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.BOC Born Concept Women's White Slip On Round Toe Ballet Flats Size US 7.5 , J Jill Perforated Suede Driving Moccasins Loafers Size 6.5 $98 , Ballerines RAXMAX Velours Noir et Corail T 36 TBE , Women's LANDS END Black Suede Slip On, Fleece Lined Flats / Clogs, Size 7 BCole Haan 8 Narrow Driving Loafer Moccs Gold Leather Women , Minnetonka Moccasins Dark Navy Leather Womens Slip On Moc Loafer Shoes Size 7.5 , WOMENS NURTURE AVANA NAVY PATENT LEATHER Suede Ballet Bow Heels Sz 6.5 M NEW 627Ladies BCBG Red Suede Ballet Flats Size 8.5NEW Beverly Feldman Shoes Sz 35 5 Beige Animal Print Leather Ballet FlatsNew Women's Skechers BOBS Plush - Peace and Love (33645) Size 8.5 (L10) , New Balance Womens - Black Walking Shoes Size 9.5 (316934)Women's Champion Muscle Toning Shoes Size US 11, /2,$77.99 Hello Kitty Womens Sofia (gold) MW1D01-GLDClarks Leather Perforated Flats Medora Nina Red 6M NEW A287335Sketchers Street Women's Lola Metal Mayhem Sneakers White/Silver US size 9.5MNIKE DUAL FUSION TRAINER 2 631459 600 Womens Size 5.5Nike Women 9 Pegasus Running Shoes Blue Gray Athletic Oxford Vented , Avia GFC REINA - Blue - WomensWMNS Air Force 1 HI FW QS City Pack NYC Women’s 7 Bone Quilted Map , Nike Pink Metallic Gold Sparkle Sky High Top Dunk Sneakers Sz 8 , Women's Flat UNIONBAY Waldorf Beige Superior FlatsMerrell Proterra Sports Womens Outdoors Hiking Trekking Shoes Pink US8.5,US9Skechers 49530 Relaxed Fit Memory Foam Slip On Sneakers Choose Sz/ColorFuntasma Women's Gogo 150 Ankle Boot Silver Stretch Polyurethane Ankle BootsNIKE FLYKNIT LUNAR 3 SZ: WMNS 5.5 (698182 303) RETAIL: $150.00 , Adidas Women's Supernova ST Athletic Running Shoes Easy Blue/White/Easy CoralNIKE Lunarglide 8 Womens Sizes 6 7 Shoes Black White AA8677 001 , Nike Air Max IVO. Brand new (GS). Available Kids/Women sizes: 4.5y/6 & 5y/6.5 , WOMEN'S PUMA FIERCE BRIGHT 189738 03 PUMA WHITE BRAND NEW DEADSTOCKadidas Women's W Adipower S Boost II Spikeless Golf Shoe, Size 5.5 ,
"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."