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.Clarks Artisan Mules Clogs Maroon Burgundy Leather With Buckle Women Size 7 M , NINE WEST TAN BEIGE BALLET FLATS SIZE 5 UPPER PATENT LEATHER SHOE GOLD CHAIN BOW , ARIAT Brown Leather Studded Western Boot Heeled Clogs Shoes Women size 8.5 M sho , Dansko Pro Women's Grey Prism Patent Clog Shimmer Size 40SAS USA Tripad Comfort Oxford Walking Womens Size 8.5M , **Rialto Courtney Loafer - Women's Size 8 M, BlackMadewell women shoes brown size 8.5Penny Loves Kenny Boch Ballet Flats, Women's Size 7.5, NavyNIB Bass LAVERNE Black Leather Slip-on Shoes sz 6 M NEWSperry Top Sider Women’s Size 6.5M Gold Slip On Casual Shoe NWOTSam Edelman Pemberly Black Embroidery Velvet Mules Size 10 , INC International Concepts Womens ZABBIE2 Pointed Toe, PEARL GOLD, Size 6.0Women Casual Stars Sneakers Fashion Comfortable High top Shoes White 4553_IgHush Puppies Bal Harbour Loafers -Patent Leather NEW! Cream/ Ivory. Too cute!LAUREN BY RALPH LAUREN Womens AUSTINA Ballet Flats Pink US 6.5B (EC1361817) , Dr. Andrew Weil Orthaheel Technology Fiesta Wool Mary Janes Clogs Shoes Size 5 , LADIES WOMENS SLIP ON WALKING COMFORT LIGHT WEIGHT SPORT SHOES TRAINER FLEXI GO , SOFTSPOTS BONNIE LITE WOMENS NAVY LEATHER COMFORT HAND SEWN 7.5 MWomens SPERRY TOP-SIDER SAHARA kahki leather boat shoes sz. 6 M $99 , New Womens Summer Breathable Wedge Heels Pumps Pointed Toe Sneakers Casual Shoes , Stubbs & Wootton NYC Bird 9 1/2 9.5 Slippers - Black Linen $495 , C9 Champion Women's Limit 3.0 Performance Athletic Shoes Blue - 11womens tennis shoes navy blue size 10 memory foamSKECHERS Intuition 21751 Taupe Leather Suede Sneakers Womens Walking Shoes 9.5M , Asics Lazerbeam RB MG Flash Green Orange Kid Junior Preschool Running C728N-8530Converse All Star Sneakers Lemon/Orange Size 8 , K-Swiss Women's Modern High P Sneaker, Beaujolais/Off White, 6.5 M US , Nike Women's Free 5.0 TR FIT PRT Running Training GREY/BLCK/VOLT 704695 015 SZ 7 , Puma Trinomic Disc Womens Black and White Trainers Slip On Shoes 358071 02 D100Guess Alexea Casual Platform Fashion Sneakers 292, Gold Multi, 7 US ,
"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."