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.LIFESTRIDE Brown Loafers 1 1/4" Heel Womens Slip On Shoes Size 6M EUCSplendid Womens Jaime Tan Espadrille Casual Shoes 8.5 Medium (B,M) BHFO 3860Womens Soludos Blue Striped Espadrilles Slip On Size 39 LIKE NEWSAS Suntimer Sandals 6 M Tan Leather Open Toe Comfort Shoe Cushioned FootbedNWT SANUK SWF10656 Pick Pocket Tee Wo's 6 Gray White Stripe Slip OnsWomens Shoes Anne Klein Sport Ankondria Light Pink EUC Size 6.5 US , MARC FISHER JODITA Women Flats Size 9M Tan Black Leather , Women's Shoes 11W Loafers SAS Leather black comfort EXC! , NEW! Cole Haan-NikeAir- Women's Cream Gold Buckle Flats-Size 7.5B-Cute!Muk Luks Women's Size 8 Shoes Blue Flower Erin Sport Flats Sling Backs loaferWomens Born Woven Indian Blanket Woolen Top Clogs Mules Multi Color size 7 / 38 , NEW OH HEALTHY HEELS YELLOW GENUINE LEATHER COMFORT FLATS PADDED INSOLE 8.5MClarks Women’s Black Leather Buckle Fastener Mules Size 8 $85 , Women's Vera Wang LUNA Silver leather peep toe Flats Sz 7.5 MTraditional Ethnic Women Shoes Indian Handmade Khussa Pointy Flats Jutti US 5-8Gentle Souls by Kenneth Cole Gentle Souls Iso Block Wedge Sz:6.5 MEDMARCO TOZZI Ballerinas Slipper Shoes Pumps Black NEWSkechers Reggae Fest-Willows Black Blk Womens Flats Size 8M , Nike Women Shoes Size 10 Orange Sneakers Workout Free5 B70 , Easy Street Womens Barbara Low Top Slip On Fashion, White-floral, Size 10.0 uMWZNew Balance N2 1080V4 Women Size 8.5 Fantom Fit Athletic Running ShoeNike Air Zoom Pegasus 33 RF Jungle Pack Running Shoes 849812-406 Womens size 10New Balance WSRMCBW Cypher Run Shoe Black/White Colorway BNIB!Womens Adidas PureBoost Chill Running Trainers S79268 , Saucony Guide 10 Blue Women's Running Shoes Size US 6.5 (G2,17) , Women's UNDER ARMOUR THRILL 2 Gray+Pink Casual/Athletic Running Shoes NEWWomens Asics Gel Saga White H5P8L-0101 , Skechers Sport Women's Elite Synergy Fashion Sneaker , NEW Women Outdoor Running Jogging Purple Pink Shoes Mesh Leahter 2424 g_eadidas Performance Women's Irana 2 Cross-Trainer Shoe ,
"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."