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.Ladies Loafers by Lands End, Size 7B, Black Leather,EXCDKORKS BY KORK-EASE Caramel Leather Studded Fashion Ballet Flats- 6.5 M 37 , Klogs Women's Audrey Clogs Black Smooth Leather Display Model 7 W , Women's SAS Metallic Colored Tip Dress Flats Size 7Lucky Brand Womens Size 7.5M Emmie Flats Leather Round Toe Ballet Black NWOB , NIB SPERRY TOP SIDER SEASIDE NAUTICAL PERF BLACK SLIP ON FLATS SHOES 7 7.5Geox Fashion Sneakers Burgundy Leather Women 10 Medium (B, M) , Lotto Forza, Girl's, Size 7, Pink & Yellow, CleatsRetro Womens Tassels Leather Casual Slip On Flats Mules Shoes Square Toe OxfordsH By Halston Slip On Flats 7 Medium Gold Perforated Leather Leah NEWSPERRY TOP SIDER Women Taupe Coil Mia Suede Leather Boat Shoes $76 Retail Size 9Skechers Bobs Highlights Sand Sparkle Women's Slip on, Natural, Size 8.5 Wz0a , Fashion Womens Tassel Bowknot Slip On Hidden Wedge Sneaker Loafers Creeper ShoesFootJoy Comfort Leather White / Tan Oxford Golf Shoes Women's Size 7.5 W , Clarks Haley Stork Comfrot Flat Sneakers 537, Taupe, 10 US / 41.5 EU , Women's adidas energy boost (Women 7.5US) Durable Athletic ShoesWomen's Rebecca Minkoff leather Flats 9m Fast Shipping Flats , Women's M. Gemi Driving Mocs Quality Product Flats , Women's Nike Free RN Motion FK 2017 Size 12 (880846 005) Wolf Grey/Cool Grey , Reebok FS Hi Jersey Freestyle Mid Fitness Training Sneakers Shoes Womens 7New Under Armour Women's Dash 2 Running Shoes - Size 6 - Black / WhiteAna Lublin ESTELA_BEIGE sneaker Women's - colour Brown US , New Women Vans Authentic Black Skateboarding Shoes Classic Canvas size US 10Wmns Nike Internationalist Print Black White Womens Running Shoes 833814-001Clarks Women's Cheyn Marie Loafer Grey Leather/Full Grain LeatherNIKE Zoom Vomero+ 8 Sneakers Training Running Athletic Shoes Womens 10.5 Pink , adidas Women's NEO Cloudfoam Advantage Stripe Court ShoeNew Women's Platform High Top Heel C50 7-Holes Taller Insole Fashion Sneakers , Nike 615968 Womens Winter Roshe Run Hi Top Sneakerboot Ankle BootPONY Womens Top Star Lo Core CVS Sneakers Light Pink Canvas Skater Size 7 ,
"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."