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.OTZ Course Linen Unisex Slip On Shoes - Mens 5 Womens 8 - Chartreuse - 300GMSTalbots Shoe Size 6M Womens Black leather Patent Leather Pointy Toe Shoes FlatsChinese Laundry Womens cinamon Fabric Closed Toe Loafers Black Lycra Size 10.0 , Sperry Topsider Womens Angelfish Boat Shoe Womens Size 7 9102047 Leather EUC , Dr. Scholl's Idol Mule Slip On - Women's Size 7.5M BlackLifeStride Womens vanity Square Toe Loafers Tan Size 9.5 y3jKSperry Topsider Seacoast - Blue Canvas - Size US Womens 8 , Extinct by Miz Mooz Women's Diara Flat, Red, 38 EU/7.5 M USNWT Women's Size 6 Op Art PURPLE Flower Power LL Bean Clogs Size , Skechers Womens moda Closed Toe MulesFashion Women Hidden Wedge Heel Pull On Shoes Sneakers Athletic Casual LoafersGirls Womens Round Toe Sequins Mesh Hidden Heels Breathable Casual Sneakers G , Puma G. Villas Pink/white Casual Atheltic Shoe Womens Size 9.5 , Women's Brooks Addiction Walker shoes sneakers size 9 AA , Asics Gel-Cumulus 20 Women size 7.5 Running Shoes , Women's Ellie Women's Nora Stylish Athletic Shoes , EUC WOMENS ADIDAS ULTRA BOOST ST US 8.5 RUNNING SNEAKERS BA7832 A6NEW Nike Womens Zoom Elite+ 6 Running Shoes Blue Gray Size 10.5 , NEW BALANCE WOMEN 580 SEASIDE HIDEAWAY SZ 12 BLUE LIGHT BLUE WRT580RB , VINCE Sneakers Suede Leather Black Platform Slip on Women Size 7Nike Free RN Flyknit Fire Pink/ Purple/Orange Running Shoes Size 6.5Y youth/kidWalking Cradles Women's Buckley Slip On , New Balance WT1210BK - Women's Trail Running Leadville Ultra-Runner Shoes size 6Skechers Women's Microburst Topnotch Walking Slip-OnVans Authentic Canvas Dress Blue Nautical Blue Women Men Sneakers VN-0NJVLLARARE Women's Shoes Adidas Samba Size 5 All BlackMBT Womens Swiss Chapa w Azul Walking Running Rocker Toning Shoes 7.5 , ASICS Gel Tactics Women’s Athletic Sneakers New! , Michelle K Sports Womens 8 Med Walking Shoes Suede Leather Sneakers Beige Floral , Cole Haan Women's Size 8.5 B Beige Green Casual Suede Shoes D19965 Arch Support ,
"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."