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.Rockport Pink Croc Snakeskin Leather Comfort Ballet Flats Size 5MCLARKS Women's 7.5 Medium Cordovan Brown Leather Slip On Low Heel Slides Clogs , Clarks Bendables Sz 8M Black Patent Croc Print Wedge Loafer Slip On Shoes (A11)Athena Alexander Taffy Scalloped Ballet Flats, Gold Snake, 10 USSperry Red Mesh Boat Shoe Loafer Top Sider Size 8 , MERRELL PLAZA BANDEAU WOMENS 8 TAN TAUPE SUEDE MARY JANE DRIVING SLIP ON LOAFERS , Rockport Adiprene Womens Size 9 W Red/Black Bow Flat Ballet Pump Shoes EUC , DANSKO Fran Women Mary Jane Stitched CLOGS Green Suede Casual Shoe sz 36/5.5-6US , Vera Wang Lavender Label Gold Metallic Leather Peep Toe Ballet Flats Size 8.5 , Merrell 1 Encore & 1 Topo Moc Pro White size 8.5 M Nursing / Work Shoes ClogsLadies Ralph Lauren Solid Black Leather Shoes Size 8M , NEW Cole Haan 2 Zerogrand Stitchlite Ballet Flat WOMENS 9 B Black Knit $130. , A2 by Aerosoles Trend Book Women's Slip-On Flat Shoes, Size 6.5 M - Grey, BlackAriat Yuma Size 7.5 B Boat Deck Shoes Brown Peach Womens Leather 10012908 Flats , Rocket Dog Women's General Cadet Pu Fashion Sneaker, White, 8 M US , Reebok Womens Hexaffect Sport CloudGrey/CrispBlue/White Running Shoes Size 8 , New Balance Barringer 890 rev lite Running Shoes Ladies Size 6.5 Bright NeonReebok Status Classic Leather LTHR Hijacked Heritage Gold Women's Size 6.5Brand New Nike Dunk Low Women's Athletic Fashion Sneakers [317813 161] , Vans Women SK8-Hi Slim Cutout - Mesh white black VN04KZISZNike WMNS Roshe One Hyperfuse BR women lifestyle sneakers rosherun NEW blue , Charolais Cattle Cow Christmas Running Shoes For Women- Free Shipping , ASICS Womens - Gray Running Shoes Size 9 (352068)Asics Gel-Excite 3 Womens Running Shoe SKU T5B9N.9836 Size 7 , NEW NIKE BLAZER MID SUEDE SHOES Womens Sizes Sport Fuchsia/Sail 518171 614 $100.Women's Adidas Advantage Adapt - Black - Width: med - Fashion Sneakers , Keen Elsa Sneaker - Women's Size 9, White , 8.5 M EASY SPIRIT QUIRKY BLACK FABRIC SHOE E360 LINE , Skechers Sport 22532 Womens Breathe Easy Jackpot Fashion Sneaker, Black, 7 M US , Gola Women's Shoes Quota Acid Pink Fashion Sneaker(runs small size up Please
"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."