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.LIFESTRIDE Shoe 8.5 8 1/2 Brown Flat Low Wedge Heel Ballet Style Slip OnDansko Green Leather Slip On Mule Nursing Professional Clogs Womans Size 6 36Sperry Womens Top Sider Angelfish Sand Serape Leather Stripe Size 8M (Worn Once)CLAUDIA CIUTI Made in Italy, Black Suede Women's Shoes, US Size 9,5MSANUK DONNA PALMA HOT TURQUOISE SIDEWALK SURFER SHOES, SIZE US 7/ ~NWTWomen's Taos Tango Drees Pump Mary Jane Casual Shoe 9 US , NIB Anne Klein Laise Brown Leather Loafer 9.5M-Org $69TX-533 NIKE SHOX 2008 WHITE RUNNING SHOES WOMEN'S SIZE 7Womens Flats Hollow Out Hidden Wedge Heel Slip On Loafers Sneakers Shoes Us Sz , VTG Original B.U.M. Equipment Womens 8.5M Green Canvas High Tops VGC!!! , Womens NIKE T LITE VIII Running Court Training Athletic Sneakers 7M 386508-111Nike Womens Air Zoom Pegasus 34 Black/Dark/Grey/Anthracite Running Shoes SizePair of Foot-Joy Green-Joys Ladies Golf Shoes Size 8M ()Converse All Star Brown Suede HighTop Sz 8 M Chucks Shearling Sneakers?Nike Womens Dual Fusion Lite Yellow Size 8.5 Walking Running Shoes , Converse Chuck Taylor All Star High Top Rhinestone size 7 , Adidas ClimaWarm Modulation W Running Shoes Black Silver In Box Sz 6.5 $85 RetNew Adidas Womens BB2344 Black Pink White Running, Cross Training 8.5 6.5 nmd , MERRELL Tetra Women's Solid Black Clogs Slip Ons 8 , Women's Cole Haan Bowie Slip On Sneaker Size 9B , NIKE Classic Retro Cortez Nylon Suede Sneakers Shoes SZ 7 NEW , ASICS Womens Blue Running Shoes Size 11 (28147)Himalayan Cat Print Running Shoes For Women-Free ShippingCrosskix Hybrid APX Blackwater 4M/6W Water Shoes Unisex EVA Black Airflow , VANS Rata Vulc SF Dress Blues/Gum Slip On Skate Shoes WOMEN'S Size 8 , Pre-Owned Women's KEEN "Prescott" Brown/Green Leather Ballet Flats sz 8,Crocs Women's Work Flat Food Service Shoe, Black, 8 M US , Asics Gel Contend 4 Womens 7.5 Ortholite Running Training Shoes NIB T765Q PMASICS WOMEN'S GEL-EXALT 3 T666N RUNNING SHOES PINK SZ 12.0 M PRE OWNED D4788 , NEW IN THE BOX VANS CLASSIC SLIP-ON BLACK/BLACK VN000EYEBKA FOR WOMEN
"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."