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.DUNHAM GREENLAND Brown LEATHER OXFORD SHOES WOMEN SIZE 6 med NEWJ Crew Nude & Sparkle Flats size 9.5 New Condition , gloria-33 Fashion Comfort Ballet Slip On Casual Office Women's Flats Shoes BlueGold Beige Sequin Beaded Slip On Shoes , DANSKO Poland Stonewash Denim Zebra Artisan Clogs 40 - US 9.5 , Women Cute trendy black shoes Size 7 , New Women Fashion Beach Summer Flat Shoes Casual Ladies Flip-flops Sandals , A New Day Womens Shoes Loafers Vegan Casual Size 10 BlackFranco Sarto Women's Shoes Brown Slip On Loafer Studded Jewelled Size 7.5MCorso Como Women's Black Leather Suede Flats 6 M , Enzo Angiolini LIBERTY ~ Metallic Silver Pewter Loafers Shoes ~ Size 7 N , New Vionic Romi Casual Slip On Loafers Midnight Blue Velvet Womens 7.5 $130.Skechers Madison Ave-Urban Glitz Black/ White Womens Sneakers Size 8.5M , Women's SAS Orange and Royal Blue Flats Shoes 7.5 M , Melissa Mary Jane Pink/Black Shoes, Size US 5 , Mephisto Women's Sz 10 Runoff Airjet System Beige Mary Jane ShoesWomen Rainbow Colors Breathable Holes Sneakers Slip On Casual Shoes Sports , EUC PUMA Fashion Sneakers Brown Pink Synthetic Women's Shoes Size 8.5 MediumSanuk Men's HALF DOME SUEDE SIZE US 9 M Slippers Slide On Scuffs Shoes SMF10884L , New! Women's Skechers 48903 Relaxed Fit Sassies Slip-On Oxford - Black/Blue N60Women's Qupid Women's Spyrock-05 Sneaker Inexpensive Athletic Shoes , Skechers GoWalk Lite Coral 3 Eye Boat Deck Women Trainers in Beige & Blue 15430 , NIKE WOMEN'S AIR HUARACHE RUN ULTRA SPORT FUCHSIA RUN TRAIN 819151 602 SIZE 5Women's Rockport TRUSTRIDE DERBY TRAINER BX2301 COMFORT ATHLETIC SHOES CHOOSE/SZ , NEW NIKE ZOOM RIVAL D8 D 8 Track & Field Racing WOMENS 8.5 Pink Laser Orange , Newton Boco Sol Blue/Pink Running Shoes Women's US 5.5 (K3,13)ASICS Women's Jolt Running Shoes Glacier Grey/Aqua Splash/White Size 7.5 , Nike Roshe One Flight Weight GS Rosherun Sprite Blue Green Kid Youth 705485-404 , Converse Shoes Chuck Taylor Ox All Star Baby Pink Sneakers Womens 4 , New Womens Simple Brand 50's Lovers Lane Natural Sneaker Shoe US 7 ,
"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."