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.Poetic License Desert Star Zebra Print Pony Leather Mary Jane Ballet Shoes Flats , LADIES FLAT ELASTICATED CANVAS SLIP ON CASUAL SUMMER PUMPS/ SHOES F8781Ariat SHOES WOMENS SIZE 8 1/2 B STYLE: 20853 , NATURALIZERS Pre Owned Loafers Womens Shoes Size 6.5M Brown Buy It NowAdrienne Vittadini Kris Women's Ballet Ballerina Peep Toe Flats Shoes Orange 7 MBASIC NEWALK BY BIRKENSTOCK BLACK LEATHER MULES US W 8.5-9 GUCEasy Spirit Say 7W Women's Slip On Leather Shoes Jl 061417B , Womens Sperry Off White w/Blue Stripe Down Back Canvas Sneakers Size 75M (X162) , SKECHERS WOMEN'S SZ 10 BIKERS ASPIRE LEATHER MESH MARY JANES WHITE B25 , Women's Fashion Breathable Wedge High Heel Sneakers Summer Sports Shoes Chic A81Keen Women's Malibu 7.5 Red Mary Jane Dual Buckle Strap Hiking ShoesWomens Under Armour Micro 4D Foam Running Training shoes size 8.5 US Yellow , Skechers Women's Ez Flex 3.0 - Swift Motion Slip-On Shoe , Sketcher Memory Foam Walking shoes 9.5 W New Without Box. , PUMA Womens Suede Classic Wns Fashion Sneaker- Select SZ/Color. , Woman pink and white converse with dark blue pipingNEW Ecco Receptor RXP 1060 Women's Size US 9 Running Trail Shoes , New Balance Womens CW620 Capsule Core Classic Running Shoe- Pick SZ/Color.Nike AJ1 Lover XX SZ 8 Off White AJ1 AO1523-100 NO BOX TOP , Womens Nike In Season TR Memory Foam Size 5 (865595 004) No Box , PUMA Women's Suede Core Platform - Choose SZ/ColorBZ851 SERGIO TACCHINI shoes pink textile women sneakersConverse Women's Chuck Taylor All Star Ox White Silver White , Womens adidas Climachill Rocket Running Shoes Size: 7 Women Color Blue , New Balance Women's W490CG4 Fitness Shoes Gray 4.5 B US NEW , Skechers Onix The Painter Sneakers Black/Mint Paint Splatter Shoes Sz 7 , K-Swiss Womens Modern High Top Fashion Sneaker Beaujolais Plum White Size 11 , Skechers Women's GOwalk Slip-on Sneakers Purple 8Skechers Performance on-the-go Black/Grey, Size 9New Womens Nike Air Elite Closer 4 Basketball Shoes Sneakers Womens Sz 12
"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."