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.Peace Moccasins EMILY Women's Light Grey Suede Moccasin Fringe Loafers Sz US 9.5Brown Kim Rogers Leather Slide Shoes Size 9M Clog Heel 2 Inches , US Size 5 Women Indian Handmade Blue Velvet Shoes Mojari Jutti Flip Flops Flats , CLARKS Haydn Harvest Wo's 8M Brown Leather Lizard Print Loafer Slip OnComfortable Womens Summer Flats Shoes Driving Loafers Slip on Pumps Stars SandalNINE WEST WOMENS BROWN WOOL & LEATHER LOAFERS SHOES SIZE 7 M USLucky Brand Emmie Women 6.5 M Shoes Multi Color Chevron Ballet FlatsBASS DETOUR SZ 10 M Leather Loafers Brown Strap w/ Buckle Classic Comfort ShoeNEW! Sperry Women Aubrey Greige/Bronze 5M r37 pa , Aerosoles Lets Drive Loafers, Navy, 6.5 W USCLARKS brown ballet flats slide on loafers shoes 6M comfort slip on brass ring , ANTONIO MELANI DARK BLUE SOFT LEATHER LOAFER SHOE 6.5MSperry Topsider Womens Shoes NEW $90 Songfish Stripe Navy Blue Boat 7 M , Vionic Gem Caballo Flats - Women's Size 7, Navy BlueEnzo Angiolini Womens libelle Closed Toe Loafers, Black, Size 7.0 Km87 , Brand New Custom Made Vans Seahawk Colors, Blue, Green and Grey 7.5Breedink-Abyssinian Cat On Hearts Print Wallet CaseWomen's Reebok Zprint Run EX Running Shoes Size 6.5 US3 Color Hot Womens Flat Slip On Fashion Sneakers Shinny Loafers Shoes Plus SizeWomen's Skechers Women's D'Lites-Spark Interest Sneaker Queensland Athletic ShoesWomen's Sperry Calla Jade Sandals Promotions Flats , adidas Women's CF Advantage CL W Sneaker, Black/Black/Utility Black, 5 M US , Unique Golden Retriever Collage Print Running Shoes For Women- Free ShippingNew Nike LunarEpic Flyknit Women's Running Shoes, Size 9 (818677 301)Nike Womens Court Majestic Running Trainers 454256 Sneakers Shoe 017 , Womens Pull On Loafers Sneakers Flat Muffin Shoes Rhinestones Green Silver Chic , New Balance WX608V4W Athletic Cross Training Running Shoes Sneakers Women's Sz 8 , Propét Women's Stability X Strap SneakerReebok Women's Vintage 1990s Comfort Walk DMX Shoe 11-26186 White/Grey sz. 6.5Nike Air Max Torch 4 Womens Running Training Shoes Size 9.5 Black Gray
"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."