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.Karen Scott Hartley Women's Brown Leather Buckle Accent Loafer Slip Ons Sz 6.5M , Sperry Top-Sider Ariela Women Ballet Flats Gray Silver Metallic Woven Sz 6 NEW , 712 NEW Lewit Cara Blush Leather Pointed Toe Slip On Mules Women's Size 37 M , MID WEST Sz 8 YELLOW Clogs Wellies Wellington Rubber Rain Garden Galoshes ShoesCliffs by White Mountain Halfrida Black Ballet Flats Shoes Women's Size 6M , WOMENS 8 B M 86166 LANDS END Jet InkBlack Suede Leather Clogs Shoes Slip On Used , Metallic Patent Loafer Royal Blue Loafer Shoe Flat Pewter Shoe Primark Women , CROCS CARLIE CUT-OUT CLOGS SIZE 9WFranco Sarto Womens faryn Closed Toe Slide Flats, peach le, Size 9.0 0HMCAnne Klein Women's Overthetop Ballet FlatWomen’s 9½M Apartment 9 Mary Jane’s New Dark Brown 1½” Heels Hook & Loop Close , Eastland Carly Slip On Loafer- Size 7Women's Skechers Mules - D'Lites - A NEW LEAF - Navy - New!!Bibi Lou x Free People Womens Madison Platform Wedge Shoes Black Size 38 NewLevis sneakers Size Womens 7.5 , Womens Running Sneakers Casual Athletic Breathable Walk Sports Shoes jufeng , Clarks Wave Walk Loafer Slip-On Women Sz 7.5W Brown Leather Casual Walking (BE2)Nike Jana Star Waffle 6 Spikeless Women's Track Shoe-Style 525157-603, Size 11.5 , Women's Brown Underground Attitude Logger Casual Shoe, Size 8Nike W NK DRY SHORT ATTK TR5New J.CREW Tretorn Tournament Sneakers Seafoam Green Mesh Women's Size 9 , Women's New balance 515 Women 8 ngenious And Practical Athletic Shoes , Nautica LW0021 Womens Lubec Mid Fashion Sneaker- Choose SZ/Color.WMNS Nike Air Max IVO Women's Running Shoes, 580519 416 Size 7.5 NEW , Naturalizer Womens Jetty Fabric Low Top Zipper Fashion taupe leather Size 11.0Mustang horse Print Christmas Running Shoes For Women-Free ShippingBrooks Womens 1202471B057 Silver/Grey/Rose Walking Shoes Size 9 (24769) , Saucony Womens Zealot Iso 2 Running Shoe- Select SZ/Color. , Superga 2750 Suew Pyper Sneaker, Women's SIze 39 (US 8), PinkWomen's YOU by Skechers - YOU - Charcoal - New in Box ,
"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."