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.NIB Merrell Mimix Romp Leather Cut-out Slip On Shoe Dark Brown Womens Sz 6-7.5Sofft Wedge Sandals Shoes Women's Size 7.5 N Brown Leather Open Toed Classic , Alfani Womens Gessey Closed Toe Slide Flats , EUC CLARKS BUCKLE WOMEN SZ 8 M BROWN SLIDE CASUAL MULE CLOGS SHOES BUCKLEPlay Hookie Blu Kicks Women 8.5 Blue Pink Stripe Fish Slip On Loafer Canvas Shoe , Clarks Privo Women’s Shoes Slip On Beige Suede Walking Active Outdoor Sz 8M , DR. SCHOLL'S WOMEN'S WYNN CASUAL LOAFERS CORAL FABRIC US SIZE 7.5 MEDIUM (B, M)WOMENS MBT KAYA CHOCOLATE BROWN SUEDE MARY JANE WALKING COMFORT SHOE , NEW Goby Cupcake Printed Flat, Women Size 6, $99 , LifeStride Women's Vanity Slip-On Loafer Mushroom Size 8.5 , NEW YORK & COMPANY Ballet Flats Pink BRAND NEW Two Tone Flats Womens Shoes Sz 6WMNS NIKE AIR MAX THEA MINERAL TEAL-VOLT-WHITE <599409 301> ATHLETIC , DC Women's Council Mid TX Mint High Top Skate Shoes 8.5MBrooks Glycerin 13 Black/ Purple Training Running Tennis Shoes Womens Size 8.5 , Qupid Women's Narnia-01 Fashion Sneaker, Grey, Size 5.5 , Puma Eskiva Mid Remaster - White - WomensWomen's Women's Sperry, Koifish Boat Shoe Bargain Price Athletic Shoes , Men's Shoes Slippers Glerups Boot Slipper Red 40.0 Exquisite Workmanship SlippersWMNS New Balance Women's 696 WL696NTC Tan Sparkle Classic Runneradidas Women's Cf Lite Racer Cc W - Choose SZ/Color , Nike Rosherun Slip Women's Shoes Size 10Vans Blocked Classic White Black Old Skool DX Shoes , NEW! Nike Women's Free TR Focus Flyknit Shoes Black/Gray J azVionic Elation 1 Athletic Shoes - Women's Size 7.5, Grey/Coral , Women’s adidas Originals Tubular Invader Strap Shoes Size 8.5 White Beige , Nike Flex RN 2017 Running Shoe - Women's Size 7, BlackSaucony Women's Ride 8 Silver/Purple/Blue Road Running Shoes 6.5M , New Balance Vazee Transform Women's Training Shoe Sneaker Grey US11 (EUR43) , Womens Asics GT II Dark Blue Magenta H593Y-5128 , Skechers Sport 12404 Women's Heart To Heart Fashion Sneaker, Grey Mint ,
"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."