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.Women’s CAMPER Lt. Blue Pink Leather Shoe Retro Bowling Patchwork Mismatch Sz 9 , Ryka Womens Tensile Blueberry/White Mules Size 7M , NEW Womens Tennis Shoes Size 7 Solid Black Flats Ladies Slip On Sneakers ComfortJBU ADVENTURE women's 11 Brown yellow Hiking Athletic shoesCLARKS BENDABLES BUTTON SLIP ONS FLATS BROWN LEATHER 7 M LOAFER OXFORD 35063 EUCFEUD made in India nude leather slip on loafer studded sz 5 , Mary Jane Shoes Elegant Large Size pearl Ballet Flats Womens ballerinas US 0-17Gorgeous Black Leather Brighton Flats Shoes Size 6 1/2 , Merrell Skynight Burnt Red Women's SZ 7.5 M Slip On Loafers Flats Walking Shoes , Nine West Aweso Pointed-Toe Ballet Flats 719, Black Multi Leather, 5 USSAS Clog Women's Shoes 7.5 narrow , SAS Free Time Size 8 W Wide Black Suede Leather Oxford Walking Shoes Women's USABETULA Birkenstock Womens Brown Leather Slip On Mules Closed Toe Flats Size 8Aerosoles Womens Main Dish Closed Toe Loafers, Silver, Size 7.0 Otsg , Guess Jollie High Top Fashion Sneakers 456, White Multi, 7.5 US , Asics Hyper Rocket Girl 6 Size 10 Track Shoes Cleats Malibu Blue White Lemon NIB , WOMENS SAUCONY PROGRID GUIDE 3 GRAY WHITE BLUE RUNNING SHOES SIZE 5M G494Skechers Shape Ups Womens Walking Shoes Sz 8.5 White Blue (26) , Merrell Women's Moab Ventilator Hiking Shoe Smore Size 8M , Brooks twitch s women 11 Retail $60Hot New Summer Breathing Hole Canvas Shoes High Top Hidden Heel Casual Sneakers , Merrell Mimosa Moc Black Womens Slip on Shoes Leather Size 9.5 , Allbirds Sz 7 Women's Wool Runners dark gray wool with white soles. GREAT shape! , New Balance Women’s 405 White Leather Walking Training Shoes Size US 10ASICS Gel-Surveyor 5 Women's Aqua Silver Sneakers Running Shoes US 7.5 B798 , Keds Women's Kickstart Perforated Leather WH56115 WHITE 8.5 8 1/2 MED MVANS ATWOOD LOW SNEAKERS WOMENS NIB CASUAL SKATE SHOES BLACK WHITE BURGUNDY , Tony Little Cheeks Lighweights Casual Athletic Footwear NIB Size 9REEBOK FURYLITE CHUKKA LTD AFRO PACK WOMEN'S RUNNING SHOES SIZE 7 RARE $150 , NWB Black SKECHERS GOWALK JOY PARADISE Shoes Sz 9 Wide Fit ~~~FREESHIPPING~~~
"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."