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.British Style Oxfords Preppy Slip on Patent leather Loafers Block Heels Shoes , Cole Haan NikeAir Gold Ballet flats - Size 6 , Nautica PINK SHOES WOMEN'S SIZE 3ladies Sperry Top Siders Rubber Rain Shoes. Size 9M , Old Navy Blue Paisley Women's Textile slip On Ballet Flats 9M , Stud Shoes Zebra Faux Pelt White Navy Park Area Women size 3M NewCabela's Women's Sz 8.5 M Black Leather Slip On Clogs Mules Loafer Shoes , New Chinzia Soft Women's Grey Suede Platform Shoes Size 40US Italy $140.00 , Calvin Klein Jeans Ciela Moss Waxy Smooth Sage Pump Pointed Toe Flats New Box 7Skechers Womens Bikers -Fiesta Mary Jane Flat- Select SZ/Color. , Tory Burch Women's Purple Jelly Slip On Round Toe Ballet Flats Sz /US 5.5Isaac Mizrahi Saddle Brown Suede Pointed Toe Loafer Flats NEW Maggie , SUPERBES SANDALES CUIR PARABOOT T 37 VINTAGE COLLECTOR EN TTBE A ACH IMM FP , Rocket Dog Women's Chowchow Lucky Eyelet Cotton Sneaker, Black, Size 8.0Volatile Kicks Fashion Sneaker Red&Orange Size - 7,5 NWOB HYPE Comfy! , Reebok Classic Princess Ortholite Black Walking Fitness Workout Shoes Women 8.5Balmoral Mens M V B Slipper Boots Olive Green RipTape Fastening (R3A)Saucony Cohesion 10 Running Shoe Women's Size 7 Silver Blue Walking S15343 , Men's Shoes Slippers Slippers men's Consumers First Slippers , Nike Free 5.0 TR Fit 4 Womens Running Shoes 629496 003 Size 6.5 Gray NIBNIKE RIVAL D 9 Chalk Blue White Mid Distance Track Spikes Shoes Womens 6 10 10.5 , Women's Nike Free Run Running Shoes Sz 11Merrell Ladies Encore Suede Slip On 9 Grey (SKU:1VCBAR) - Used , Saucony ISO Series Zealot Blue/Green Running Shoes Women's US 11.5 (P)Nike AF-1 Premium "AF1-82" Old School 2006 Pistachio Basketball Shoe Size 8Mizuno size 8.5M Wave Rider 20 gray pink womens ladies running athletic shoesPropet Life Walker Sneaker - Women's Size 7.5M, WhiteMerrell Vibram Hiking Trail Athletic Sneakers Womens US 7.5 , New Balance Womens - Silver Running Shoes Size 11 (351716)Saucony Womens Kilkenny XC7 Purple/Blue Size 10
"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."