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.Sofft Flats Black Leather Shoes Slip On Dress Shoes Flats 10 M LeatherFranco Sarto Women's Brently Black Patent Leather Slip-On Loafer Size 8 M , White Mountain Scotch Moccasin Loafers 059, White, 7.5 USRose Petals by Walking Cradles Women's CasualSlip On, Black - Size 10M , Aerosoles High Bet Flats Bone Nubuck/ 6.5 M New In Box , Drew Black Leather Orthopedic Mary Jane Comfort Women's Walking Shoes US 11 N , Born Brown Womens Leather Slip On Wedge Heel Clog Loafers Shoes 9.5/41 B9119 D1PAUL GREEN ' NICKY' COFFEE SUEDE LOAFER- Size US 6.5/(P36)Beverly Feldman Naked Truth Womens Paisley Brown/Multi Slip On Flats Size 6Gentle Souls Bay Braid Flats Size 7 Pewter MetallicRalph Lauren Brown Suede Buckle Strap D135 Loafer Womens Shoes 9.5B EUC SpainClarks Womens Size 10 Daelyn Monarch Aubergine Purple Suede Shoe Comfort NEWnike air max women size 6.5Vans Attwood RRP NOW .99 TO CLEAR ONLY , Brighton Jerri Loafers Shoes, Black, Size 7.5NKEDS CASUAL ATHLETIC SHOES / MULTI COLOR ( SIZE 6 ) WOMEN’S , Asics Training Shoes Sz 9.5 Speva Dynamic Terrain Cradle Ahar TN288 Grey Womens**Adidas Cloudfoam QT Flex Athletic Shoe - Women's Size 9.5 - GreyFila Womens Vitality V Running Shoe- Pick SZ/Color.Nike Black Women's Shoes Free Run 2018 Running Sneakers Size 9.5 M Lsr26-519 , Womens Breathable Wedge Heel Casual Fashion Slip On Shoes Woven Sports Sneakers , Women's Skechers Sport Women's Breathe-Easy-Sweet-Jam Sneaker Queensland Athletic ShoesNEW SCHOLL ORTHAHEEL X TRAINER WOMENS COMFORTABLE CROSS TRAINER SHOES , NIKE AIR MAX IVO WOMEN`S SHOES TRAINING RUNNING SNEAKERS NEWSkechers Goga Mat Go Step Women’s Gray Velvety Walking Shoes Sz 9.5 /CHARBrooks Ariel Womens Running Linear Platform Shoes Size 7Superga 2750 Waxed Suede Sneaker, Women's Size 8, PinkVasque Women's Talus Trek Low Black Olive/Damson Ultradry Hiking Shoes 8.5M , ASICS Womens Gel Kayano 23 Silver/PinkGlow/ParachutePurple Running Shoes Size 8 , Women's Brooks Gylcerin 14 Shoes Sneakers Size 10B Running Red Pink Gray T4 ,
"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."