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.Handmade Women's Traditional Velvet Shoe Casual Ethnic US 7 8 9 10 11 Sizes , SAS *SIMPLIFY* GOLD LEATHER PLAIN FLAT LOAFERS - LADIES 10SLC Lauren Conrad Sky Blue Floral Flats. Size 8. , Hollow-Out Pointed Toe Flats Size 7 Size 38 Custom Made To Order LoaferTheme Green Slip On Flats Shoes (Womens US 6.5) STOCK #: 271268Earth Origins by Earth 7 Brown Leather Slip On Women's ShoesSoft Style Womens Pran Closed Toe Loafers Black Size 9.0J. Crew Red Loafers - Size 5.5 (US) , DR DOC MARTENS BLACK LEATHER women's flower ankle shoes 12283 Size 7 USKlogs Missy Women's Clog Shoes Display Model Henna Patent 8 MWomens Sz 10B EARTH "Ginseng Bronze" Brown Metallic Leather Shoes , BCBG Daz-BA Pumps Black Leather Size 8.5 / 39 High Heel Ankle Strap , dune london shoes with leopard skin design. It is new. Size UK6/US8. Ship ASAP.NEW BALANCE GENTLY USED WALKING STRIDE PATH WHITE SHOES SIZE 6.5M EURO 37 , NWT CHARLOTTE RUSSE Star Print Low-Top Canvas Sneakers Faded Blue Americana Shoe , Dansko Black Leather Clogs Size 37 , Puma Women's Sz 9 Athletic Shoe Speed Cat - Gray Suede Running SneakerNIKE Women's In-Season TR 6 Cross Training Shoe, US 9.5 / WhiteNike Zoom Trainer Essential Women's Running Shoe Blue/ Green/ White Size 9(US) , Missoni Converse Ox Low Top Electric Paint Splatter Sneaker Women's Size 6 MNike Free RN GS Run White Black Kid Youth Women Running Shoes Sneaker 833989-100Nautica Norwich Womens Flat- Choose SZ/Color.NIKE AIR ZOOM HYPERACE WOMEN'S VOLLEYBALL SHOES SIZE 6.5 WHITE/RED 902367-106DAWGS Women's Ultralite Golf Walking Shoe White/Black 7 M USSKECHERS D'lites Women Sport Casual Comfort Memory Foam Sneakers NEW SZ 7.5 , ASICS T3N5Q Gel Storm Running Racing Training Shoes Sneakers Pink Womens 9 , Nike Air Zoom Fearless Flyknit. Brand new. Women sizes: 6.5 & 8.5Merrell Vibram Algiers Pilot Purple Performance Exercise Sport Shoes Sneakers 9 , Skechers Women's On the GO 600 Preferred Thong Sandal TaupeJ Slides Women's Proper Sneaker White Size 7.0
"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."