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.AGATHA-01 New Nubuck Fashion Slip On Casual Women Flats Office Shoes Fuchsia*7.5Brand New Pewter Loafer Metallic Slip On Silver Sandals Loafer Flat Shoe , Renzo Fontanelli Womens Shoes Sz 7 AAAA Elena Slipons Dress Casual Flats Italy , Womens Kensie "LADDONNA" canvas espadrilles cap toe sz. 7.5 NEW!Keen 8.5 Sienna Flats Comfort Canvas Mary Jane shoes Slip On Casual , Puma 9.5 Ballet Flats Shoes Comfort Blue Stripe Bow Slip OnNEW NWT CROCS CROCBAND AIRY FLATS shoes 6 7 8 9 10 ESPRESSO BLACK CANDY PINKCole Haan Womens Campus Pinch Calf Hair Closed Toe Loafers, Dark Teal, Size 6.0Charles by Charles David Danni Ballet Flats, Slate , NICE Women's SAS Tri-Pad Comfort Low Wedge Shoes Slip-on Loafers Black-USA-8.5 S , Foot Prints By Birkenstock Womens Size Euro 36 Shoe Black Leather Loafer ComfortBORN Pewter Blue Laser Cut Leather Bow Toe Ballet Flats - 7.52017 Stylish Womens Mesh Breathable Loafers Slip On Leisure Flower Walking Shoes , New Sam Edelman Black Genuine Leather Slip-on Buckle Block Heel Shoes Sz 7 1/2M , Kenneth Cole Reaction Pro-Time Flats - Women's Size 8M - BlackKlogs Pompei Womens Clog Shoes Display Model Black 8 M , NEW BALANCE 1540 ENCAP WOMEN'S COMFORT WALKING SHOES SZ 7.5 2E VERY GOOD COND.01-13 Skechers 12404 GYMT Women's EMPIRE HEART TO HEART Walking SZ 9.5 , JUICY COUTURE RAYNA Flat Ballet shoes Sz 6 1/2 Blue Beige Silver Twill J170222Chic Women's Flats Slip on Rivet Shallow Mouth Fashion Square Toe Metallic ShoesCole Haan Womens Waterproof Mule Shoes Sz 8.5B Black Suede Slip On Zip Up Euc , Ladies Leather Slippers Brown Shoes suede slip 7 8 9 10 11 12 13 Flip-Flop muleNew Balance WT910GX2 Women's Size 9 Grey/Teal/Pink Athletics Sneakers ZU-1408Asics Women's Gel Zaraca 4 Running Shoes- Mosaic Blue/Pink Glow/Onyx SIZE 8Womens Gola Harrier Low Top Suede Running White Striped Sneakers US Sizes 5-10New Altra Womens Torin 2.0 ParrotBlue Running Shoes Size 5.5New Women's Nike Free Run+2 Running Shoes Electric Green 443816 336 , New Balance Womens Series 600 Running Shoes Size 10 Black White Pink ColorwayASICS FuzeX Rush Running Shoes - Women's Size 12 - Pink , Women's New Balance Ultra Soft Metallic Silver and Pink Size 9
"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."