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.Chinese Embroide Shoes Chinese style embroidered Canvas Shoes4CLARKS Women's Size 7.5 Dark Brown Leather Loafer Dress Shoes Slip OnGrendha Beaded Exotic Sandal **NEW W TAGS $39.95** Sz 9-10 Novo Shoes Brazilian , Fergalicious Womens Shoes Sz 7 Gray "Alana" Ballet Flats Ruffle Bow YMunro Nude Brown Nylon Fabric Bow Flats Size 7.5 Extra WideBORN Brown Soft Pebbled Leather Mules Clogs Shoes Womens Size 8/39 , Cole Haan Country Loafers Women's Size 6BButterflyTwists Black Ballerina Shoes Size 6 US , Nice Blue Leather ARIAT Tassel Slide Wedges US 9B M , SANUK WOMENS PINK KATALINA SIDEWALK SURFERAlegria Leather Mary Janes - Flair Black med 9.5 , Skechers Womens Bobs B-Loved Round Toe Loafers, Black, Size 7.5 bN02Brooks Women's Glycerin 15 Running Shoes Size 9 W Wide Width , Madewell Keaton Oxfords In Pecan Women's US Size 8.5 Brown Leather Dress Shoe , NEW Clarks Ruched Leather Slip-ons Adjustable Strap EVERLAY CODA NAVY 9.5 , Women Light Non Slip Running Shoes Breathable Comfortable Outdoor Casual Walking , Sperry Top Sider Womens Blue Comfort Athletic Shoes Size 8 (250392)women Asics GT 2160 Athletic Walking running Shoes Size 7 T154N , Prince Arch Bridge Tennis Court Shoes Size 7.5 Pink & WhiteNike Vapor Court 631713-100 Women’s Running Shoes US Size 9 Used good conditionWomen's Nike Flyknit Lunar 2 Running Shoes 620658-010 Sz 6 USWomen's Womens~Suede Leather~Driving Shoes~Lands End~6 B~Moccasins~Loafers Bargain Price FlatsK-Swiss Classic SL P-W Womens P Sneaker- Choose SZ/Color. , Puma Women's Fierce Bright Mesh Ankle-High Training Shoes Size 7 Elfin YellowVans Men's/ Women's Authentic Canvas Fashion Sneaker Dress Blue/ Nautical BlueNew Balance W3090OY1 3090 Minimus Barefoot Pink Running Sneakers Women's US 7BDC Womens Trase SE Skateboarding Shoe- Pick SZ/Color. , Propet Women's Washable Walker Walking Shoe, SR Indigo, 7 S US , NIKE Air Womens Sneaker Shoes Sz 10 / 42 ACG Brown Pink Leather & Canvas OxfordSHINY GOLD..PLATFORM..SNEAKERS..w STUDS, SPIKES..STEVE MADDEN..Sz 9 ,
"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."