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.Jessica Simpson Womens Deonne Brown Booties Shoes 11 Medium (B,M) BHFO 2191SIMPLE 'Planet Walkers' Womens Size 7 Black Woven Leather Mule Comfort Clogs , Earth Women's Butterfly Ballet Flat -Red Plum Sz. 6.5 BWolky Womens Green Wingtip Patent Leather Walking Slip On Shoe Size US 8 , Easy Street Women's Nova Mule, Burgundy/Burgundy Matte, 6.5 M USLADIES TENDER TOOTSIES LEATHER RIPTAPE STRAP SHOE STYLE - 276017 , Antonio Melani GiGi Calfhair Flats Size 8M Black/Tan NEW with BoxNIB NEW Free People Faux Fur Sonnet Clog Black size 39 US 9 , Fashion Women Comfy Modern Jazz Hip Hop Dance Shoes Breathable Sneakers Soft 12 , Aravon Women's Black Leather Shoes Size 8 D Made in Brazil , ASICS Womens Gray Running Shoes Size 8 (11145) , Nike - Sneakers - Ladies Size 7.5 - hot pink/White 749178- 602 , Men Sanuk Chiba Sidewalk Surfer Slip On SMF1047 Black/Charcoal 100% Original NewNEW DEARFOAMS MEMORY FOAM MOCCASIN SLIPPERS MENS M SLIP ON SLIPPERS SIZE 9-10 , SKECHERS SHAPE-UPS 10M gray suede & mesh irredescent pink purple accents xlnt. , Saucony Echelon 5 Running Shoes Size 10 Pink Gray Shoes Mesh S10276-1 WomensAdidas formotion supernova G97326 Women Shoes US Size 8 , NIKE In Season TR 7 Women's Size 10 Black Mesh Training Athletic Shoes F5-572Merrell Siren Sport Womens 7.5 M Brown Beige Hiking Shoes J16962 Leather Vibram , Women's American Eagle flats size 7 Unusual FlatsNew Puma Basket Heart Patent WNS GRAY Ribbon Fashion Sneakers 363073 12Nike Wmns Air Max 90 Suede Orange Grey Women Running Shoes Sneakers 325213-801 , ADIDAS KANADIA 7 TR TRAIL RUNNING SHOES WOMEN'S 10 M RTL $80 PINKEasy Spirit Women's Romy Sneaker,White Multi,7.5 MASICS Womens T853n.4949 Blue Walking Shoes Size 10.5 (34782) , Adidas Women Running Shoes Galaxy 4 Training Work Out Fitness New Gym B43832 RunNew Balance Women's Razah V1 Running Shoe , ASICS Gel-Nimbus 18 Running Shoes-Women's sz 12 Grey , Nike Womens Flex Supreme TR 3 Cross Training Womens Shoes 683138 604 Sz 8 PInkHi-Tec Penrith Low WP Steel Grey/Aqua Womens US 7.5 Hiking Shoe NIB
"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."