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.BareTraps Antaya Boat Shoe Size 5 1/2M Denim Blue Round Toe New NIB , Mark Jacobs Women's Purple Ballet Flats Size 3.5 , TORRID Whip Stitch Almond Toe Flats RED Faux suede 12w , Merrell Barrado Leather Sage Front Zip Casual Sneakers Women's Size 8.5 (DG3) , Sperry Top-Sider Dunefish Boat Shoes 147, Tan Multi, 9 US , CROC Women's Black super lightweight casual Slip-on Fabric Loafers flats size 8CLARKS EVERYDAY Sugar Sky Wo's 6.5W Brown Leather Mid Heel Pumps 84977Crocs Alice Black Mary Janes Womens Size 12 FlatWhite Mountain Finesse Comfort Flats 194, Black, 6 USWomen’s Pink flat sneakers with fur Pom Pom size 7Easy Spirit Womens Devitt Leather Closed Toe Oxfords, White, Size 7.0 XqgN , Born Womans Flats Size 8 39 M/W Brown Leather Buckle Mules , Women's 6.5 M Nancy Nancy Mary Jane Pink Leather Shoes Embossed Crocodile A78 , NIKE AIR FORCE ONE CUIR BLANCHES T 37,5 A ACH IMM FP RED MOND RELAY AFFAIRE , Naturalizer Womens Manor Fabric Closed Toe Slide Flats, Silver, Size 8.0 4OzgNike Revolution 2 Running Training Gym Shoes Pretty Colorful Sz 8 Eur 39 554900Merrell Select Grip Womens Azura Hiking Shoe 7.5 Castle Rock PurpleWOMEN’S PUMA IGNITE EVOKNIT LO RUNNING BLACK QUIET SIZE 11.5 Men’sPUMA PURPLE WOMEN'S FLEXRACER CELL RUNNING SNEAKERS ATHLETIC SHOES 181147 SZ 9 , WOMENS NIKE DUAL FUSION TR 2 PRINT SIZE 8 RUNNING WORK OUT SHOES 631661 101 CUTE , Spring Step Women's LucerneNIKE WMNS AIR MAX 90 Size 6.5 Metallic Mahogany Womens Running Shoe 896497-903ASICS Womens Gel-Flux 3 Running Shoes , American Eskimo With With Rose Print Running Shoe For Women-Free Shipping , New Balance 608v4 Womens Shoes White with Blue , Tonkinese Cat (Halloween) Print-Running Shoes For Women/Kids-Free ShippingNew Nike Womens Roshe One Run Running Shoes 844994-102 Sz 7 lt orewoodNike Benassi JDI Slide Women's White/White | Print 31261102Puma SUEDE CLASSIC - Fluorescent Yellow - Women’s 7.5Merrell Moab Beluga Ventilator Mesh Hiking Trail Shoes Sz 8 Continuum Vibram
"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."