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.Womens SAS Slip On Brown Casual Comfort Loafers Size 9.5WAJ Valenci BLACK SHOES WOMENS SIZE 8 1/2 M , Bama Womens Size 39 Loafers Black Slip On Pumps Dress Shoes Casual Walking Work , L'Artiste Burbank Clogs - Women's Size 7.5/8, Brown (REPAIR)MUNRO AMERICAN WOMENS US 7.5N TAN SUEDE LEATHER Oxford Walking Shoe USA , Seychelle's Weekenders Navy Blue Suede Loafers Women's Shoes Size 7 M NEWWhite Mountain Sarlow Round Toe Flats 363, Black/Burn/Smooth, 8 USLady shoes flats 3/4" heel leather by heavenly comfort 9 WW red bow on toeVionic Womens Elation Bayside Heeled Slip On Clog Shoes, Cinnamon, US 6 , Munro American Wedge Ladies Burgandy Wine Shoes Size 9.5MWomen’s Clarks Black Leather Slip-On Shoes Clogs Mules US 8 M Brazil 35961Women's KEEN Brown Leather Slip-Ons (Size: 9.5 M) , Puma Roma Linen Women's Whisper White-Powder Blue Shoes Size 8.5 US Casual SportBritish Womens Slip On Leather Low Block Heels Tassels Mules Shoes Casual NewWomens 7.5 M jambu capri brown leather suede clogs shoes booties faux fur wedgeWomen's Sperry Top Sider Laguna Dark Tan/Greig Boat Shoes Size 6 New with Box!!!Adidas Cheer Sequence Cheerleading Shoe NIBReebok Womens SKYSCAPE VIVA CV SAKORI Low Top, Collegiate Navy/White, Size 9.0 R , New Balance Womens White Running Shoes Size 11 (271153) , Women Comfort Sneakers Lightweight Sequin Hologram Style Shiny Bling Party Shoes , BZees Women's Runaround Slip-On Athletic Sandal, Black 22, 9 M USNew Balance Zante V3 WZANTBB3 Womens Size 10.5BMBT Women's Afiya Slip-On Blue/Lime Authenticator Verified! 38 EUR (7-7.5 US)LACOSTE JOUNEW hilly billy pumps high heels alisos barbuda spLacoste Ziane BL 1 SPW Navy - Womens - Size 8 B , adidas Ultraboost X All Terrain LTD Shoes - Ash Pearl/Trace Orange EUC Womens 9 , Nike Dunk Low GS – White/Metallic Silver Pink VTG Kids 4.5Y Womens 6 SneakersVans ERA 59 C&L Black/Gum Women's Shoes 8 , REEBOK SYNTHETIC GREY PINK SMOOTH FIT ZIGNANO WOMAN'S RUNNING JOGGER SHOE SZ 7.5New Balance 1865v1 Gray Orange Walking Shoes Womens Sz 7.5 2A Narrow MINT! ,
"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."