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.NATURALIZER N5 Comfort Slip On Wedge Loafers Black LEATHER Uppers Women's 6 MNIB NINE WEST LADIES SIZE 61/2 M PANDEY SLIP ON SNEAKER WHITE & STRIPE , AR35 Ellie Casual Round Toe Ballet Flats 684, Cognac, 7 US , Born Women's Brown Leather Wedge Slip On Mules w/Buckle Size 6 U.S. / Euro 36.5 , Steve Madden Womens Size US 7.5 Flats Silver Snakeskin 'Kobraa' Shoes A6Kelly & Katie Womens lovelian Closed Toe Loafers Navy Size 7.5 QPz4 , Josef Seibel Womens Black Patent Leather Comfort Shoe Single Strap Size 41 , Born Mary Janes Loafer Slip On Brown Leather Strap Womens Shoes Size US 8MFERGALICIOUS by FERGIE Womens WISTERIA Taupe Ballet Flats 6M (D2108F1900)LADIES SHOES/FOOTWEAR - cabello boot 5626ss black size 39/8 , $120 FitFlop Womens Superskate Slip On Loafer Shoes, Silver, US 7.5KEDS WOMEN'S SHOES GLIMMER NAUTICAL NAVY WF57107 ORTHOLITE FOAM TECHNOLOGIES , US INDIAN WOMEN SHOES SLIPPER HANDMADE FLIPFLOPS TRADITIONAL LEATHER JUTI DD1000 , Merrell Continuum Women's Blue Water Shoes - US 7 ()Girls Ladies Athletic Running sport walking Breathable Sneaker Casual shoes JY61 , NICE SKECHERS SHAPE UPS WOMENS 11809 BKW STRENGTH BLACK WHITE Size US 10 M , Mizuno Wave Hakate Women's Multi Color Running Shoes - US 8 () , Women's SKECHERS RELAXED FIT BREATHE EASY ALLURE 22535 Blue Slip On Shoes NEWWomen's Asics Gel-Contend 3 Shoes Sneakers Size 8D Running White Gray Mint W1 , New! Womens Skechers 12492 Empire Big Winner Slip-On - Gray O46 , Nike Air Max Thea LOTC QS Black/Black-White 847072-001 sz 8.5 New York City NYC , Reebok Classic Freestyle Hi Gable Gray Sz 7.5 New In Box! Originally $85 , Women's Womens Keds Size 7 Beautiful Athletic Shoes , Women's LADIES' TENNIS SHOES Excellent Craftsmanship Athletic ShoesNEW SKECHERS WOMENS GOWALK LITE BREAKOUT SLIP-ON SNEAKER , Skechers Simply Sweet Running Women's Shoes Size 5.5Asics GT-2000 Pink/Orange Women's US Size 9 (B4,20) , Lifestride Lime Green Leather Flower Maxine Sandals Square Heel New in Box Sz. 8 , Tennis Women Shoes Hot Sale All-match Women Shoes Lacing Low FlatNEW Under Armour Womens Glyde TPU CC SOFTBALL CLEATS Blk/Wht/Slvr 9.5 FREE SHIP!
"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."