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.Bare Traps Womens Hastings Fabric Low Top Walking ShoesWomen's Azaleia Mary Jane Slip On Shoes - Navy - Size 7.5Natural Soul By Naturalizer Size 6.5 Mules Brown Suede Leather Slide On ClogsKS35 Jazmin Loafer Flats 933, Black, 8.5 USWomens Reef Slip On Shoes Size 9 Brown Canvassapphire-61 New Slip On Synthetic Casual Women's Ballet Flats Shoes Black , Minnetonka Women's Brown Suede and Fabric Moccasins / Sz 7 MDouble Buckles Women Soft Canvas Embroidered Flat Platforms Denim Cotton Shoes6 Ivory Cream Beaded Flats Handmade Silk Indian Khussa Wedding Bridal ShoesCorso Como Surrey Black Leather Women's Flats Sandals Size 6.5 MPuma Mostro Leather Athletic Shoes Women's Size 38 / 7.5Nike Free 5.0 black and coral sneakers, Sz 7.5 , New Skechers BOBS Womens Luxe Sparkle Dot Slip-On Espadrilles Shoes Size 9 (M)Nike Initiator 394053-481 Blue Womens US Size 8.5 CM 25.5VANS New Camden Stripe Linen Vault Lady's size 7PUNKROSE Pink Lightening Bolt Athletic Gothic Rose Sneakers Women Shoes Size 8 , New Balance Zip 1306 WR1306SP Athletic Running Shoes Women's Size 10 BWomen's Nike Free TR FIT 2 Cross Training/ Running Shoe Sz 6 US , Womens Rhinestones Mesh Hollow Shoes Casyal Muffin Sport Sneakers Trainers White , Ed By Ellen DeGeneres Chapamule Sneaker Women's size 9 M , Nike Roshe One White/White-Black Grey Women's Running Shoes 844994-101English Springer Spaniel Halloween-Running Shoes For Women And Kids-Free ShippinNike Women's Flex Experience RN 5 Running Shoe Size 12 White Wolf GreyNew Sam Edelman Black Leila Beaded Embellished Bird Shoe Sneaker Sz 10 M , New Keds 17ss Triple Decker Mini Daisy Sneakers Women Navy Casual shoes WF56499Preowned Women's Size 8 CONVERSE BRAND PINK One Star Sneakers , Skechers Women's Go Walk Lite-15372 Wide Sneaker-Select SZ/ColorSkechers Women's Active Breathe Easy Lucky Lady Shoes AB4 Chocolate Size 10 , Keen Women's Presidio Hiking Brown Leather Boots Shoes Size 11 , Sam Edelman Women's Levine Sneaker - Choose SZ/Color ,
"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."