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.ZigiSoho Women's Multi Color Jeweled Flats 6Women’s Lily Holt Shoes Brown Suede Sz 10 , Kelly & Katie Womens lovelian Closed Toe Loafers Navy Size 9.0 O9r4 , MICHAEL ANTONIO PORTIA CONTRAST TOE BALLET FLAT , Bass Rachel Antonoff Lewis heel floral oxfords white sz 7M in box retail $139 , Kelly & Katie Womens Cigola Pointed Toe Loafers light pink Size 9.0 7Zpk , Womens MERRELL Size 8.5 Siren Cassia Beige Suede Leather Mary Jane Sport ShoesBALLERINES CHAUSSURES GEOX "RIUTA" TAILLE 37 EN EXCELLENT ÉTATMARCO TOZZI Women's Slip-Ons, Black, Rubber Sole, Fabric NEWJOE N JOYCE Palma Espadrilles - Black White Blue Gray Beige Red , Womens 11 M Crocs Carlie Pink Lemonade Jelly Clogs Shoes Sandals T-Strap ComfortSteve Madden Womens "Studlyy" Silver Metallic Studded Loafer Flats Shoe Size 6.5Oliberte Mbozi (Rustic Brown Pullup) Women's Flats (US 10) - MSRP $115.00 , Amalfi By Rangoni Womens Flats 9B White Beige Italy Leather Jeweled Bit Slip OnJeffrey Campbell Wunder Black Velvet White Pointed Toe D'Orsay Slip On Slides , Bob Marley High top Custom canvas shoesTraditional US 6-12 Indian Women Shoes Designer Blue Mojari Ballerinas , Skechers Leather Pink Purple Silver Womens Sneaker Tennis Shoes Womens sz 8 MedWomens MOZO Blue Sz 9 Sport Suede Canvas Slip On Shoes *A944 , New!!! Women's Skechers 14475 GOGA MAX navy slip on 411L ss , Women's US 10 Nike Air Zoom Pegasus 33 Shield 849567-500 Water Resistant A6Clarks Evianna Fuse Black US Size 8.5 M - FREE SHIPPING - BRAND NEWPuma Athletic Running Shoes Women's Black & Pink Size 7 , PUMA 36596501 Womens Vikky RG Platform- Choose SZ/Color.Womens Nike AIR JORDAN 1 RETRO LOW NS NRG Shoes "Python" AJ6004 010 -Sz 7.5 -New , New Balance WT474LP Gray/Blue Women's Running All Terrain Shoes Size 9.5 B , Converse Chuck Taylor All Star Brea High White (555829C) , New Women Flowers Leather Casual Sneakers Pull On Leisure Sport Shoes LoafersSKECHERS Womens Shape-Ups Athletic Walking Shoes White Silver Size 10 Leather03-84 BROOKS Launch 4 Running ELECTRIC BLUE/TOREADOR/WHITE SIZE 9B
"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."