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.Talbots Moccasins Tassel Flux Fur Lining Red Suede Loafer Slippers Women's Sz 6MBlue Suede Moccasin Casual Shoe, Suede Leather /Sherpa, Womens US 9Christian Siriano Women's Pointy Toe Slip on Flats Shoes Black Gray 9 Wide NewMerrell Womens Black Oil Rubbed Leather Mules Size 7 M , Fashion Women Loafers Round Toe Slip On Shoes Lolita Sweet Flats Walk sizeOLLIO WOMEN'S SHOES FAUX SUEDE BLACK COMFORT BALLET FLAT - SIZE 9 - EUC , Crocs Women’s Walu Black Shimmer Leather Loafer - Sizes 6/7/8 NWOB 202303-060Aerosoles Women's Smart Move Flat, Blue Nubuck, 9.5 M USJ.Crew Slingback Ballet Flats in Black $145 41861 Size 7 Made In ItalyWomen's MERRELL Zoe Sojourn Mary Jane Elastic Straps Vegan Nylon j93840 Grey , Lucky Brand Esmie mary jane womens flats shoes size 6 brown metallic GREATWomen's EASTLAND Gia NATURAL LeatherNew Women's Skechers 34269 Bobs World Sparlerz Flats - Silver Size 7 (L8)LADIES REFLEX WHITE SLIP ON TRAINERS WITH TOGGLE & STUD DETAIL F7054 , Nike Lunar Glide 4 Running Shoes Yellow Synthetic Women8.5Medium (B, M) , Reebok Women's Athletic Sneaker Black/Purple Size 7 Used!!! , Womens Slip On Leather Shoes Sneakers Canvas Loafers Casual Alphabet PlatformBettye by Bettye Muller Black fringe moccasin 8.5M boho chic comfy! , Volley International Womens Casual Sneakers Green Blue size 5,6,7,8,9Sanuk Bianca TX - Grey - Womens , Women's Asics Gel-Challenger Sz 6.5 Sneakers Shoe White Green Athletic Tennis M5Womens Addidas Volleyball Court Shoes Size 9 Black About Red. Clean. , Merrell Reflex II GTK Classic Gore-Tek Hiking Trail Shoes Women's Size 7.5 USUnder Armour Women's City Hopper Jogger - Choose SZ/ColorNike Wmns Classic Cortez Epic Red Blue Women Casual Classic Shoes 807241-641 , Skechers Sport Womens Gratis-In Motion Fashion Sneaker- Pick SZ/Color. , adidas Originals ZX Flux Women’s Running Shoes White Mint Size 8.5 *NEW , CONVERSE CHUCK TAYLOR ALL STAR Low Top Sneakers Womens 7.5 White Canvas ShoesNine West Womens Shireene Textured Slip On Low Top Sneakers Shoes BHFO 5754Straw Hat Panama Size S-M 54-57 Straw Hat Summer hat Leisure hat unisex
"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."