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.Nine West Pony Hair Sneaker Women size 7 LeopardWomen's 9M Bass Boater Loafer EUC , AGL Attilio Giusti Leombruni Black Suede Cap Toe Ballet Flats Size 37.5 7.5PROPET Ped Rx Red Leather Mary Jane Orthotic Walking Shoes WPRX35 Size 12 W (D) , NEW J Crew Harper Leather Tassel Mules Slides Flats Sz 7.5 Ivory RARE!! J.CrewKlogs Bambi Women's Display Model Shoes Black Wigwam 7.5 WRockport Cobb Hill Galway Perforated Gigi Loafers, Women's Size 7.5 N, Grey , Vans Solana Women's Peach Fashion Sneakers 10M , Billabong Women's Addy Fashion Sneaker Seagrass Size 7.0 sGcj , Chaco Women's 7.5 Sport Loafers Black Leather Zaagh Gunnison VibramConverse All Star Chuck Taylor Low Tops Womens 7 metallic red Elastic Back , Aerosoles Women's Apple Sawce Mule Shoes Black Faux Leather Size 7.5 M USConverse Ct Women's Print Ox Low Top Fashion Sneaker Shoes White Multi 5 M , Brooks Ravenna 9 DNA Running 1202691B452 Women’s Size 9PUMA BASKET MMQ SHOES WOMEN'S SIZE 10 1/2 , Skechers Women's GOrun 600 Running Shoe SZ 8 , LL Bean Portlander Free Flex Boat Shoes Sneakers Sz 9.5 M Stretch Mesh Blue EUCSANUK KAT NIP OLIVE SIDEWALK SLIP ON US 9.5 / / NWT , Bernie Mev Women's Mid Olympia Fashion Sneaker, Black, 37 EU/6.5-7 M US , Nike Lunarfly 3 Womens Running Shoes Size 8.5M Pink Grey Sneakers -2998 , Vans Women's Size 6.5 Cutter White and Black Leather Skater Shoes Hipster VGWomen's Vince Grey Flat Shoes 7.5 Low-priced FlatsNIKE Air Zoom Strong Womens Sz 8 Shoes Gray Black 843975 100NWT Adidas Volleio Womens Court Shoes Sneakers 11 White/Black/Silver MSRP$110Saucony Ride 7 Womens Running Athletic Shoes Purple Gray Yellow Size 6.5 Narrow , Easy Spirit Women's Explorie SneakerNike Benassi Cuff Lux White NikeLab Sandal 819684-100 Women's Size 6 , Nike Roshe One GS Rosherun Blue Black White Kid Youth Women Shoes 599728-420 , BNIB WOMENS ADIDAS PUREBOOST XPOSE RUNNING SHOE SNEAKER SIZE 11 GREY , Ladies Black and Gray Merrell Breathable Hiking Shoes Size US 9- Euro 40 ,
"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."