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.xsensible Shoes brown leather Oxfords sneakers size 39 or 8.5 WomensGuppy Love by Blowfish size 9 Pink Flats Round Toe Slip on Shoes WomensPakistani Indian Ladies Kolhapuri Leather Handmade Chappal / Sandals , style and co Sparkling Flats 9.5Espadrilles by I.D. Required, BaJa Canvas Women's Sz 10 M New"Lao Beijing" Brand Classic Ladies Canvas Comfortable Flat ShoesADIDAS soft Peach Canvas Flats Slip ON Women's Sneakers Size 9 , US TRADITIONAL HANDMADE JOOTI WOMEN SHOES LEATHER MOJARI FLIP-FLOPS KHUSSA SS53Sam Edelman Cali Espadrille Flats 776, Black, 9.5 US / 39.5 EU , Fashion Shoes women's Yellow Leather Moccasins Shoes sz 39 24.5 US 9 EUCKlogs Isabella Women's Leather Clogs Display Shoes Black Kpr 7 MDansko Women's Green Suede Mary Jane Sandals Size US 9.5-10 / , Born Haddon Women Clogs Sz 7 Gray Metallic Leather Slip On Platform Shoe , Skechers Relaxed Fit Reggae Fest Dory Slip On - Women's Size 9, Navy , Skechers Comfort Air - Just A Lil Knit Navy Womens Sneakers Size 11M , New Women's Skechers Slip On Athletic Casual Shoes 22406EWR Bungee SIZE 7 , Merrell Women's Hiking Shoes Hilltop Ventilator J098328 Size 7.5 Trail Brown Red , New Balance 695 Running Shoes, #KJ695BY, Slv/Pink/Org,Women's US ~7.5 or 6 YouthAdidas Shoes falcon Elite Women’s 9 , Sam Edelman Womens Baylee Soft Silver/Fog Grey Fashion Sneaker Size 8 (29872)adidas Original Gazelle Sz 11.5 US Womens Vapour Pink Sneakers Trainers ShoesMERRELL brown sugar blue heaven Select dry Hiking Boots Women's 7.5 Unifly , Skechers D'lites Womens 8.5 M Mules Slip On Sneakers White Leather Casual ShoesNew Balance W1150GB1 Women's Running Shoes Size 6 MediumVince Blair 5 Slip Ons- Women's sz 7 M Woodsmoke , nike air max 1 ST (GS) trainers 653819 105 sneakers shoes , Reebok Women's RealFlex Run 2.0 EX Shoes NEW AUTHENTIC Pink/Yellow/Gravel V53907Women's Nike Primo Court Mid Suede Fashion Sneaker Shoes-size 8Women's ADIDAS ClimaChill Sonic Bounce Running Training Shoes (S78254) , adidas Women's Hoops 2.0 Mid W Hi-Top Black/White Medium #DB1226 ,
"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."