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.NEW! Avon Women's Pamela Loafer Brown 426JK dz , EUC! COLE HAAN WOMENS SLIP ON LOAFERS CLOGS SHOES BROWN 7.5MVintage Rajasthani Velvet Royal Women Mojari Jutti Belly Shoes Khussa us-7 , Lands' End Womens Red Leather Suede Casual Shoes Slip-On Loafers Size 6M WOW!!!! , HUSH PUPPIES Camden Green Suede Leather Loafer Mocs Women's ~ Size 6.5 ~ NEW! , Earth Spirit Sz 10W- Eur 42 Black Loafers Princeton Slip Ons Buckle Gelron 2000Sam Edelman Dominique Purple Leather Snakeskin Flats Pumps Shoes Sz 8M , SAM EDELMAN FELICIA FABRIC PALM LEATHER TRIM BALLET FLATS SHOES WOMEN'S 6 M , Womens Bohemia Moccasins Mid Calf Flat Shoes Fringe Tassel Suede Snowboots SizeNew Zara Slides Interchangeable Ribbons Leather Sold Out black Size 37 (6.5 US) , Women’s Clarks Black Leather Slip-On Shoes Clogs Mules US 8 M Brazil 35961 , Skechers Women's Vaso-Mitad-Perfed Twin-Gore Open-Back with Brown Size 8.5 , Steven Natural Comfort Lora Embroidered Sneaker Mule GRAY PEACOCK 9WNIKE GOLF BELLA LAST Women Golf Shoes Size 7 White Leather Soft Spikes , New Balance Women's 555 Shoes Black , Barbie Shoes Mattel Sneakers Size 6 Women’s Shoes NWOT Fast Ship KicksDr. Scholl's Womens Abbot Black Suede/Leather Fashion Sneaker Size 6 (31830) , NIKE ZOOM PEGASUS 29 SHOES ATHLETIC TEAL AND PINK SIZE 7.5 MESH SNEAKERSWomen's Nike shoxs women Serviceable Athletic Shoes , Women's Phat Farm shoes A Complete Range Of Specifications Athletic ShoesDKNY Womens Bobbi Leather Metallic Slip On Fashion Sneakers Shoes BHFO 6873POLO RALPH LAUREN NEW BALANCE 696 WOMEN'S US OPEN TENNIS SNEAKERS SIZE 8.5 , New Balance Women's W860SB5 Running Shoe New in the Box , Rag & Bone white Standard Issue canvas sneakers Eu: 39.5 Retail $195Bordello Women's Teeze 02ASICS TRAINING GEL-FIT NOVA WOMEN SIZE 7 PINK SNEAKERS, NWOBNWOB Women's Reebok White/Navy Roadwalker DMX Size 9 (1999)Nike Sneaker Hoodie Boots Womens Sz 11 Taupe/Brown Fur Lined Zip Ups Casual , Katy Perry Womens The Lena White Fashion Sneakers 9.5 Medium (B,M) BHFO 9256 , Asics Womens Size 8 Gel Venture 6 Athletic Running Shoes Black Carbon Neon Lime
"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."