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.424 Fifth Womens Yeva1 Gold Metallic Slides Flats 10 Medium (B,M) BHFO 2871 , EUC Sperry Top-Sider Angelfish Boat Shoes Women's Size 6.5 M Loafers 9773581 , Dolce Vita Womens Black Shoes 7.5 , Clarks Collection Womens 6C Metallic Gold Loafers Fring Tie Accent Comfort EUCNew w/box Mix No 6 Danzey Women US SZ 7 Light Green Flats Teal Cute Comfort , Minnetonka Moccasin Women's Solid White Fringed Leather Kilted Loafers Size 9 , Corkys 9M Women's Ashley Elastic Slip-on Shoes in Multi Colors , Cole Haan Moc Toe Loafer - Leather Driving Shoes Brown Women's Size 6.5 BBorn Womens Size 8m US 39EU Brown Leather Mary Janes Loafers ShoesSkechers Madison Ave-City Muze Black/ White Womens Sneakers Size 6.5MBrand New MERRELL OAK Suede Leather Flats Shoes Brown Women's Size 6.5 Eu 37 , SAS loafers womens heel leather work career 10 S tripad moccasins , VGUC Etienne Aigner all leather 11 M womens loafer shoes brown Valentine work , Ladies Clarks Glove Puppet Black, Navy, Pink Or Ice Blue Leather Slip On PumpsSKECHERS WOMENS GO WALK 2 COMFORTABLE LIGHTWEIGHT CASUAL SHOES/SNEAKERS , NEW LADIES Ruched Almond Toe Half d-Orsay Flat. Size 6,6.5,7,7.5,8,8.5,9,10AIR WALK Sneakers Size 6.5 Black , WOMENS GENTLY WORN "NIKE" TRAINING FLEX TR2 GRAY & PURPLE WITH RED SWOOSH 6 1/2M , SKECHERS Women's "GOwalk 4" Charcoal Gray Slip-On Walking Shoes Size 7 , BareTraps Naxie Gray Mary Jane Active Mesh/Leather Flat Wedge Shoes, 7.5M - $79Natural Soul Women's Carryon Slip On Leather Loafers AB4 Brown Size 7.5M , Bloch Dance Women's Prolite II Leather Ballet Slipper White Size 4.0New Inov-8 Womens F - Lite 275 Red Running Shoes Size 10.5Womens Sperry Seacoast Navy Canvas Sneakers Size 6.5M (V945) , Men's Slippers Breathable Shoe Indoor Slipper Corduroy Short Plush Footwear New , WOMEN'S DARK BLUE KEDS SIZE 6 , YILAN Women's Fashion Sneakers Flexible Casual Sport Shoes Pink 7 B(M) US , Franco Sarto Pascha Slip On Sneakers 610, Red, 7.5 US / 37.5 EU , Nike Free RN 2017 Women's Running Shoes ( Size 8 )Blue White 880840 400 New $100 , RARE Baffin Womens' Cascade Slip On Size 9
"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."