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.American Living Donica Braided Rope Toe Tie Ballet Flats, Black, 7 US Display , DANSKO Womens Vegan White Tan Mary Jane Comfort Clogs Size 40 9.5-10BORN Womens Size 3 Brown Leather Slip On Loafer Flats Shoes Euro 34 Small Shoe , New Hush Puppies Prescott Women's Loafers Slip On Brown Leather Men's 11 W NWOBBorn BOC Womens Shoes size 6 M Black Leather Flats Comfort Slip On Shoes , Jambu Women's Sideline Encore Water Shoes Baby Blue Size 9BOC BORN Peggy Black Quilted mult-co Clog Mule Loafer Shoe Womens 8M Rare!Womens "Talbots" Leather Canvas Textured Gray Animal Print Flats Shoes Size 6M , Lucky Brand Size 8 M LP- Erin Black Ballet Round Toe Flats NIB Monte LeatherARA Shoes Women's Shoes Shoes Touch Fastener Purple Air Cushion Size 4 1/2 , Birkenstock Shoes Womens Sz 38 US 7 Navy Blue Suede Slides Buckle ExcellentMontana Size 6 M ROSALINDA Gray Leather Mary Janes Loafers New Womens Shoes , Women's Dansko Shoes, Multi-color, Canvas, Striped, Boho Hippie, 37/7PUMA Women's Evader XT Geo, Blue Coral/Clearwater, Training Shoes, 7MAnn Taylor Camryn Hcalf Bow Flat 6 BNIBFlat Nine West SpeakUp Flat Red/White Mid Gingham Shantung , Adidas Adiprene Running Shoes Women Size 10 , Saucony Womens Liteform Feel Sneaker Black White Size 5 M USSilver Womens Size 8 Keds Champion Oxford Canvas Sneaker Shoes , NIB Converse Pro Leather Perforated Suede Low Top Sz 8 - $85 , Nike 624976 Womens Speedlax 4 LE Lacrosse LAX Soccer Low Top Cleats Shoes , WOMENS GEL QUICK WALK SHOES ASICS Q268N black purple Size 11.5 workout run Q7 , Women's Comfort View Sandals Size 7WW Fashionable Athletic Shoes14 New Rare Adidas Originals - Superstar Women's Shoes SZ 7.5 Silver BB8139 , Women's Vans Old Skool Cup Leather Aqua Sea VN0A2Z5VJY8 Brand New , Womens Vintage 1990's Keds Shoes Hot Purple Black Size 7.5 , Puma Axel Ballet Slip On Ballerina ShoeS 6.5 Gray Purple BRAND NEW IN BOX , NEW BALANCE 621 ALL TERRAIN US WOMEN 8.5 B PRE-OWNED WT621GP , Merrell 10412 Sonora Ventilator Taupe Trail Hiking Driving Sneakers Women's US 8 , Womens Altra Size 7 A2233-2 110 Zero Drop Fushia/Dark Gray Intuition 1.5 Shoes
"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."