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.CLARKS 35225 Wo's 6M Brown Leather Wedge Heel Button Mules Open Heel , Merrell Arabesque Suede Leather Slip-on Trail Walking Shoe Women's Size 9Tamaris white leather black patent captoe oxford shoes sz.6.5 , Crocs Womens Suede Clogs Mules Shoes Black, w9 , Bass terri oxfords silver leather & cream canvas nib ret$130 sz 8.5 & 10 , NWT CROCS CROCBAND II.5 NAVY FUCHSIA PINK CREAM 4 5 6 7 8 9 10 11 CLOGS shoes , Funtasma Flat Ballet Red Glitter Bow Accent STAR-16G/R , **Bare Traps Kiah Metallic Slip On Shoes, Women's Size 10M, Pewter , � Teva Performance Ballet Flats size 8 M Breathable Fabric Black Leather Accent , Earth Shore Black Womens Shoes Casual Sandals Sandals Flat With Box Size 7 , Klogs Bambi Women's Display Model Shoes Black Wigwam 6.5 M , Abound Women's Gray Wool Kiley Quilt Loafer Size 7.5MVince Camuto Womens bayana Leather Low Top Slip On Fashion, Black, Size 10.0 pnX , Women's Reebok SMOOTHFIT BLACK Training Workout Shoes Sneaker US9.5 UK7 EUR40.5 , SAUCONY Women’s SHADOW GENESIS Running Blue & White Sneakers US7 UK5 EUR38 , City Shoes Valent Strut28 Womens Black Gold Synthetic TrainersWomen's Bee Embroidery Slippers Slides Mules Shoes Leather Loafers New , Women Platform Wedge High Heel Fashion Leather Sneaker Ankle Boots Shoes zhou8mens LEATHER shoe SANDALS HUARACHE huarache SLIDE ONS *ALL SIZES* , Columbia Athletic Men's Shoes US Size 10.5 Navy and Gray Has Flaws , Everlast Womens Size 7.5 Shoes Maggie 79973 Gray Sport , WMNS NIKE AIR MAX THEA BLACK-WHITE <599409 017> US SIZESWomen's women's columbia shoes size 7 To Rank First Among Similar Products Athletic ShoesNIKE Womens Benassi Jdi 343881-107 WHITE Womens Size 10 , Ecco Women's Biom Fjuel Athletic Shoes Coral Blush Size /US 10-10.5M , Brooks Womens Adrenaline Gts 18 Navy/Teal/Mint Running Shoes Size 6.5 (29395)Womens Merrell Moab Ventilator Taupe J86612 Trail/Hiking Shoes! Size 9.5 $120.00New Womens Size 6.5 NIKE Hyperdiamond 684696-010 Baseball Softball Cleat BlackVasque Gore-Tex -Women's-Mantra 2.0 GTX Hiker - Canteen/Orange Peel -7071 SZ 10 , Keds Women's Anchor Sneaker - Choose SZ/Color
"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."