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.Women's Rockport Brown Leather Loafers US 7.5 N Sz Clean!! Great condition! , ZARA FLORAL PRINT BALLERINA FLAT SHOES , SIZE 39Faded Glory SHOES WOMENS SIZE 6 1/2 , Single 1 Right Shoe Size 7 Black Mary Jane Style New Comforts by Madness , Spot On F8782 Ladies Tan Snake Effect Pu Flat Shoe (32B)jessica simpson flat suede shies size 8,5 practically new taupe , SAS 'Siesta' Mocha Leather Moc Toe Oxford Comfort Walking Shoes Women's Sz. 8NBorn Women's 6.5 M Black Quilted Patent Leather Ballet Flats Round Cap Toe GUC , CLARKS Wave Women's Black Leather Comfort Slip On Shoes 33155 Sneakers Size 8.5M , Natural Comfort Ellen Womens Leather Comfort Shoes , Contours by Isotoner Women's Brown Oiled Leather Mule ShoesWOMEN SHOES SAS MULES Size 11S BROWN LEATHER USVionic Splendid Midi Loafer Womens 6.5 M Natural Snake Gray Black Shoes $130 , Prada Womens Loafers Size 39 9 Black Suede Silver Tone Hardware Block HeelMelissa Women's 'Cosmic AD - Blue/White SandalNIB Ecco Incise Enchant Ballerina Slip-on Muted Clay Leather Flat Shoes Size 10MSoft Spots Bonnie Wine Leather Loafers Shoes Size 8W , Tommy Bahama Enisa Canvas Slip On Shoes, Women's - Size 6, NavyRinaldi Designs D’orsay Ballet flat Bronze Floral Lurex embroidery with crystalsBROOKS GHOST 6 WOMEN'S ATHLETIC RUNNING SHOE Sz 11 BABY BLUE GRAY 1201381D620Propet Women's Discover SlideNEW! Women's Skechers Memory Foam Comfort Sneaker - Size: 8.5 , Propét W3902 Diabetic Sneaker Womens Size 6 D, Sport White , NIKE Womens Nike Zoom Strike AJ0188-016 GOLD/WOLF GREY Womens Size 11 Brand New , NEW Women's Puma FAAS Lite Spikeless Golf Shoes ECO OrthoLite Black/Pink Size 10 , Factory direct wholesale Onemix New Women's Lifestyle Running Shoes SneakersADIDAS CLOUDFOAM GALAXY 4W WOMEN'S WHITE TRAINING SHOES S80642Guess Alexea Casual Platform Fashion Sneakers 948, Gold Multi, 8.5 US , Vans Sk8-Hi Slim (Navy/True White) Women's ShoesVANS Authentic Heron/True White Purple Skate Casual WOMEN'S 5.5 ,
"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."