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.tibi new york pink & black fabric closed toe flats pumps Women's size 8 1/2 B , Mossimo supply co Brown/Maroon ballet flats size 8 , CLARKS LADIES PURPLE LEATHER FLATS-7M-BARELY WORN-NON-SLIP SOLE-VERY NICEWomens KEDS ORTHOLITE Navy Blue Slip On Rivets Comfort Shoes Size 8.5NOMAD Womens MAI TIA Red Multi Platform Espadrille US 7M (W8954-1)Lifestride Renata Slip-on Loafer Mushroom Microfiber MM1 Women's Size 9.5WEARTH ORIGINS Womens London Leather Closed Toe Ballet Flats, Dark Red, Size 8.5NWT Women's Skechers 48935/BLK Bikers-Cruisin Flats Black 9.5BX771 J. K. ACID shoes black paillettes women slip on , Aerosoles Women's Cosmetology Slip-on Loafer, Dark Red Nubuck, 6 M US , 02-2496 ASICS GEL-Cumulus 18 BR Running Sea/Indigo Blue/Blue Ribbon sz 5Merrell Barrado Sport Beige Zip front Shoes Fashion Sneakers Size US 8Women's Athletic Sneakers Outdoor Sports Running Breathable Sports Shoes 5 - 9 , Nike Free Run+ 3 Women's Shoes Size 9.5 Black Blue Pink Running 510643-064 , Sanita Women's Sandals Slides sz 6.5 Metallic Gold Shoes Dansko WF41 , Vans Women's Prison Issue 2 Tone Leather Double Velcro Sneakers Sz 10 NEW , **Puma- Tazon 6 FM Running Shoes, Women's Size 6.5, Black/Pink , Skechers Air Cooled Memory Foam Black Slip On Womens Shoes Size 7 NWOTS , JAMBU VEGAN TURQUOISE & PINK "SPIN" BALLET FLATS~~ WATER READY~ SZ 4M~~NEWWomen's Powerstep Men's Performance Compression Sleeves Quality First Athletic ShoesSkechers Ultra Flex Black Gold Women's Sneaker 12843/BKGDNike LunarMX+ Women's Athletic Shoes 415323-100 - Size 8.5Vans Old Skool San Francisco Giants MLB Women's 6.5 Skate Shoes New Black OrangeNew Reebok TOP DOWN SNAPS TXT Women Fashion Sneakers Sz. 8 - V55473 Pink , Bellini Women's Shadow Laser Cut SlingbackVANS New Sk8 Hi Slim Vault Lady size USA 7 , ASICS Women's GT-2000 4 Trail Running Shoe, Azalea/Melon/Perfect Plum, 6 M USSam Edelman Paulette Womens Blue Denim Leather Sneakers Shoes Size 7.5 M NewNIKE Women's Flex Trainer 6 Training Shoes Cool Grey/Turquoise SZ 7.5 831217 004Le Temps des Cerises basic 02- Blanc ,Tennis ,
"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."