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.Penny Loves Kenny Women's Aurora Ballet Flat, Pink Pineapple, Size 9.5 , Lands' End Weatherfield Yellow Quilted Hiking Shoes, Womens 7.5B, Worn Once , � Skechers Classic Slip Ons size 8 M Black Glitter Fabric; Wrap Over ToeWhite House Black Market Pointed Ballet Falts Black Leather Womens Size 7.5ECCO Ladies Brown Leather Bicycle Toe Flat Oxfords Size 38 USNew Lucky Brand Cristley2 Womens Size 10M Black Flower Print Leather Flat MulesLadies Clarks Flat Pumps Glove PuppetSesto Meucci metallic silver espadrilles (size 11) , NEW Women Ladies Casual Outdoor Sneakers Fashion Comfortable Shoes White 5603 , PLEASER Womens Sexy Classic Ballet Flat Shoes Bow Accent ANNA-01 Baby Pink , Hi-Tec Women's Haraka Black/Purple Sneaker 7BMERRELL Caper Dark Brown / Lime Comfort Shoes Women's Size 38 / 7.5TRENDSETTER SUE BROWN TEXTILE UPPER NICE WOMENS 8 BOOTS see photos-detailsSalvatore Ferragamo Women's Size 9.5 3 A Brown Leather Dress Shoes BOWSWomen's Vinse Camuto Evy Black Flats Size 7 M NEW , Women's ASICS Gel-Noosa Tri 8 Running Shoes Size 6.5 , Tower 10 Smash Leather Sport Shoes Sneakers Size 9.5 NEW Brown , FOOTJOY LoPro Women Golf Shoes Soft Spikes Size 9.5M Black/White Leather , Nike Tennis Shoes Flex Trainer Athletic Running Sneakers Sz 8 women free shipMizuno Wave Rider 19 Running Shoes, Slvr/Ppl/Grey, Women's US 9Keds Womens US Double Decker Perf Jute Sneakers Size 9 NWOBMerrell Women's Barefoot Contour Glove Multisport Running Shoes Black Size 7 M , New!!! Women's Skechers Wide Width (style WH) Black Slip On Shoes 3Y , Womens New Balance WX711OG2 Cross Training Shoes NIB , Asics Gel Flashpoint Women’s Pink Blue Yellow Tennis Shoes 11 EucAdidas Tubular Shadow Women's Shoes Core Black/Core Black/Cloud White ac8028Skechers Women's Breathe-Easy Charmful Fashion Sneaker , Nike haurache run size 8.5 ladies blacked out stealth joggingSalomon Women's Sonic Pro Running Shoes 379173 Purple/Green, Pre-OwnedKONHILL Women's Lightweight Casual Walking Athletic Shoes Breathable Mesh Pink, ,
"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."