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.Naturalizer Remember Camel Nubuck Leather Flats , Size 8.5 M , Womans Montana Artisan Crafted Black Leather Flats Round Toe Comfortable Size 8MNaot Womens Heels Loafers Black Color Size 36MERRELL Womens Black Encore Breeze Slip On Mule Flats Fabric Ortholite Size 6Butterfly Twists Holly Cream Black Womens Ballerinas Flats ShoesLolita Women’s Bow Knot Flat Heel Round Toe Princess Girls Shoes Cross StrappyLiz Claiborne Pointy Toe Short Heel Sz 7.5 Maroon Croc Print Bow Front Flats-587 , $140 SAM EDELMAN FAIRLEIGH Saddle Orange Spice Leather Designer Flats 6 , Ecco Brown Mary Jane Bison Floral Strap Clogs Flower Size 40 Eur 9 9.5 US , L Orchid Ladies Flat Heels Loafers Rivet Decor Slip on Shoes Court Grace SandalsEasy Street Women's Lovey Flat, Navy Suede Leather/Black Gore, 12 M USNew AUSTRALIA LUXE Collective Grace Vibram Smoking Suede Flats 8Zoot Sports Solana - Pink - Womens , Crocs Lm-01 White Rubber For Men Brand ManthanMen's Sandals Flip Flop AIR Slip On Sport Slide Adjustable Strap Shower SlippersMBT Chakula GTX 400302-03 GORE-TEX Orthotic Toning Shoes Womens 39 8 - 8.5Women's SKECHERS GOWALK 14137 GRAY Athletic/Casual Sneakers Shoes NEWWomen's Mizuno Wave Enigma 5 Running Shoes Sz 11 US , WMNS NIKE AIR MAX THEA GAME ROYAL BLUE-PINK GLOW-WHITE SZ 7 [599409-403] , Nike Zoom Live II White/Pure Platinum/Gum Light AH7578 Women's Shoes Size 7 , Women's Adidas Terrex AX2R - Grey - Width: med - OutdoorBearpaw Women's Layla Caged Sandal Grey Synthetic Strappy SandalsNike Wild Trail Women's Shoes 643074-001 NIB Authentic US 6 -ASICS Womens T6d6n Aquarium/FlashCoral/BlueJewel Running Shoes Size 10 (362323)Brooks Ghost 9 11M / 43 EU Black Teal Purple Athletic Shoesadidas EQT SUPPORT RF - Red - WomensCalvin Klein Womens Vespera Low Top Buckle Fashion SneakersBernie Mev Womens Rigged Connect Low Top Slip On Walking Shoes Jeans Size 6.5Adidas Womens Baseline White/Black/White Fashion Shoes Size 8.5 (420540)Marc Fisher Calie Brown Leopard Slip On Fashion Sneaker Shoe NEW ,
"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."