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.Dansko Victoria Canvas Clogs Women 40 9.5-10 Floral Vegan Jute Professional , BC Footwear Women's Brown Leather Clogs Mules Size 6 COMFY , Boston Design Studio Rainbow Striped Flats Size 9EASY SPIRIT E 360 BROWN genuine LEATHER SLIPON COMFORT SHOES once worn 8 8.5 m , Blowfish Womens Cayo Gray Casual Shoes Sneakers 7.5 Medium (B,M) BHFO 7906 , New Women's Skechers 34491 Bobs Stand By Me Flats - Pink Size 6 (B6)COLE HAAN COUNTRY ~BRAZIL~ BEIGE SUEDE LEATHER LOAFERS ~ 9-1/2 BWomens 6.5 Naturalizer Ballet Slipper Type ShoeWomen's Keen Harvest Mary-jane Shoe Size 7 Pink Stripe Multi Slip On Touch Close , Comfortiva Womens grace Closed Toe Slide Flats, Rose Gold, Size 10.0 5skJEUC Merrell Shoes ENCORE ICE STONE Wmn US 8 Brown Suede Slip-On Lined Walking A6New Balance Women's WW577BK Black Walking Sneaker GOOD , Merrell Mix Master Move Glide 2 Wild Dove Orange Running LIght Shoes Women's 11 , EVERLAST STACEY WOMENS/LADIES SHOES/SLIP ONS/SNEAKERS CASUAL/SPORT/FASHION!MARC by MARC JACOBS BLACK PATENT LEATHER SLINGBACK FLATS Sz 39M , Sesto Women's Black Slingback Espadrille Made in Spain Size 9Vince Camuto Signature Women's Vie Denim Shell Salmon Snake Espadrille Flat , Merrell Cypress Chocolate Women's Hiking Trail Casual Shoes US 8,NEW BALANCE 645 All Terrain Walking Trail Hike Leather Shoes Womens Size 5 ?b5 , SC35 Louiza Perforated Slip-On Sneakers, Light GreySkechers Flex Appeal 2.0 High Energy Womens Sz11 Wide Rose Sneakers Shoes F4-236Women's brooks caldera running shoes- women’s New Listing Athletic Shoes , Women's Nubuck Leather Casual Embroidered Shoes The Queen Of Quality Flats , Reebok Women's FREESTYLE HI COLOR BOMB Shoes Mineral Mist BS7860 b , Preowned Zeus Diesel Footwear Size: Lady 9BNIB Reebok Sublite Escape 2.0 MT Women's Running Shoe, Gravel/black/pink , RARE Nike Women’s Sky Force Sneaker Wedge Black Metallic Size 7.5 629746-001 EUC , EUC Nike PEGASUS 31 654486-600 Women Sz 8 Pink Running Shoes A6Teva Womens DE LA Vina Leather Waterproof High Casual Boots Size 7.5Merrell Granite Gray Suede Leather Sneakers Casual J42282 Women's US 9.5
"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."