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.Free People Womens Last Dance Flats Shoes Metallic Rose Gold Size 37 NewNIB Enzo Angiolini Women's Eatilah Black 2 Leather Flat Sandals 7.5M MSRP $89.00 , Dansko Madigan Womens Moc Toe Mule Clog Shoes Brown 8.5 39 Nursing Comfort S57 , Romika Brown Leather Loafers Slip On Shoes Size 37 , Franco Sarto Women's Shimmy Black Ballet Flat Size 7.5 , RRP$180 ESDRA Black w/ gold leather flat shoes -EU37/US 7/AU 6/ , Klogs Reese Women's Slip On Leather Shoes Display Model Black/Lunar 8 MTod's Women's 35 Sz 5 Brown Pebbled Leather Driving Penny Loafers Italy $42514th & Union Womens Black Leather Flats 7 MBernie Mev 37 US 6-6.5 Black Abigail Reef Sling Back SandalsWomen Floral Hidden Wedge Canvas Sneakers Casual Sports Folk Ethnic Travel Shoes , Dansko tan SAVANA mary jane shoes size 40 (dansko100) , Naturalizer Women's Black Leather Lecture Slip-on Oxford Size 7.5WMix No 6 Womens Sarlinas Almond Toe Loafers Black Size 7.0 9SHD , ASICS GEL EQUATION 6 RUNNING SHOES WOMENS SZ 9 BLACK PINK WALKING ATHLETIC EUC , KangaROOS Ladies Retro Pocketpass Sneakers Shoes Size 7.5 in Black , Korea Kakao Friends Brand Men Summer Rubber Sandals Three Striped Slippers , Womens size 6.5 Nike Air Relentless 3 Athletic shoes Gray with teal and greenConverse Chuck Taylor All Star Ox Silver Glitter 135851C Women's 13 Men Size 11Skechers Women's Relaxed Fit Air Cooled Memory Foam Shoes Beige White Sz 7.5 , Cloudtech women's Running Sneakers Beige/Orange Size 9.5 MWomens Sperry Top Sider Gray Mesh Sneakers Size 8M (V950) , Adidas 24 7 women's sneakers size 8.5 brand new with tags , Women's No Name Jungle Bandana Blanc Queensland Athletic Shoes , PUMA Womens Fierce Knit Cross-Trainer Shoe- Select SZ/Color.Skechers 22771 Womens Gratis Light Heart Black Size 8 US #BR9Adidas Stella McCartney Boost ll Womens Running Trainers Shoes Fitness F32466 D1MBT Sand Rocker Toning Walking Beige Leather sz.8.5 Oxfords Wedge/platformTeva Womens DE LA Vina Leather Waterproof High Casual Boots Size 7.5 , New Balance Vazee Prism V2 Running Shoes-Women's size 9D Black
"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."