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.NEW Womens S.O. CABANA CREAM Espadeille Flats Loafer Dress Shoe SZ 5� Liz & Co Liz Claiborne Tassel Loafers size 10 M Low Heel Black Leather; Nice! , Natural Soul Women's Black Leather Zip Loafer Shoes Size US 8.5Womens Munro American 8.5 N Bronze Leather and Man Made Slipper LoaferWomens Sperry Top Sider Angelfish Boat Shoes Size US 10 M Purple White PlaidWomen's Vintage SIze 7.5 Cole Haan Metallic Gold Woven Flats Made In ItalyDansko Ann Pewter 6702-970297MEPHISTO Women's Air Relax MOBILS Black Leather Shoes Size US 6 , SAS Women's 9M 'Traveler' Brown Leather Tripad Comfort Oxford Shoe , Acorn Men's Moc Tex/Polar - Black Berber - L , FashionMen Women Canvas Flat Slip On Casual Shoes Sneaker DIY Hand Painted Shoes , ASH A.S.H. KARMA LEATHER BLACK SHOES SNEAKERS LOAFERS SZ 40 / 10 M CROCO EMBOSS , EXCELLENT CONDITION Caslon "Paula" Blue Suede Slipon Loafer (W95713) - 7B , CLARKS Womens Kinzie Leather Closed Toe Loafers, Pewter Leather, Size 11.0 Jmgg , Hush Puppies Classic Walker Women's Fashion Sneakers White/Cream Size 10M NIB , Women's VANS WINSTON Cream+Pink Athletic Fashion Skate Sneakers/Shoes NEWChic Women's Fashion Sneakes Platform Slip On Round Toe Wedge Heel Casual ShoesASICS GEL TITANIUM WOMEN'S ATHLETIC RUNNING SHOES SIZE 9.5 Green GRAY T3B6QCall It Spring Lovaudien Flat Fasion Sneakers, Red, 7 US / 37.5 EUNew Balance 1645 Rock & Tone Shoes WW1645TP Taupe Gray Shoe Womens Size 7.5 B , Women's Gray Saucony Dasis 2 Shoes Size 7 , NEW SKECHERS WOMENS RELAXED FIT BIKERS LAYERED SNEAKERFuntasma Women's Gogo 300UV Neon Orange Stretch PatentNIKE FREE 5.0 TR FIT 5 PRT SZ: WMNS 5 (704695 405) RETAIL: $110.00New Balance Womens Size 7 WX811SS Shoes 811 new sneakersadidas Originals AC7163 : Women's Superstar Fashion Sneakers White/NavyNIKE WOMEN'S AF1 FLYKNIT LOW SHOES SIZE 7 college navy 820256 401Skechers Cali Women's Flex Appeal 2.0-Deja Vu Sport Sandal , Salomon Womens XA Pro 3D CS Green Athletic Hiking Mountain Running Shoes 9.5 , NEW RYKA Women’s Water Resistant Suede Zip Front Sport Walking Shoes SZ 10W ,
"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."