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.Minnetonka Moccasins Storm Blue Size 8.5 With Beaded Bird UC 7 47647 20983 9Sperry Top-Sider SHOES WOMENS SIZE 6 M , Ballerines SAN MARINA taille 36 NEUVES - NEW , Womens Born W9790 Bicycle Toe Fashion Driving Walking Sneaker Oxfords US 8.5 , White Mountain Women's Black Gypsy Cap Toe Buckle Flats Shoes Size 6.5 MSteve Madden womens shoes size 8 Whilma Style New , ELLIE Shoes Ballet Flat Bow Womens Glitter 016-MILA-G Red , Circus Sam Edelman shoes flats espadrilles slip on Wm 8.5 blue Extra Fries LeniAvia Fashion Sneakers Women's Size US 8 Free Computer Fix With Purchase , PAUL GREEN Suede Leather Low Wedge Ballet Flats Sz. 8 , US 10Women Bowknots Pointy Toe Loafers Flats Shinning Sequins Casual Comfortable ShoeRetro Womens Tassels Leather Casual Slip On Flats Mules Shoes Square Toe OxfordsSoludos Barca Striped Espadrilles, Gray/White, 37Skechers Memory Foam Mary Jane Shoes Sz 8 Multi Color Black Womens Comfy , Aldo Womens SIZE 9 High Top Fashion Sneaker Brown Gold Faux Leather Shoe , New Balance Women’s Vazee 2090 Size 7Asics Tiger Women Gel-Lyte V black black H661L-9090Fila STORM-W Womens Storm Running Shoe- Choose SZ/Color.Salomon X-Mission 3 Women's Teal Blue/Green/Purple Trail Runner 7MASICS GEL-Exalt 4 Grey - Womens - Size 10 BSkechers Go Walk 4 Select Womens Slip On Walking Sneakers Black/Gray 9 , New Paperplanes Women's K- Max Sports Air Running Athletic Shoes(P1101) Pinkconverse ct 70 hi 146972c size 9 Free shipping , Skechers Women's Synergy Sparkle & Shine Slip On Walking Shoes - Assorted SizesVibram Five Fingers Womens 8 / 39 W345 Bikila Gray Green Barefoot Running P6k , Nike Roshe One Moire Women's Athletic Shoe 819961 661 Size 11 , NEW Adidas Women's Supernova Sequence 9 Gray Running Shoes AQ3552Born Women's 'Cymbal' Light Grey Suede Low Top Fashion Sneakers Size 8Katy Perry Womens the heart sneaker Leather Low Top Slip On, White, Size 8.5 jDODVS Shoe Company Brown Suede Juliette Lewis Punk Rock Skate Surf Sneaker 8.5
"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."