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.Womens Ladies Girls Black Faux Suede Bow Studded Ballet Flats (NIB)Ana Size9 New Ballet style square toe flats burgundy suede w/ankle straps B1Rieker Sportlich Long Wing-Tip Women's Brown Leather Oxfords Shoe Size 6 (DA4)Lucky Brand Womens Sesame Persian Leopard Brown Leather Flats Shoes Ret $90 NewWomen's 6 M Cole Haan Country Brown Leather Loafer Slip On Moccasin Shoes SlideMisses' Size 9.5 Grey/Black Leather Wedge Shoes - Dana Buchman NIB! , Klogs Clara Women's Leather Clog Display Model Shoes Mustang 6 M , Jambu Women's BAILEY MJ Mary Jane Flat , NEW Clarks Artisan Nubuck Leather Slip-On Shoes DAELYN HILL MUSHROOM 11W WIDEDrew Rose P221 Black Mary Janes Orthopedic Therapeutic Comfort Shoes Size 7.5WPropét Womens Cameo Leather Closed Toe Ballet Flats Chocolate/Bronze Size 8.0**NEW** Gola Women`s Sneaker '' Runner'' , Womens Champion Sneakers Mary Jane Style Gray light pink Size 6.5 , Women's Flat Platform Nurse Shoes Casual Walking Shoes Women Sneakers White 41(36) FORNARINA Brown Heeled High Boots Tassle Leather , NEW Womens KENNETH COLE Slip On Gold Keena Loafer Shoes Size 7.5GUESS Womens Jaali Fabric Cap Toe, Gold, Size 7.5 vlNTWomens Mens Unisex Natural Virgin Wool Felt Sheep's Wool Lining SlippersWOMENS MBT DARK BROWN AND ORANGE SIZE 10 , NEW BALANCE 1110 Grey Teal Trail Running Sneakers Womens US 8.5Giro Xen 22042W Cycling Shoes Size 10 Running Hiking Biking Mountain Road TrailSkechers Womens Wavelite - Choose SZ/ColorASOLO DIGITAL SUEDE GORE-TEX HIKING TRAIL SHOES WOMEN'S 7 M RTL $160 , Puma Suede Classic X Irides Women's ShoesNike 'In Season TR' Training Shoes Sz 11 , NIKE LunarTempo 2 Print Womens Sz 6.5 Shoes Violet Crimson 831419 500Vionic Ailie Mary Jane Sneaker Shoes Size 9 Needs Insoles White Gray & Pink , New DC SHOES ADJS300043 TONIKW Women's Deep Teal(DTL) Sneakers US Size 6~10PRINCE T22 WomensTennis Shoes Sneaker White & Blue Running Trail Size 8 , New Balance MD500 Silent Hunter Track and Field Spikes Women 9 new FREE SHIP ,
"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."