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.Bearpaw Womens jolene Suede Closed Toe Clogs , R2 snakeskin and gold ballet flats sz 6.5 - worn once , Privo Clarks Slip On Casual Shoes Womens Size 7.5 M 5481 SHA6 , Nine West Womens Girlsnite Synthetic Ballet Flat- Select SZ/Color. , Women's Cole Haan brown Leather Clogs Shoes Water Proof Size 7.5J. Renee fancy gold mesh wedged loafers size 8 N , Dune London Hubble Black Leather Women's Slip On Flats Size US 5 M , NEW NWT CROCS FREESAIL LINED CLOGS ESPRESSO BROWN 6 7 8 9 10 11 winter shoes , Aerosoles Girl Talk Flats Size 8.5 D5 68 PKarl Lagerfeld Paris Womens Shupet Black Ballet Flats 8.5 Medium (B,M) BHFO 2187 , Marc Jacobs Women's US 8 Black Leather Penny Loafer Flats Slip On Shoes , Jack Rogers Womens Lucie Ballet Flat- Pick SZ/Color. , Women's Aerosmith Black & White Canvas Sneakers US Size 10 , Salvatore Ferragamo Patent Leather Leopard Animal Print Cap Toe Shoes 8 AA , New! Women's Skechers Flex Appeal 2.0 Insights 12765 Walking Shoes BBK 68i pc , Womens SKECHERS shoes Size 5.5M In VERY GOOD CONDITION339) , Brooks Glycerin G13 Womens Black Purple Yellow Running Sneakers Shoes Size 7.5Puma smash wns L halogen blue free shippingMizuno sz 9M Wave Rider 8 white navy blue womens ladies running athletic shoes , Steve Madden Ecentrc Quilted Slip Ons-Women's sz 7.5 M BlackPuma Women's Driving Shoes Black Suede White Leather Accents Sz US 6New Balance WT20GP Minumus Vibram Trail Running Barefoot Sneakers Womens US 7 BWomen's NEW..SANITA..5 BLACK..ORIGINAL..PROF. PRESLEY..PRINTED METALLIC LEATHER High Quality Flats , Vans Women SK8-Hi Slim blue true white aruba VN02R2HGFNEW NIB BOUTIQUE 9 Kelly Green Perforated Leather KATELYN Stud Sneakers $190Womens New Balance WR790BC Running/Walking Sneakers 9.5 Multicolor8.5 M GByGuess Womans Hightop Athletic Casual Shoes Black Zip Sweater Fabric , NIKE WMNS AIR MAX THEA PRINT Lt Blue Lacquer/White-Clear Water -599408 401-Rider Women's Monza III Thong Sandal Black/Grey SandalsAsics GT-2000 Shoes Women's Size 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."