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.02-1352 Nine West Saige Half d'Orsay Flat WOMEN'S SIZE 7.5M , Cole Haan Pinch Maine Classics Womens 6.5 B Brown White Slip On Loafers , DANA BUCHMAN Womens Darcy Red Slip On Flats 1.5" Heel Bow Silver Accents Sz 9 MClarks Cloud Steppers Sillian Glory Womens Comfort Shoes Size 11, Burgundy. , Keds Sport Women Green Suede Slip On Loafer Size 6M Pre Owned , New Womens Casual Walking Lightweight Gym Trainers Slip On Diamante Pumps Shoes , TS35 Zuly Cutout Peep Toe Ballet Flats 023, Black Snake, 8 W US , Ecco Gray Shoes, 8 1/2m, Open toe and closed heel, low wedge, silver tone buckle , Women's Sperry Top-Sider Boat Shoes Sneakers Size 8.5M White Sequin Casual O14Steve Madden Women’s Size 7.5 STUDLYY Flats Loafers Black Silver Spiked StuddedDIMMI, ZEN FASHION SNEAKER, WOMENS, GREY, LEATHER/ FABRIC, NEW WITH BOX , Sbicca Womens Rafa Tan Flats Fashion Loafers Shoes 7.5 Medium (B,M) BHFO 3726Blue by Betsey Johnson Women's SB Joy Ballet Flat, US Size 5 MEcco Kelly Ballet Flat Black Oiled Leather / Size 37 /US 7 , MARC BY MARC JACOBS Silver cat flat sling back women size 37/7 EUC , Ecco Womens Ballet Flat /7-- Pick SZ/Color.Vince Camuto VC-KANTA Womens Kanta Loafer Flat- Choose SZ/Color.NIB CREAN LINEN LUCKY BRAND LK-AISAH WOMEN'S SANDALS SHOES SIZE 6.5MWomens Nike Hyperdunk 2016 TB Basketball Shoes 9.5/41 White Black 844391 110 , Vans womens size 4 low topsWomen's Skechers GoRun 600 Control - Lime Green - Width: med - Cross Training , New Balance 500 Womens 10 M Running Shoes Black Blue WR500BB Sneaker Training , adidas Revenergy Mesh Boost Womens Running Athletic Trainers Sports ShoesJSLIDES Flynn Slip-On Woven Suede Sneaker in Gray Size: 7 , New Balance 1500PB3 Running Shoe - Women's Size 9 D, Wide Neon Pink/Black , New The North Face LiteWave Explore Running Hiking Trail Shoe Boot 6.5 , New PUMA Womens Rbr Rider TotalEclipse-chine Walking Shoes Size 5Adidas Tracerocker Women’s Gray Green Tennis Sport Sneakers US 10.5 M Shoes A984 , Skechers D'Lites Women's Size 9 Black Slip On Clog Tennis ShoesSkechers Women's Galaxies Witty Talk Sport Active Sneakers- Size 7.5 (Gray)
"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."