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.classique Women's Ballerina shoes patent leather Navy flats, Size 9 WNEW! Merona Tan 'Noele' Pointed-Toe Slip-on Flats NWT FAST SHIP! , 02-2848 Vaneli. Women's Solana Ballerina Flat SIZE 11 M , PawPaw Ballet Flats Size 5/6 M Blue Denim Stars Print Rubber Soles Slip On , Mlia Lady Womens Casual Slip On Loafer Moccasins Flats Driving & Walking Shoe...L.L. Bean Signature Handsewn Brown Penny Loafer 7.5 D RETAIL $139Biviel flat toe leather shoe women size: 39 color: Brownish , NEW Womens STEVE MADDEN Ibiza Coral Synthetic Flats Shoes , KEEN Casual Sneakers, Women's 7, Brown w/Red , ☆SALE☆ ENDING SOON! Lucky Brand Cahill Black Loafers 8.5 Butter SoftEcco Cayla Tie Oxford Women size 39 US 8 8.5**Clarks Danelly Adira Flats, Women's Size 9.5 W, Black , K-Swiss Limited Edition Women White Leather Size 8 US 39.5 EUR Trainers SneakersHarajuku Star Pattern Women Men's Hand-painted Canvas Shoes Boy Girl's Sneaker , Women Platform Wedge High Heel Fashion Leather Sneaker Ankle Boots Shoes 2ColorsMarc Jacobs Womens Red-White-Blue Mercer Skate Sneaker-Sz US 8-Retail $295Logo Lori Goldstein White Crackle Leather Diane Slip on Mule Sneaker 6 SALE , MG35 Brooke Slip on Low Top Sneakers, Sand CanvasWomen Cotton Blend Breathable Fashion Sneakers Platform Wedge Creepers High HeelVANELLI italian Sport AMYNTA Slide Loafer Mules /Slip on US 7 M TAUPE MSRP $135 , Everlast Sport Women's Lauryn Athletic Running Shoes Black Medium WidthWomen's NEW 1789 CALA WOMENS ESPADRILLES Linden, Fashion Athletic Shoes , NEW NIKE SPORTWEAR PRIMO COURT MID MODERN WOMEN SHOES BLACK (861673-002) SZ 9.5Women's Nike Zoom Vomero 11 Running Shoes NEW Grey/Red/White MSRP $140Adidas Gazelle Primeknit W Easy Green BB5210 US Women Sz 6-8 PK Mint White Sale , NEW PUMA WOMENS SKY HI BBALL BASKETBALL CLASSIC HIGH TOP SNEAKER SHOES 10 , VANS Chukka Moc (DX) Suede Black/Blanc White WOMEN'S SIZE 6New Balance Womens W630ra5 Black/AlphaPink/MetallicSilver Running Shoes Size 8Puma x Fenty by Rihanna Bow Sneaker - Purple - Womens , Gotta Flurt Women's Confused Plasma Hi
"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."