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.02-3275 Sam Edelman Women's Carrin Raffia Espadrille Loafers Tan SZ 8.5WSkechers Go Walk 2 Womens 13590 Walking/Casual Shoes , Vionic Spark Kiska Round Toe Flats - Natural SnakeNEW Karl Lagerfeld Odetta Black Suede Floral Slip On Mule Slide Shoe Sz 6Cole Haan 9.5B Women Flats Shoes Tan & Cream LeatherSUSI RUIZ Shoes 169407 White 38 , Clarks Mary Marigold Casual Slip On Shoes - Women's Size 11 M - BlackNike In Season TR Women's Running Shoes Anthracite/Pink Flash/White Size 9.5(US)MERRELLS Shoes Slip On Women's Size 6.5 Blue Suede Walking Hiking Great TreadWomen's Sperry Songfish Waxy Canvas Taupe STS96656 Boat Deck Shoes , SKECHERS Womens size 9 GO WALK GO GO MAX MEMOARY FOAM ATHLETIC SHOES EUCDearfoams Men's Perforated SlipperNIKE Women's In-Season TR 6 Cross Training Shoe, US 9.5 / WhiteSpecialized sz 39 8M Tahoe gray cycling womens biking athletic shoesWOMENS ADIDAS "STAN SMITH" WHITE/GOLD SNEAKERS SZ 7Women's Asics Black,Pink, Blue Running Shoes Athletic Sneakers size 7.5Earth Origins Carly Black Suede & Mesh Slip on Sneaker6.5W NEW , New!?Women's Skechers Relaxed Fit- Bikers – Pedestrian 48930 Choc 118M pm , adidas Performance Womens Distancestar W Cross-Trainer Shoe- Pick SZ/Color. , Converse Chuck Taylor All Star Ox Womens Pink White Canvas TrainersZOOT ADVANTAGE WR 37-42.5 NEW triathlon trainer ultra race tempo kane kalaniAnthropologie Leather Sneaker Slides White Size 9.5 , ASICS Women's Cross Freak 2 Cross-Country running Shoe - Choose SZ/Color , Converse Women's Madison Leather Low Top Sneaker Black Size 5.0 DyJT , Converse Breakpoint OX Women's Casual Girl's Casual Retro Fashion Trainers White , New Sperry Sky Sail Metallic Sneakers Color: Rose Dust, size: 6.5M , Asics RoadHawk FF2 (Women's) Running. White/Blue Print , Mizuno Wave Paradox 3 Running Shoes-Women's sz 9.5 BlackNew Adidas Womens B39216 Blue Softball Cleats Size 12Brooks Glycerin 7 Women's Size 7.5 B Running Shoes Silver Athletic
"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."