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.Clarks Bendables Brown Faux Alligator print slip-on loafers, Woman's size 6CROCS "KADEE REALTREE" CHOCOLATE/BERRY SHOES WOMEN 8 medium NEW , �Steven by Steve Madden 10 BLACK MADEE-R Slip-On Loafer Flats Shoes NIB , NEW! Penny Loves Kenny "Farrah" Fuchsia Ballet Shoe 7.5MNine West Starship Black Womens Shoes Size 7 M Flats MSRP $69 , Womens 8 M Eddie Bauer Vtg Brown Leather Woven Ballet Flats Shoes Loafer Slip-OnORTHOFEET Women NWOB Monk Strap Hook & Loop Loafers Size 7W Black LeatherMephisto Leather Olive Green Loafer Wedge Shoes Women's Size 8.5 , Reebok Crossfit Nano 5.0 Built W/Kevlar Pink Gray Shoes Womens Sz 7 , Adidas Jett Breeze Running Shoes, #G48171, Grey/Pink/Yellow, Women's US 7.5Crocs Women's Drew Barrymore Classic Chevron Clog - Choose SZ/ColorDr. Scholl’s Womens Beatrice Black Fashion Shoes Size 6.5 (407687) , ADIDAS NEO VIBE COMPLETE LOW SHOES ENHANCED COMFORT SYSTEM SIZE 6 YOGA TRAINING , Women's Mizuno Wave Elixir White/Gray/Green Running Shoes Size 9 NICE!MINT Saucony Run Dry Size 7.5 US Womens Freedom ISO Blue Citron Running ShoesMia Zoe Statement Bow Sneakers 8 Womens Black Faux Leather Shoes , Nike Roshe One GS 599729 302 HyperTurq, Jade, White size 4.5YWomens 9 40.5 Nike Air Max Run Lite 5 Running Shoes 631664-007 Gray Pink Blue , Saucony Cohesion Size 10.5 Silver Blue Green Running Training Shoes For WomenPuma Platform Trace Block - Purple - Womens , Women's Womens Nike Roshe Size 6.5 Utmost In Convenience Athletic ShoesWomen's GRAY SHOES WOMENS SIZE 8 For Your Selection Flats , Nike Air Max 1 Pinnacle Womens Cool Gray Size 6 Casual Shoes 839608 002 , VINCE CAMUTO CAELYN Black Patent Designer Pumps Heels, Classics 8.5 MNew Women's Inov-8 Roadclaw 275 Running Shoes US 7.5 Pink $130 Training , Womens Nike Lunar Glide Size 7.5- Black , Saucony Women's Grid Marauder 2 Running Shoes Sizes 6, 6.5, 7, 8 & 8.5 , CONVERSE CHUCK TAYLOR CT HI RISE BOOT WOOLRICH WMNS SZ 7.5 YELLOW BLACK 549686C , Under Armour Spine RPM Storm Gray Pink Running Shoes 1238325-019 Women’s Size 7New Womens Shoes Fashion Casual Sneakers 6 White Black Skechers Street Zebra ,
"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."