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.NATURALIZER SHOES MARY JANE STYLE MAN MADE SIZES -US-6/M EUR-36 CM-23 MINT CONDIDonald J Pliner Sport Womens Shoes Brown Leather Clogs Slides Mules Size 6MWomens Simple Green Toe Navy Hemp Flats 10 M Shoes A061 , BOBS from Skechers Women's Highlights Flexpadrille Wedge Taupe No Box , Womens shoes Montego Bay Club Black with gold Sandal 10 M slip onNEW Zara Black Suede Fringe Studded Flat Loafer Size US 6 / NWOB A32NEW ME TOO GRAY LEATHER FLAT PUMPS SIZE 8.5 M $79Sam Edelman Circus Women's Jadyn Fashion Sneakers Boot Chevron White Black 9.5HELENE ARPELS LOAFERS FLAT SHOES SZ 8.5 AA ( NARROW ) PURPLE LEATHER ITALY , DANSKO Hilde Women's Size US 9.5 / 10 Mary Janes Silver Gray Loafers �b2 , nEW Fashion Rabbit Fur Lined Leather Embroidery Loafer Slipper Mule Hot , Alegria Ballet Flats 10.5 Petal Leather Black Dazzler Comfort Shoes PET-530NEW! New Balance Women's Trail Running Shoes Grey/Pink #wt410ggp 105N dz , ASICS GEL-EXALT 2 Womens Blue/Pink Athletic Running Training Shoes Size 11 (US)Ryka Dash 3 Athletic Shoes - Women's Size 6.5 M, Navy/Pink , Keds Ked's Metallic Womens Sparkle Sneakers Athletic Shoes SZ US 6 M 6M , Saucony Original Jazz O Running Shoes Womens Size 8.5 M (B) Blue S1044-328 , CONVERSE Black Purple Paisley Two Tongue Shoe Chuck Taylor Sneaker Woman Size 7Sperry Top-Sider Brown Purple Tan Dillon Strap Waterproof Shoe Womens Size 8MPUMA Roma Basic Women's White/Light Grey 35357314 Size 7.5 , Grasshoppers Women's Harbor Wedge Fashion Sneaker - Choose SZ/Color , Adidas PureBoost X TR 2 Women's Running Shoes Sz.10 US Grey NWOBNew Nike Womens Nikelab free Transform 5k Running Shoes 878552-001 sz 7.5WOMEN'S 2006 NIKE BLACK & PINK AIR JORDAN 23 SNEAKER SHOES - SIZE 6.5Dr. Martens Shoreditch Cherry Red Canvas 13524603 Women's Boot- Size 10-M , $160 SUPERGA 2095 TWDW Silver Designer High Top Sneakers Womens 6.5 Mens 5Adidas Aerobounce ST W Stability Chalk Blue Women Running Shoes CG4584 Size US 6 , Nike Dunk High 6.0 Shoes Womens 6.5 Pure Purple/Pro Cyan 342257-541 Streetwear , Skidbuster Womens Slip Resistant Sz 8.5 Slip-On Black Action Shoes S5077W FAST!Converse All Stars White & Gold Polka Dot Sneakers Shoes Mens 9, Womens 11
"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."