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.Sperry Top Sider Women's Chime Fuchsia Loafer 6.5M , LifeStrides Life Strides Brown Promise Mule Clog Slide Loafer Flat Shoe Size 8.5NEW! Merona Red 'Noele' Pointed-Toe Slip-on Flats NWT FAST SHIP! , Volatile Brown Black Mary Janes Loafers Croc Print Flats Shoes Size 7 @ cLOSeTCrocs Green White Purple Slip On Comfort Shoes Womens 8BOC Born Howell Tooled Leather Flat Slip On Shoes Dark Brown 9.5 Med C95222 , Rhinestone Flats size 7.5 - BCBG Loafers - BLING JEWEL Studded Pink Silver Gold , Keen Mary Jane Ankle Strap Pink Plaid Shoes Womens Size 7.5 Excellent Condition , Cole Haan Oxford Shoes Womens 7 B Original Wingtie Toe Tan Suede Blue , Jessica Simpson Womens Nalan2 Closed Toe Ballet Flats , Women's Converse Chuck Taylor All Star HI Top Shoes SZ 6 APPLE TEACHERS SneakersWomen's Square Toe Shinny Rhinestone Bowknot Flat Heels Fashion Casual Shoes SzNew Balance Women's Size 12 2E Wide WID627GF Navy SD ST Work Shoes ZS-1027 , Skechers Relaxed Fit Breathe Easy Faithful Slip-Ons-Women's size 6.5 Grey , Merrell Ventilator Moc II Casual Shoes, Olive, Women's US 7.5Women's Saucony Ride 7 Gore Tex running shoes sneakers size 9.5 , New Balance W860KM2 Running Shoes, Women's Size 10.5 B Pink , SilverConverse Woolrich Black Red black Size 6 Free shippingadidas Glc W - Purple - Womens , Women's Dressy red suede flats Genuine FlatsNEW BALANCE shoes 978 GORE-TEX HIKING BOOTS size 10.5 B j496 , Nike Dunk Low Premium Jetstream/Jetstream-Medium Grey-Dark Army 309730-001NIKE Hyperdiamond 2 Keystone 856434-018 WOLF GREY Size 11 , Womens New Balance Fresh Foam Running Shoes Gray White Gold Size 9.5 , NEW Women's Asics GEl-EXCITE 4 T6E9Q/9606 Shark/Coral/Purple Shoes Size 7 D WideNEW WOMENS SKECKERS SKECH-AIR,AIR COOLED MEMORY FOAM SNEAKERS GRAY/GREEN SZ 6.5NEW ROCKET DOG CABIN GRAY DOUBLE GORE SNEAKERS SHOES LOAFERS WOMENS 8 FREE SHIPNike Shox GO Running Sneaker teal White Silver Women 7.5 EUC , Demonia Women's Voltage 05 Ankle-Strap Pump , $250 SKECHERS Women BLACK CHILL FLEX MEMORY FOAM SLIP ON SNEAKERS SHOES 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."