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.Soda Women's Perforated Slip On Elastic Panel Athletic Fashion Sneaker TRACER-GDOLCE BY MOJO MOXY BUTTERCUP ROSE FLATS - NWOB -SIZE 9M - CUTE SHOES! NEW!! , NEW Womens Tennis Shoes Size 6 Black Mary Janes Flats Canvas Casual SneakersWOMENS MINNETONKA BEADED THUNDERBIRD BROWN SUEDE HARD SOLE TASSEL MOCCASIN SZ 8 , Antonio Melani Women's 6 M Black Real Bovine Hair Leather Ballet Flats "Graham"Sanita Professional Clog Women size 41/10-10.5 Black Leather , Ecco Shade Bike Toe 20023 Black Leather Slip On Casual Dress Loafer 5/5.5 38Brand New With Box Opening ceremony Slip On Shoes size 36Sam Edelman Rodney Flat - Women's Size 8.5M Gold , Camper Womens leather loafer size , GEE WAWA Anthropologie Scalloped Blue Crackled Leather Ballet Flats WOMENS SZ 7 , ABEO 24/7 Eden Orthotic Shoe Black Sz 9M , Vans Women's Authentic Lo Pro Floral Coriander True White, SIZE 8, EUCNEW EASY SPIRIT WOMEN'S KOTA SHOES Sz 7.5 , Skechers Sassie Heirloom Size 9.5 Gray Glitter Women's Sneakers Slip On Shoes , Nike Shox 324749-111 Turbo VII White & Silver Running Shoes Women's Size 6.5 , Women's Jeffrey Campbell Sonnet Flat 7 Online Shopping Flats , Women Adidas BY2949 Superstar Slip on Running shoes white Sneakers , Skechers 31671 Cali Womens Flex Appeal 2.0-Start up Sport Sandalwomen's shoes D.A.T.E. date 5,5 () sneakers multicolor leather BX144-36 , Salomon XA Comp 7 CS WP Women's Grey/Blue/Lucite Running Shoe 10.5M , New Womens adidas F30 adiZero TRX FG Soccer Cleats MSRP $105Nike Pegasus 32 H2O Women's US 8.5 Flash Running Trainers 806577 500 Sneakers , Under Armour Women's Charged Stunner Training Shoes Black 6Reebok CLASSICS WOMENS Furylite Olympic White Black AQ9859 FUTURE COLLAB Sz 7.5 , Skechers Sketchers Shape Ups Sneakers Shoes Women's 10, Gray with Pink , New Balance Minimus 80 V1 Womens Trail Runnnig Shoes Size 8.5 Goretex Grey RedASICS Weldon X - Grey - Womens , Funtasma Women's Gypsy 03ASICS Womens Gel Fortius TR 2 Training Shoe- Pick SZ/Color. ,
"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."