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.Lauren Ralph Lauren Abigale Brown Flats Shoes New/Display sz 5.5B , Cobb Hill Paulette Casual Shoes Women's Flats Black Leather 6 M $99Red Wing Women's Size 10B Brown Leather Loafers Comfort Work Wear Slip On ShoesEnzo Angiolini brown dark taupe loafers 10.5N womens leather shoes EalibertyMEPHISTO AIR RELAX LEATHER LOAFERS WOMEN SHOES US SIZE 6.5 MADE IN PORTUGALAnne Klein Zilya Elastic Espadrille Flats 726, White/White, 5.5 US , Miz Mooz Paloma Women 8.5 Red Leather Tapestry Fabric Slip On Ballet Flats ShoesARRAY Womens Freedom Leather Square Toe Loafers, White, Size 11.0 oKkU , NIB Sperry Top-Sider Maya Flat Platinum Gold/Silver Leather Womens Sz 7.5 8.5Lower East Side Loafers Rustic Brown Chunky Flats Shoe Slip On Womens Size 10MCIRCUS BY SAM EDELMAN Helen Women Flat Sandal (8.5M, BLACK)New!?Women's Skechers Relaxed Fit- Bikers – Pedestrian 48930 Black 129M pm , FILA Shadow Sprinter CoolMax Running Shoe | Womens 10 | purple | New in Box , KEEN Women's Versatrail Shoe, Blue, Size 5.0Nike air max womens size 8.5 pink and black , Skechers SHAPE UPS SRT Hot Pink & Black Toner Rocker Walking Shoes Womens 8.5 , Stella McCartney For Adidas Trainers US 9 UK7.5 Stylerunner $229 , Mens or Womens Leather Sneaker Shoe With Hook & Loop Closure-Wide WidthNew Balance Womens Wa365bk Black/White Walking Shoes Size 11 (421499)Ellie Women's Lady Jane-469 , Adidas Women's Questar Ride Running Shoes (DB1811) Athletic Sneakers TrainersNew Balance 996 Pink/White/Yellow Women's Summer Solution Shoes WR996CM Sz 6.5New Size 9 Fred Perry Laurel Meaden Black Leather Plimsolls - B2244WNew Keds 17ss Triple Metalic Canvas Sneakers Silver WF56557 Women Casual shoes , Nike Tanjun White Blue Women Size Running Shoes New In Box Original 812655 103ASICS GEL LYTE III SNEAKERS TENNIS SHOES WOMENS SIZE 7.5 B METALLIC GREENadidas Tubular Viral - Pink - Womens , NIKE DUNK HIGH WOMEN ALL WHITE K0200 8308319-112 size 6 , Vans Womens Authentic Sneakers Emerald True White Size 7 NewAdidas Originals Vigor 4 TR Womens Cross Training Shoe D74004 Sz 7 US
"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."