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.New Women Qupid Bee-22X Leatherette Round Toe Bow Tie Ballet FlatDr. Marten's women's comfort mary jane buckled, double split toe loafers 7 MWomens B O C Born Concepts Slip On floral Shoes Size 10 M white Brown Yellow , CROCS Rubber Rain Rubber Clog GARDENING WATER SLIP ONS Sz MEN 4 WOMENS 6 SHOES ❤ , Skechers BOBS Women's Plush Lite-Engineered Knit Ballet Flat Gray 8 M US , Klogs Cardon Women's Leather Clogs Display Model Shoes Black Wigwam 6.5 MTopshop Tan Leather Flat Sandals SIZE UK5 EUR38 US8 , Alegria By PG Lite Black Leather Mary Jane Shoes PAL-601 Womens Size 8.5 M EU39 , “LL Bean” Hiking Trail?-Water Resistant Walking Sneakers - Size 7 MByron Bay Co Shaba Flat Loafer , Trina Turk Women's Ballet Flat Shoes, Size 6 1/2, Tan, Beige, Taupe, Curved, EUCMerrell Chameleon ARC Wind GTX Pewter Hiking Walking Trail Shoes Women's US 7 B5 , Delta Womens Flats Low Heels Buckle Trainers Ladies Shoes Pumps Plimsolls Size , WMNS NIKE ROSHE ONE JCRD PRINT$60 Steve Madden Womens Nyrie Flat Slip On Shoe, Purple Multi, US 9 , Saucony Ride 9 Womens Size 8 Cleaned Run Walk ShoesWomen's Dollhouse Womens Flats Quality Product FlatsWomen's Espadrilles "Priced To Sell!" Easy-to-clean Surface Flats$200 size 40 US 9 Ash Impuls Black Genuine Leather Sneakers Slip On Womens shoesNike Dart 10 X Running Cross Training Workout Blue Mesh Sneakers Shoes Womens 8 , Nike Women's Downshifter 6 White Blue Silver Running Shoes Size 7 , Skechers Women's Relaxed Fit Breathe-Easy Allure Black Sneakers ShoesSKECHERS Women's ON THE GO CITY POSH FASHION SNEAKERS SZ 6 GRAY SUEDE LEATHERAlegria KENDRA SANDAL WOMENS SHOE SIZE (40) 9 - 9.5 GOLD KEN-680W NEW , KEEN Womens - Brown Trail / Hiking Shoes Size 11 (356430)SKECHERS Flex Appeal 2.0 Sneaker - Women's Size 7 Black , Asics Gel Nimbus 15 Womens Running Shoes sz 6 Pink Purple Silver IGS SneakersSkechers Women's On The Go City 3.0 Immerse Charcoal 14759/CHAR , Nike Kaishi 2 Print Running Shoes, Women's Size 10, Ivory/BlackNEW Womens NIKE Rival MD Hot Pink Track Running Spikes Shoe 5.5M - Buy!
"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."