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 US 7.5 black slingback flats shoesClarks Women's Brown Pebbled Leather Mule Loafer Slides Slip-on Size 7M 74126 , White Mountain Womens Taupe Suede Leather Loafers Shoes Size 8.5[EL] Women's Fashion Point Flat Shoes Ballet Shoes Slippers Casual ShoesPatagonia Gilia low tide Women's Green Slip on Shoes Sz USA 10/(#Lot2 , STUDY women's red patent leather/fleece shoes punk rock hipster ELMO NWOTNatural Soul Women's Black Leather Low Wedge Mary Jane Shoes Size / US 8 , NICE Women's Cole Haan Country Slip-on Slides Shoes Loafers Brown Leather-7 AAClarks AZELLA THEONI Womens Red LEA Casual Slip On Comfort SHOES SZ 9.0 M D8030 , STEVE MADDEN LUXE SLIP ON OXFORDS/FLATS-SPARKLING-SZ 8.5-UNBEATABLE PRICESLauren Ralph Lauren Women's Black Leather Croc Print Horsebit Loafers Shoes 7.5B , Cochni Brown Leather Animal Textured Pump w/ Jeweled back Size 36 US Size 5.5Cushe Treat Mary Jane Purple Plum Ballet Flats Womens Shoes Size 7 , NICE Women's SAS Tri-Pad Comfort Low Wedge Shoes Slip-on Loafers Black-USA-8.5 SYosi Samra Vienna 2 Pointed Toe Flat- Women's Size 7, Black , Skechers BOBS Women's Plush Lite-Peek Ballet Flat Black/Black 8 M US , Soludos Women's Shoes Loafer Embroidered Suede Black Size 9 FREE SHIPPING!COLE HAAN "Pinch" Maine Classic Black Leather Loafers-Size 11B , Rocket Dog Union Jack Flag UK of Great Britain Woman Flats Sz 6.5 USED , The North Face Women's Ultra 109 GTX Hike Trail Shoe Steeple Grey/Balsam Blue 8M , Steve Madden Mens Pipeur Black Fashion Sneakers Shoes 9 Narrow (B) BHFO 2062 , THE NORTH FACE Women 8 M Gray Northotic Comfort Walkers Athletic Casual ShoesConverse All Star Gray Women’s US Size 7 EUC with original boxWomen's JANA Sneakers 23603 Noir Good Reputation Over The World FlatsADIDAS Neo Lite Racer Slip On Women's Comfort Shoes Sneakers size 8.5 8 1/2 , New Balance Industrial 627 Women's Work Shoes Steel Toe Size 6.5 WID627GLConverse All Star Chuck Taylor Sneakers Hello Kitty pink canvas Size 11 1/2NEW NIKE Air Max Thea Print Running Shoes WOMENS 7 Blue Spark 599408-405 $105 , Converse Womens Chuck Taylor All Star Low Top Aruba Blue Sneakers 7M NEW IN BOX , Womens Skechers 32574 Bobs Plush Dogs Dog Lovers Go Fetch Slip On Casual Shoe
"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."