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.Anne Klein Blue Ombre Akprogresiv Twill Espadrille Flats Sz 9.5 Never Worn!Rockport Womens 7.5W Sneakers/walking Shoes Tan/salmon Super Comfort Wore 1XMushrooms Women’s Sz 6 Tan Leather Comfort Shoes Flats Beige New Loafers , NATURALIZER "SURREY" DARK BROWN LEATHER SLIP ON COMFORT SHOES Size 6 1/2 M , Cole Haan Cream/Taupe Leather Flats, Woman's 8B , Bella Vita Switch II Slip-On Sneaker - Women's Size 9.5W - Blush , Women's Maria Sharapova by Cole Haan Ballet Flats Shoes Sz 5.5B Black Leather B3 , Womens Dansko Solstice Clog Shoe Loafer Brown Leather US 6.5 to 7 , Adidas Adiprene running Shoes Women’s Size 7 PinkWomen’s Outdoor Running Sports Shoes Travel Athletic Casual Walking Sneakerswomens casual sport board shoes high cotton-padded autumn winter warm new , Handmade Elephant Rope Women's Sandals - Sizes 4-10 US WMERRELL women's Jungle Moc Gunsmoke shoes size 7.5 J60788 , Altra Zero Drop Athletic Running Shoe Sneakers Purple White Women's Size 10/42LL Bean Women's Canvas Sneakers Color Dark Orchid / White Size US 6M NewNike In Season Trainer Sneaker - Women's Size 8.5, White , Skechers GO Walk Joy Slip-on Shoes Radiant White 7M NEW A302183 , New! Womens Skechers 12789 Burst - City Scene Casual Sneaker Gray F24 , Women's Nike Max Air Women Low-priced Athletic ShoesAltra Women's One V3 Road Running Shoe, Light Blue/Coral, 8.5 B USSKECHERS USA Inc 709 Skechers Og 85 Low Flyers Womens Jogging- Choose SZ/Color.NIKE Air Max Sequent 2 Women's Running Shoes Multiple Sizes Gray 852465 007 , New Balance CW1600GM: NB 1600 Elite Edition Capsule Meteorite Collection Sneaker , NIKE Son Of Force Mid Womens Size 6.5 Rose Particle Blush Pink 616303-603CARLOS "SUTTON" Black Micro Studded Flat Slip On Sneaker Size 9.5 Super Cute!! , NIKE ROSHE ONE WINTER Tennis Shoes Womens 9 Red Casual Walking NWOB , Merrell J35516 Siren Edge Athletic Shoes - Women's Size 9.5, Grey , Vans x Lazy Oaf Classic Slip-On Checkerboard NEW! RRP$120 Womens US5.5-9.5 , Nike Women's Dunk Low Shoes White Pure Platinum Gum 311369-100 Size 10 NWOBAsics Women's Gel-Cumulus 18 Indigo/Silver/Pink Glow Running Shoes 10M
"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."