotters Womens Haley Black Leather Woven Moc Toe Slip On Flats Size 9.5S NWOB , Anne Klein Iflex Purple Suede Loafers Flats Buckle Accent Size 6 MChinese Laundry Womens EASY DOES IT Suede Pointed Toe Ballet, Blue, Size 7.5 DEKAerosoles Women's Shoes Black Brown Animal Fur Leather Loafer .75" Heel Size 7MSAS Tri-Pad Comfort Food Bed Shoes Womens 10 Loafers Black Moccasins HorsebitDana Buchman Red Wedge Heel Ribbon Bow Size 10M Never WornAnne Klein Women's Petrica Navy Leather Ballerina Flat , ZARA Flat Tubular Sandals Size7.5 (38) , Salvatore Ferragamo Beige White Leather Link Detail Loafers Flats Size 8.5AA , Sperry Top-Sider Women's Ivyfish Boat Shoe (STS94107) SZ 5.5Women's Sperry Topsiders Firefish Ripstop Black Canvas STS97717 Boat Deck ShoesWomen's New Balance 1340 v2 running shoes sneakers size 8.5 , New Balance SD130RG D Pink Men Sprots Sandal Slides Slippers SD130RGD , New Balance 505 XC Cross Country Rock Stop Sneaker Shoe Gray Green Size 10Bare Traps Womens Kessie Fabric Low Top Slip On Fashion Sneakers , Women's Skechers BOBS Luxe Sparkle Dot Ballet Flat 31460 LTGY Light Gray NEWMIZUNO Wave Rider 17 Women's running athletic shoes Neon Green & Pink Size 8 MMERRELL WOMENS BAREFOOT RUNNING SHOES 99% TREAD SIZE-9.5 , womens nike flex supreme tr 5Skechers GO STEP Ballet Slip-On Shoes - Luxe 7.5 MEDIUM BLACK PO$39.99 Puma Women Leadcat Satin black 365338-01Women's Nike Rosherun Womens Shoes For Sale Athletic ShoesCole Haan ZEROGRAND Perforated Leather Trainers, Women's Size 6.5 B, BlackWOMEN'S SHOES SNEAKERS REEBOK YOURFLEX TRAINETTE [CN4730] , Vans Wmns Sk8 Hi 38 Reissue Dx High Top Whisper Pink Leather VN0A38GJOESNIKE AIR PEWTER AND BURGANDY SIZE 11Puma Suede Jelly Shoes, Grey Leather, 365859 02 Women’s Size 9.5Brooks Adrenaline GTS 16 Blue Tint/Pink Glo/Peacoat Road-Running Shoes 6M , Converse All Star Size 12 Women’s BLACK Sequin Low Top 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."