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.Lucky Brand Leather Open Toe Back Strap Buckle Slip on Flats Womens Sz. 8.5 M , 1 LEFT SHOE NWB KAREN SCOTT OLLIE TAUPE MANMADE FLAT SIZE 7.5M , New Womens LifeStride "Invest Too" Slip-On Flat Shoes Size 7 M Black Soft System , Rieker Antistress Perforated Cutout Wedge Mary Janes Women's EURO 41 (US 10) , Crocs slip on ballet flats - black size 9 , Giani Bernini Womens jileeseoro Closed Toe Loafers, Gold/oro croc, Size 9.5 , Women's Life Stride Leather Brown Women's Loafers Size US 7.5 M , LifeStride Tada Slip-On Loafer - Women's Size 7W - Gray (NEW!) , NYLA Women’s Sz 8 Black Shoes Loafers Vegan Leather Jazz Loaf New NIB USA , **Cliffs Shea Flats Women's Size 11m BlackVince Bray Loafers Hydrangea Blush Pink Velvet Size 9.5Naturalizer Becca Flats - Women's Size 7.5 W, BeigeNurse Mates Harmony Black Loafer Womens Size 8.5 W , Terralam Australia Mid Casual Shoes, Brown Distressed, Sheeskin/Lea, Women's 7.5 , Columbia Women's Drainmaker III, Size 6.5, Quarry-Candy Mint Color, New , Skechers Relaxd Fit Breathe Easy Casual Shoe, Taupe, Womens US Size 6Drew Juniper Mary Jane Mule Womens Shoe Size 7.5 Black Leather Comfort Orthotics , Realtree Ms Cougar Pink Gray Camo Hiking Athletic Shoe Women's Size 11MWomens Saucony Grid Stratos 5 Silver Running Shoes Size 10M (C912)under armour Sneaker Ladies Size 6 1/2 , Nike Free 5.0 Running Shoes Women’s Size 8.5 US Excellent ConditionMerrell "Moab Ventilator" blue and gray hiking shoes. Women's 7.5 (eur 38) , Women's Betsyville Gold flats Outfall Flatsadidas Originals Women's Superstar Tracktop, - Choose SZ/Color , Puma Repli Cat III 303588 White Driving Running Training Sneakers Women's US 11 , Ryka Women's Grafik 2 Cross-Trainer Shoe, Black/Grey/Pink, 8 M US , NEW NIKE DUNK LOW Womens 7 (5.5Y) LTD NIB sb NR , Vans Old Skool Zip Leather Wind Chime Women's 9.5 Skate Shoes NewNew Women's Adidas Pink Black Anja Low Suede Leather Trainers Shoes Sz.5.5 EU.36NWOB Diadora Women's ACTION III Ultramarine Blue Bonnet Athletic Shoes Size 7
"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."