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.BareTraps Mitsy Hidden Wedge Flats 551, Navy, 7.5 US , Bare Traps Womens jackeline Closed Toe Ankle Wrap Espadrille FlatsWeekends By Khombu PAYDAY Women's Black Peep Toe Mary Janes Size US 6Born Toby Shoes W31011 Pebbled Leather Slip-On Clogs Wedge Blask Size 6 , Hollywould Women’s Fuchsia Pink Flats Sz 7 Pom Shoes Italy , DANSKO 36 Black Nappa Leather OLIVIA Slip On Comfort Loafers FlatsFree People Womens Solstice Espadrille Mules Slip Ons Multi Fabric Size 37 NewCroc's Women's Citilane Roka Metallic Slip 205154-0P1 in Silver Sz 6-10 NEW , BASS: Vtg Made In USA Ox Blood Burgundy Leather Tassel Slip-on Loafer Shoes, 7 D02-3410 Hush Puppies Chaste Ballet (Azure Blue Suede) Women's Flat SZ 9.5 EWRyka Tan Purple White Adjustable T-Strap Walking Comfort Woman's Shoes Size 9Karl Lagerfeld Women's Tilda 2 Black Silver Metallic Loafers Flats Sz 7 New $120 , Clarks Keesha Luca Loafers, Women's Size 9 M, BlackDREAM PAIRS Kid's Water Shoes Athletic Lightweight Walking Shoes Sneakers , Ladies Get Fit Mesh Go Running Walking Lightweight Fitness Trainers All SizesAsics Gel-Kayano 22 Womens US Size 9.5 US Running Shoes Teal Silver T597QMERRELL Wo's 6 Eu 36 Ash Blue Heaven Athletic Hiking Trail Shoe Sneaker J257452C , Womens Columbia Sawtooth Trail Hiking Shoes Gray/Blue USA Sz 6, EUCAdidas AW4323 Sz 8 US Women's Cloudform Advantage Clean White Leather SneakersRalph Lauren Polo Sneakers Orange Canvas Plaid Sports Fashion Womens Size 8.5New Balance 574 Running Shoes Womens Size 9B , Women's BareTraps Women's Kami Flat Durable Service FlatsSpeedo Women's The Wake Athletic Water Shoe Grey/Neon Pink 7 C/D US , Superga Women's 2311 Quilted White Fashion Sneaker Size US 8.5Adidas womens SNOVA seq 5W shoes new Q23652 sneakers , NIKE WOMENS AIR FORCE 1 PREMIUM URBAN HAZE GREEN BLUE WMNS SZ 6-12 315186-341 , Puma x Fenty by Rihanna The Trainer High White - Womens - Size 9 B , NEW | Nike | Womens | In Season 7 Cross Training Shoes | Black | Size 6DC Women's Evan HI TX LE Skate Shoe , ALTRA WOMENS PROVISIONESS RUNNING SHOES,A22341,CHARCOAL/MAGENTA US SZ 5.5, ,
"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."