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.THERESIA LADIES BROWN SUEDE LEATHER SHOES MADE IN GERMANY SZ 6 GREAT CONDITION , WOMEN’S SIZE 5.5 GRAY CORDUROY SPERRY’S TOP SIDER SHOES , Earth Origins Leather Slip-on Monk Strap Shoes Evelyn 7 medium blackMelissa Women’s 7 M Black White Jelly Shoes Ballet Flats Slip On , Talbots Size Shoes 7.5 Dress FlatsDonald J Pliner Women's Shoes Chelsea Boots 9 1/2 Medium Brown**Skechers Shiny Dancer Loafers, Women's Size 8, BlackNEW *KHOMBU* Womens Blue Leather/Plaid Canvas Loafer Slip On Boat Shoes, 6M , Dr. Scholl's Scout Slip-on Shoes - Women's Size 9 M - GrayKeds Women's Champion Crochet Fashion Sneaker Black Size 8.5Nike Womens Zoom Rival S7 Track Field Racing Running Sprint Shoes WITH Spikes 10SAUCONY KINVARA 6 YLO CYAN BLUE ORNG WOMENS 9 USED RUNNERS see pics-detailsGenuine British RAF Wet Weather Waterproof Breathable Over Trouser All Sizes NEW , Skechers Women's Go Step Lite-Persistence Sneaker , New Women Skechers Quick Escape White Size 7M Air Cooled Memory Foam , EXCELLENT! Asics GT-2000 T2K7N Running Shoes 8.5 Black/Blue/PinkNEW TWIN-SET SIMONA BARBIERI WOMENS SNEAKERSSkechers Street Furry Friend Pink Calf Hair Platform Sneakers Women 6.5 Punk NEW , Vans Classic Slip On (Suede Fleece) Khaki True White Skate Womens Size 9.5Skechers Variation Performance Womens Go Train City - Assert ShoeNew Balance Barringer 890 Sz 7 B Gray Green Running Shoes Worn 1x YGI E7 , STEVEN By Steve Madden Womens Neon Sneakers Shoes Creeper Silver Size 7.5Converse Womens Varvatos Chuck Taylor All Stars Size 8M Distressed Combat OliveAltra Womens Lone Peak 3.0 Neoshell Gray Zero Drop Trail Running Shoes Size 11 , PUMA Women's Basket Platform Reset Wn's Fashion Sneaker , Skechers Performance 14913 Womens Go 4- Walking Shoe- Choose SZ/Color.WMNS NIKE AIR MAX THEA 599409 307 , Women's Skechers On The Go City 3.0 Optimize - Black - Width: med - WalkingMunro Womens Cruise Low Top Pull On Fashion Sneakers , VANS SK8 HI REISSUE (DITSY BANDANA) CHILI PEPPER WOMEN'S SHOES ,
"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."