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 2 PAIR BASS BETSY LOAFER SLIP ON SIZE 9 M GOLD & FRENCH BLUE , NEW- TOMMY BAHAMA- SIZE 11 GOLD METALLIC VIONNA SLIP ON LOAFERS , NWT Anne Klein BK 7M HealsWomen’s Sperry Top-Siders Leopard Print Size 7M Shoes Loafers , Natural Soul by Naturalizer women leather front zip casual LUXE shoes 7.5 blackCROCS Women's Brown Ballet Flats Slip-On Shoes Size 10 , SAS TRIPAD COMFORT Beige SHOES WOMENS SIZE 7 1/2 M , Women's Dune London Mittle Ballet Flat Quilted Leather Cap Toe Shoes Sz. 7M /38 , Clarks Artisan Kessa Betty Loafers Womens Size 10 M Dark Brown Leather ShoesG250 - Luxury Handmade Genuine Leather Shoes , CHACO Womens 7 tan leather mary jane shoes loafers slip-on sportWomen's Clarks Black Leather Horse Bit Loafers Size 6.5 MFRYE Women's Regina Ballet Flat, 8.5 US. Black , Rockport Cobb Hill Collection Gigi Almond Womens Flats Size 6M , Luxury Rebel Womens Juniper2 White Fashion Sneakers 6 Medium (B,M) BHFO 0274Reebok EasyTone Smooth Fit Women 8 White Silver Toning Running Workout Shoes , Women's Champion Muscle Toning Shoes Size US 11, /2, , STEVEN by Steve Madden Women's Triper Walking Shoe , Clarks Leisa Lacole Sandals Leather Womens Slide Shoes Low Heel , Pikolinos Jerez Black Leather Driving Mocs Loafers Shoes Women's /US 5.5- 6 , Cole Haan Air Wedges Shoes Bow Sz 7B Leather Cap Toe Black Women'sNew Balance WX623AB3 Athletic Shoes - Women's Size 9.5 B - BlackDivaz Swift Slip On Floral Summer Pumps Ladies Womens Flat Shoes Plimsoles UK3-8 , Puma Leadcat White - Womens - Size 8.5 BCATHERINE MALANDRINO WOMENS FASHION SNEAKERS (6.5) BRONZE W/WHITE SOLES STYLISHSuperga Womens 2750 Cotu Classic Grey Sage Fashion Sneaker Size 8.5 (14728) , ASICS GEL-ROCKET 7 B455N BLACK VOLLEYBALL COURT SHOES WOMENS SIZE 7.5/39EUSkechers Performance Womens Go Walk 3 Dominate Walking ShoeNIKE AIR JORDAN AJ III 3 BG RETRO WOOL PREM BG DARK GREY SHOES 6Y = Sz 7.5 WOMEN , Fila C321S Strap White Navy Red Women Casual Walking Shoes Sneakers ,
"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."