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.Womens Size 6.5M Rockport Purple Suede Mary Jane Shoes Made in Brazil , Sofft Womens Brown Leather Slip On Mules Casual Comfort Flats Size 8.5 , Flossy Riorgordo Women's Khaki Grey Pull On Twin Gusset Leather Loafers NewGRASSHOPPERS ORTHOLITE WOMEN TASSEL LOAFERS M NAVY BLUE FABRIC. , Women's SAS Traveler Shoes Sneakers Size 10N Black Leather Tripad Comfort AA14 , NEW Sperry Top Sider Women US SIZE 5 Black Loafer , CROC BUSY DAY 2.0 HEATHER A LINE~DUET FLAT LOAFER SLIP ON SHOE~Gray~W 7~NWT , Ecco ECCO Womens Flat- Pick SZ/Color.Steven By Steve Madden Womens Aidan Slip On Loafer Shoes, Taupe Suede, US 7Klogs Piper Womens Clogs Display Model Shoes Black 11 MDisney Vans Villains Women's Size US 7///CM23.5MIZUNO VS-1 WOMENS SIZE 10 WHITE TRIMMED GRAY AND GREENSkechers Womens - Pink Walking Shoes Size 8.5 (326280) , Mens Slipper Shoes Mule Natural Leather Hand Made BrownNEW in Box YOUTH NIKE DUAL FUSION RUN 2 PINK LIME flyknit lunar free air max run~NIKE TANJUN Women's Shoes~SIZE 8.5 M~Black / Metallic Red Bronze~NEW IN BOX~Women's reebok training sneakers size 9 Wear-resisting Athletic ShoesWomen's MERONA SHOES WOMEN'S SIZE 9 Moderate Price Flats , 844673 003 "NEW" - NIKE ZOOM SPAN CROSS GYM TRAINING RUNNINGASICS Women's Gel-Fit Tempo 3 Cross-Trainer Shoe - Choose SZ/Color , Nike Women's Roshe Two Flyknit V2 Running Shoes Grey Trainers 917688-002 Size 9 , adidas Originals Womens Gazelle Casual Shoe White/Metallic Gold BA9596Reebok CL LTHR Leather Triple Black Vintage Women Running Sneakers Shoes R003912Adidas Women’s Superskate Slip W Olive Sz 8 NIB 467733 , adidas Originals BB2344 Womens Eqt Racing 91 W Fashion Sneaker , Vizsla Dog Blue White Print Sneakers For Women-Free ShippingNike Air Huarache Run Ultra Women's (Size 7.5) Blue / White 819151 403Ladies Shoes New Leather Fashion Wedge Sneakers Sport Wedge Ankle Boots Oxfords , Mizuno Wave Inspire 11 Running Shoe - Women's Size 8.5 - Green , Salomon X Ultra Low II Women's Peacock Blue/Deep Blue Hiking Shoe 8M
"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."