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.Jessica Simpson Size 4 Ballet Flats Brown LeatherReef Brown Canvas Loafers Deck Shoes Deckhand Size 7 , Born Women's Black Mary Janes Shoes Size 7 1/2 , Drew Women Creme White Leather Orthopedic Comfort Mary Jane Shoes size 7.5 WWPrivo By Clark’s Brown Women’s Shoes Sz 9.5Steve Madden Ballet Flats Size 7 Gold Quilted Shoes Slip-on SlidesNaturalizer Response Casual Shoes Women's Size 8, BlackFinn Comfort $245 Patent Crocodile Print Leather Clogs Shoes Womens Size 9.5 MSalvatore Ferragamo Sport Womens Textile Mules Slip On Shoes Sz 6.5 BNEW! Roxy Women's Mavericks Shoes Black/White 425Q pzKeds Shoes Size 8 Womans Canvas Sneakers Fashion Casual American Flag PatrioticWOMEN BLOWFISH MALIBU WASHED CANVAS SNEAKERS MID TOP BLUE SIZE 8 M PRE-OWNED VGCNIKE Satire PRM Pink Black Zebra Shoes Casual Women Size 8.5 599140-661Ladies Canvas Trainers Shoes Casual Shoes Size 40 White New , Stuart Weitzman - RED Suede loafers w/ jeweled front detail - Size 6 / SpainMens Fleece Lined Knitted Mule SlipperASICS Gel-Craze TR 4 Sneaker - Women's Size 6 Gray/Mint , Women's Nike Womens Metcon Shoes 8.5 Reliable Quality Athletic ShoesWomen's Lamo Mens Chocolate Tremont Moc Discount FlatsWomen's sperry shoes size 12 womens New Products FlatsSkechers 34338 Gray Women's BOBS Size 8.5 Bliss 2.0 Restart Flats Casual BootiesCONVERSE All Star HI Parchment PrintedNIKE WMNS PRESTO FLY (910569 300) SZ: WMNS 6.5 RETAIL: $100.00New Women's Nike Free RN Distance 2 Running Shoes Size 6 SKU 863776-001Pureboost X Women’s Running Shoes New Size 9 Black , ASICS Womens Gel - Challenger 11 White Running Shoes Size 8.5 (357239)Adidas Stellasport Irana Women's Shoes Blue B25114, Size: 41 1/3 , adidas Women's NEO Courtset SneakerSkechers Taupe Multi-Knit Slip-On Bungee Sneakers - Visions 9W Sale , Rocket Dog Women's Reagle Dash Nylon/Moonwalk Pu Fashion, Black, Size 6.5 ,
"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."