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.American Apparel Lattice Jelly Peep Toe Ballet Flat Sandal Clear Navy Blue 6SAS Softie Tassel & Kiltie LOAFERS Moccasins Womens Size 6 M NAVY Tripad Comfort , PERFECT PRETTY GREEN SHIMMER GOLD SLIP ON WEDGE BODEN SHOES 40/8.5 VERY NICE EUC , Skechers Bobs-Plush Peace & Love Olive Womens Loafers Size 10MEtienne Aigner Women's Carmine Leather Fabric Bit Loafers Shoes Size 9.5 M Black , Axxiom Women’s Cognac Color Faux Leather Clogs Wedges Marnie Size 10M , Tory Burch Chelsea Blue Rhinestone Ballet Flats Size 5 M Casual Career Shoes , Womens BORN Black Leather Upper Mary Jane Buckle Walking Shoes Sz 6.5 M /37 EUARIAT Distressed Brown Clog Shoes Del Mar Horse Bit Sz 6.5Nine West Womens Lightning Leather Pointed Toe Loafers, Natural, Size 10.0 LC1q , p BORN HAND CRAFTED BROWN LEATHER LOAFERS WOMENS 8 MVintage Bamboo National Style Increased within Slipsole Embroidered Shoes Old BeNEW ZARA 2015 BLACK REAL LEATHER OPEN WORK FLATS SNEAKERS SHOES SZ 36EU/3UK/6USKaanas Sahara Mule Sneakers-Women's size 9 BlackLadies' SHOES SHOES TRAINERS CASUAL SHOES TRAINERS SIZE 39Ecco Receptor Black Mary Jane Slip On Driving Shoe Sandals Womens 38/7 7.5Womens Skechers Pink Running shoes size 6Women's Keds Size 7.5 Multi-colored Boat Deck Shoes Canvas SneakersNike Revolution 2 Running Training Gym Shoes Colorful Sz 7.5 38.5 Pretty 554900 , US4-11 Women Flat Glitter Flat Slip On Casual Round Toe Breathable Leisure ShoesNike Women City Loop Shoes Tech Fleece Black White Grey AA1097-001 Size 5 / 6 , NIKE WOMEN'S AIR FORCE 1 HI SE SHOES 12 black grey 860544 002Sperry Size 9 M SEASIDE PERFORATED White Leather Sneakers New Womens ShoesConverse Women's CT All Star Parchment Sneakers 551608C Ivory US 8 RRP $80 BCF72 , Nike 616723 Women's Air Max Thea Premium Low Top Running Shoes Sneakers , Asics Gel Nimbus 17 Women's Yellow / Pink Running Sneakers Shoes Size 10.5Asics T383N Gel Venture 4 Womens Trail Running Shoes Size 8.5 Gray/Pink , ASICS Womens - White Tennis Shoes Size 9 (359550)NWOB Adidas Sneakers Tennis Running Flats Shoes Size 11 11B 11M NEWASICS GEL-Lyte V - Beige - Womens
"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."