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.Franco Sarto Black Patent Leather Womens Loafer Size 7 1/2W 2 Inch Heel , Marc Fisher Womens Renae White Casual Shoes Sneakers 10 Medium (B,M) BHFO 1539 , Trotters brown leather shoes, slip on, size 9 , 112 Vince Bray Shell Velvet Slip On Flat Loafers Women's Sz 5.5 MNatural Soul Vivian Casual Shoes - Women's Size 7.5M, BlackSeven Dials Devi Lug Sole Oxfords, Silver/Metallic, 7.5 USNot Rated Waati Slip-On - Women's 7.5 M, Taupe , KLOGS CAMILA WOMEN'S LEATHER CLOG SHOES DISPLAY MODEL TEX MEX 7.5 M , Topshop Nude Leather Flat Sandals SIZENike Downshifter 5 Running Shoes, Grey/Purple, Womens US 8 , J.Crew Emma Bow Ballet Flats Sz.6.5 In Sunbaked Orange , Women's Retro Nike Shoes- Silver And Red - 316587-061 Size 8Vibram Five Finger Barefoot Running Shoes SNW3664 Blue/Yellow Women Sz 36 (CF7)Fila Big-Kids FACTION 3 Sz.5 Athletic Med .Yellow/Black/White RM00179-703 , New!?Women's SKECHERS RELAXED FIT - ALLURE 22535 White Slip On Shoes 127Q pm , Asics Gel Venture 5 Athletic Shoes Women's Gray Green Pink Size 9 US FLAW , Bees By Beacon Laurie Women's Sneaker, Gray, Size 10.0 WuTRNike Lunarglide 9 904716-002 Womens Size 7 Grey Running Athletics Shoes IP-400 , Brooks Ghost 10 Womens Size 9NEW! Converse Classic All Star High Top Canvas Sneakers - Size: M7.5/W9.5 , Women's Jambu Women's Dory Ballet Flat Louis, Elaborate FlatsWomens Skechers 12214 SKECH AIR 2 PATHWAYS Memory Foam Athletic ShoesBeagle Pink White Print Running Shoes For Women-Free ShippingSperry Top-Sider 7 Seas Sport Womens Dusty Blue SneakersWomen's Casual Running Dress Trainers Ladies Sneakers White Fashion Sport Shoes , Skechers Women's You Walking Shoe - Choose SZ/ColorDemonia Women's Charade 28 , ECCO BIOM Grip Hydromax Gray Leather Athletic Shoes Women's Sz 42Mizuno Womens Finch Franchise G2 Softball Cleats Size 6 Black Pink NEWNew Balance Womens - FlintGray Running Shoes Size 8 (328078)
"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."