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 Everyday Active Air Womens Blue 6 1/2M Pumps 85268 Leather ShoesVintage Cole Haan Loafer Women size 6.5 M Tan Leather , WOMENS Blue Wool CHACO "BAYOU" Slip-On Sport Loafers 40/9 M , AUTHENTIC TODS WOMEN WHITE & BLUE DRIVING SHOES /FLATS SIZE 7.5 MED~ITALY~ , NEW WOMENS LIFE STRIDE DARK BLUE TIPSY MOC SHOES FLATS SIZE 9.5 W , Lucky Brand Emmie Round Toe Ballet Flats 568, Shady Spruce, 8 US / 38 EUReport Women's Baines Ballet Flat, Black, 9 M US , ROMIKA CASSIE 21 BLACK LEATHER SLIP ON WEDGE BALLET FLAT Size 37 , Jon Josef Gentry Jaguar Loafer Animal Print with TasselsRockport Women's Black Leather Shoes 8.5 MKlogs Womens Leather Shoes Napoli Blue Spruce 6.5 MAsics Hyper Rocket Girl Women's Size 6 (Euro 36) Track Spikes GY753 Silver PinkNew Balance M3068GBL D Grey Blue Men Sports Sandal Slides Slippers M3068GBLDWomens danskin now shoes size 6 black white pink , Grasshoppers Avery Athletic Sneakers, Women's Size 7W, Black NEW , DIESEL MOSLETTE COMFORT CASUAL WOMENS SZ 7 TAN & GREEN SUEDE LEATHER SPORT SHOES , Apex Women's Lenex Walker Walking Shoes X821 White Size 4.5MAsics Onitsuka Tiger HN567 Women Athletic Shoes Sneakers Size 7 Orange SampleWomen's Womens Adidas eqt support adv Good Design Athletic Shoes , Pleaser Pink Label Women's Fab 422 Open-Toe Pump Ivory Satin Heels , Skechers Skecher Street Womens Side Bling Fashion Sneaker- Select SZ/Color.NIKE PRESTO FLY RUNNING WOMEN SHOES SIZE 9.5Merrell Avian Light Ventilator Waterproof Bracken Trail Sneaker Women's US 8 , Women's Brooks Vanguard Sneaker royal blue size 6.5 USA 37.5 EURMerrell Barefoot Women Pace Glove Running Athletic Shoes Size 8.5 Black Omni-Fit , New Balance WRT580 Women's Shoes WRT580GF WRT580GM WRT580RH WRT580XB , Vasque Talus Women's Black Olive/Damson Hiking Shoe 8MNew! Women's UA Micro G Assert 6 Black/White/Pink SZ 8 1266252-001 K8 , 02-88 Brooks Glycerin 16 Women's Running Ebony/Green/Black SZ 9.5B , Nike ZOOM STRIKE Womens Black White Grey AJ0188-001 Athletic Training Shoes ,
"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."