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.Easy Anti-Gravity "Treasure" women white leather upper loafer shoes size 8B , New women's shoes ballet flat ballerina synthetic casual fluorescent orangeSAS Womens TriPad Comfort Black Leather Slip-On Penny Loafer Shoes Size 71/2 n , SAS Womens Tennis Shoes Walkers 9.5 S , Born Concepts Brown Suede Stretch Mary Jane Flats Womens Size 7.5 M*SPERRY Womens 9 M Zuma Fashion Sneaker Charcoal Gray Canvas Slip On Shoes , Easy Spirit Addisat Clog Mules Tan Suede Size 8.5 Wide , baretraps Womens Olivia Dress Penny Loafers Slip On 6.5 NEW$325 attilio giusti leombruni/agl gray suede rhinestone toe flats 40 10 9.5 , Vince Berlin Blackberry Calf Hair Slip-On Sneaker, size 8.5 retail $295 , New Anthropologie Rani Leather Ballet Flats Jasper & Jeera Gold Silver Sz 7.5 , BX746 J. K. ACID shoes bronze black paillettes women slip onWomen Flat Summer Loafer Slip On Moccasins Beach Traveling Pregnant Woman Shoes , Bruno Magli Womens Mules black Leather Slingback block Heel Shoes Size 6.5Cole Haan Womens Loafers Shoes Leather Size 8 AA Style D15762Tahari Women's TA-Estyn Ballet Flat, Black, 7.5 Medium US , RIEKER Antistress Mary Jane Women's Size 8 US | 39 EU | 6 UK RED Leather StrapsBCBG Max Azria Moneli Army Green Ballet Flats Size 7 M , Mens Slipper Snoozies Mules Christmas Gift Stocking Filler , Nike Womens Air Impel sneakers 37707-041 size 10Reef Women's Rover Low TX Fashion Sneaker, Black Camo, Size 6.5Womens Ladies Mid Top Sneakers Athletic Casual Shoes Black Boots US_7 8 9 10 11 , NEW BALANCE WL574ESV Womens Sz 8.5 Lilac Suede Classic Casual ShoesRocket Dog MADOXOC Womens Madox Orchard Canvas Cotton Fashion Sneaker , Steve Madden Women's Glamour Fashion SneakerNIB WOMENS PUMA SKY II 2 HI EXPLOSIVE BLACK PATENT RIHANNA FASHION BOOTS SNEAKER , Dr Martens Made in England Women's Size US 9 Shoes Leather Oxford AW004 , Skechers Shape Ups 12320 Womens Size 8.5 Black Blue Toning Walking Shoes , NEW Nike Court Borough Mid Black White 9 , ASICS Gel Nimbus 18 Pink Running Sneakers Womens Size 11 Very Clean ,
"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."