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.NEW MINNETONKA CHESTNUT BROWN LEATHER MOCCASIN BOAT SHOES SZ 5 NWOT RET$45Faded Glory Ballet Flats size 8 Taupe brown Leatherette w/ Chelsea Bow , Børn Born Brown Leather Square Toe Clogs Mules Slides Heels Size US 9Naturalizer Womens Blue Yarkona Mary Jane Casual Walking Shoes: Sz 7.5Easy Spirit Women's Gizela3 Ballet Flat, Natural, Size 6.5 , Women's Sam Edelman Fara Blue Flats Size 5 M , Propet Sandal Walker Mary Jane T Strap Leather White Womens Shoes Size 9.5 W (D)6 Gold Beaded Flats Handmade Silk Bollywood Indian Khussa Wedding Bridal ShoesCLARKS Womens Kinzie Leather Closed Toe Loafers Black Combi Size 9.0 6e70Dr Martens Womens Oxford Shoes Size 6 uk Brown Leather , Calvin Klein Jeans GABY slip on SHINY NYLON/SUEDE BLACk sale re9184 , Dolce Vita Elodie Black Womens Shoes Size 8 M Flats MSRP $120 , Dansko Vegan Valerie Khaki Tan Canvas Mary Jane Clogs US 9.5 /10 Very Nice , New Women's Skechers 33934 Bobs Plush Shimmer & Shine Casual Flats Sz 7.5 (M4) , BELLES CONVERSE BLEUES MARINE T 36 TTBE ACH IMM FP RED MOND RELAY A SAIFlossy Luna Women's Classic Casual Summer Slip-On Espadrilles Plimsols Navy , Adrienne Vittadini Womens Alvine Leather Closed Toe Slide Black Size 10.0 ELb5Propet Women Billie W5100 Light weight Walking Sneaker Shoes WHITE TURQUOISE 7MNew Women’s Black PASTRY Hi-top Sneakers Size 8Bella Vita Womens Emilie BlackSuede/GreyFlannel Walking Shoes Size 9 (A, N)Minnetonka Women's Kilty Suede Moc Hardsole Brown Suede/Arizona Fabric Suede , New! Women's ASICS GT 1000 5 Running Shoes Black SZ 9.5 T7A9N K10Nike Air Zoom 90 IT Golf Shoes Black White Womens Size 7 , Jambu Womens Spain Walking Shoe- Select SZ/Color. , Skechers Women's Gratis High-Class Sneaker White/Silver Size 5 MMerrell Capra Bolt BOA Lacing Athletic Hiking Running Shoes J35892 Women 8.5Demonia Women's Creeper 118 CreeperNIKE WOMEN'S ROSHE LD-1000 KJCRD SZ 7 WHITE/GREY/PLATINUM SHOES 819845 100 , Reebok Women's YourFlex Train 9.0 MT Athletic Shoe - Silver/Mint , Women's Nike Lunarhyper Workout XT US 9 529951-300 Black Silver Green Trainer A2 ,
"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."