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.AR35 Cellia Ballet Flats, Black/Cognac, 8 USMerrell Jungle Moc Wrap Sandstone shoes size 9.5Madewell women shoes brown size 8.5 , Alegria MERI Water Resistant Ankle Boots Faux Fur Meri. SHINY FLORAL W-EUCTraditional Handmade Slippers Flip-Flops Indian Women Shoes Clogs Flat US 6-10Ann Taylor LOFT Brown Canvas Flats Ankle Strap Casual Fashion Shoes Women Sz 7MTALBOTS Size 7 1/2 Brown Ballet Flats Shoes w/ Brass tone Medallion 7.5CIRCUS BY SAM EDELMAN WOMEN'S BLACK SHOES LEATHER SIZE US 7 MBOC Born Margaret Women's Brown Leather Slip On Clogs MW Size 8.5US BC6433 , Toni Pons Shoes 599155 Beige 37Pleaser Creeper Side Cutout Buckle Women Flats Slv Hologram-Blk Vegan LeatherMocassins Sioux Cuir Vernis Orange 38 ½ , Clarks Navy Blue Perforated Leather Everlay Dairyn Slip on Comfort Shoe 10 NEWWomen's New Balance Running 790 Shoes Size 7 1/2Dexter Ladies White Leather Sneakers Size 8 Performance Shoes Bowling Walking , MISMATCHED NEW Women's KEDS ARIA BLUE/RED Casual LEFT SZ 8 RIGHT SZ 7.5 Shoes , Jessica Simpson Womens Lynsey Ballet Flat- Select SZ/Color. , WOMENS NIKE AIR MAX DYNASTY RUNNING SHOES SZ 6.5 37.5 B USED SNEAKERS 816748 002 , Classic Polo Rugby Billiard Green Velvet Slippers w/ Bullion Griffin Sz: 12Skechers Women’s D'Lites Grey Aqua Leather Athletic Sneaker Shoe Size US 10 , Nike FS LITE Run 3 Running Training Womens Shoes Size 10 Black /BlackCalvin Klein Womens Juno Black Fashion Sneakers Shoes 8 Medium (B,M) BHFO 5257 , Women's Skechers Sport Women's Dynamight-Breakthrough Sneaker Elegant Shape Athletic ShoesWomen's CAPPELLETTI WOMENS Slid on 9 Surprise Athletic Shoes , NIKE NWOT White Brown Green GOLD Checkered Pattern 306499-271 Women's SIZE 7.5 , Nike T-Lite Xl Women's Athletic Shoe 616696 101 Size 11Ana Lublin ESTELA_ROSA sneaker Women's - colour Pink USNEW NIKE WOMEN'S FREE TR6 TURQUOISE TRAINERS TRAINING SHOES 833413 300 SIZE 11New Adidas "ADIZERO XT BOOST" Women's Running Shoes Size 7 Blue/Pink S74412NEW! Under Armour 1266243-914 Womens Micro G Speed Swift Aqua/White 8.5M 101P aa
"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."