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.MERRELL VENTED LEATHER SLIP ON WOMENS SHOES SIZE 9.5Ellen Tracy Flats Ballet Gold Color And Beads Flowers women shoes Size 8 , Cute ladies SIZE 7.5 BLACK LEATHER slip on loafer HUSHPUPPY Gently WornSize 11. Berries By Aetrex Brand New In Box. Cocoberry Slip OnNew Orthofeet Women Wichita Tan Washable Shoes Sz 6.5 4E XXW NO INSOLES , Clarks Womens Skip On Clogs Brown Shoes 9MNEW Naturalizer Natural Soul Fanna Loafers Black Patent Croc 7MAnne Klein AK Sport Yolanna Women's Metallic Taupe Sneaker Mules US 7 M B704Merrell Plaza Strap Olive Green Suede Brown Leather T Strap Shoes Womens Sz 8.5 , Seychelles Campfire Flat - Women's size 7 - Taupe , LADIES SHOES/FOOTWEAR -Cherry Time gunmetal slide , DKNY hypebeast womens shoe sz 6,5 eu 37Wanted Shoes Womens Kristy Closed Toe Ballet Flats, Silver, Size 8.5Ecco Women's Shoes Size 39 Open Toe Ankle Strap WedgeFILA Memory Sprint EVO Athletic Shoes - Women's Size 10 - Multicolor , Brown Suede Brookstone Slide Slippers us XL 11-12 Shearling Lined Worn Once?Brooks Ravenna 5 Athletic Running Sneaker Shoes Women's Size 8.5 , Asics GT 2000 Teal/Pink Running Shoes Women's US Size 6.5 (C2,4)New Balance 501 SL501BPO Womens Shoes Green Size 12 M , Women's Nike Free 5.0 Running Shoes Size 8.5 US , Women's Skechers Womens Ultimatum Training Shoe Big Clearance Sale Athletic ShoesWomen's sperry top sider womens 6.5 Be Novel In Design Flats , Skechers Flex Appeal 2.0 Womens 12756-BKAQ Black Aqua Training Shoes Size 9NIKE Women's Size 8 Roshe Two Flyknit Hi Boots 861708 MSRP $225 Black/White , New! Sperry STAR WARS Cloud Slip On Droids Sneaker C3PO R2D2 Women Size 6 , W Nike Lunarepic Low Flyknit 2NIKE AIR PRESTO CAGE Womens 9 Mens 7 Cloudburst Black Blue *RARE* FREE SHIP , Farylrobin x Free People Womens Vegan Pearson Menswear Sneakers Nude Size 6 New , Women's UNDER ARMOUR ASSERT 6 1266252 White+Gray Athletic Running Shoes NEW , Adidas Shoes Blue White Womens 8.5 Sneakers Running SC8
"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."