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.Born 8 Black Mary Jane Flats Leather Comfort , GC Shoes Dianna Sparkle Ballet Flat Size 6.5 FuchsiaTROTTERS *JAMIE* BROWN LEATHER FAUX-PENNY LOAFERS - LADIES 7.5SCole haan women shoes size 9.5 black open toed , Gallorini Grey Leather High Heel Shoes (Eur 39 Au 8-8.5) Italian Designer , ArtEffects Footwear - Metallic Gold Leather and Clear Acrylic Stones - Size 8 , Steve Madden Women's Lynn Sneaker, Mauve, Size 7.5 sKdlVince Camuto VP-LUNNA Leopard Flats SZ 7 B Gray Brown Animal Print EUC , Dr. Doc Martens Air Cushion Sole Black Oxfords Sz US 4 M / 5 WomensClarks Unstructured Un Poem Womens 6.5 M Blue Leather Mary Janes Loafers ShoesEasy Spirit Shoes Comfort Womens Size 7Jessica Simpson Mikaela Round Toe Black Size 7.5MIsaac Mizrahi Mulberry Red Suede Pointed Toe Loafer Flats NEW MaggieNew Women`s Vionic with Orthaheel Technology Agile Hydra Shoes Slip-OnsTrotters Sante Ballet Flats-Women's size 5.5 M Grey , Merrell Chestnut Brown Suede Zip Athletic Walking Shoes Barrado Women's 9 / 40NIKE Womens LUNAR FOREVER 4 Black Charcoal Fuschia Sz 6.5 M WORN ONCE , Merrell Casual Shoes, Olive, Women's US Size 9 Narrow , Asics Gel Scram Trail Running Shoes Women's Size US 6.5 M Black T2J6Q , Keen Toyah Brown Nubuck Leather Hiking Trail Shoes Sneakers Women's Size 6/36 , Columbia Vulc N Vent Women US 8 Gray Sneakers EUC , Vans Off the Wall Womens Prairie Chukka Perfed Black Suede Shoes 8 RARE , NEW OPENING CEREMONY LEATHER GLOSSY OG CLASSIC SLIP-ON LX SNEAKERS - WHITE , MBT Women's Size 10.5 US 41 EU Black Kesho Nubuck Suede mary jane walking shoesNike Women's Flex Experience RN 5 Running Shoe , *BRAND NEW* Womens Adidas Court Stabil 12 Raquetball Shoes Size 8 Gold/WhiteNew!! Women's Skechers Sport Flex Appeal 2.0 Top Story Sneaker style YVintage 2004 Vans Classic two toned red/black classic white strip Women's 5.5NEW VINTAGE~ PRINCE sz 6.5 WOMENS TENNIS SHOES WHITE PURPLE TRIM IN BOX , MERRELL Women's Size 7 All Out Blaze Sieve Purple Hiking Trail Shoes ZU-631 ,
"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."