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.Propet Women's W3205 "Cafe Walker" Brown Leather Mary Jane Walking Shoe 8.5 MWomens Size 8.5 b.o.c Born Concept Brown Leather Loafers/ClogsCLARK'S Oxblood Burgundy Upper Leather Crocodile Pull On Loafers Women's Size 105th AVE WOMENS MINT GREEN SUEDE WEDGE HEEL BALLET FLATS SIZE 7.5/38 MBorn Concept BOC Leather Clogs Black 8$79 JESSICA SIMPSON NALAN PENNY OSCAR BALLET FLATS US 7.5MSchool Issue Primary T-Strap Flat Women's, Black, Size 7.5Clarks Loafers Brown Leather 10 M Croc Pattern Strap Buckle Flats Women Shoes , Klogs Sandy Womens Clogs Shoes Display Model Leather Black Smooth 9 WWork Wonders Dansko Camellia Shoe - Women's Size 10.5, Blue PlaidMatt Bernson Women's Mercer d'Orsay Flats Black / Gold Size 8.5 M US - MSRP $219 , Steve Madden New Slick Black Womens Shoes Size 7.5 M Fashion Sneakers MSRP $79 , Wanted Giselle Memory Foam Dressy Ballet Flats Choose Sz/ColorSperry Top-Sider Women's 7 Seas Mesh 3-Eye Boat Sneakers Berry Pink , Kazakh Men House Indoor Slippers Home Warm felt Shoes Sandals Soft Anti-SlipOld Navy Women Classic Grey Heather Wool Blend Fashion Sneaker Walking Shoe Sz 9Women's Animal Print Sneakers Size 9.5 , Sperry Bahama Fish Circle Canvas Boat Shoe CoralSkechers Womens - White Walking Shoes Size 10 (354242)NIKE Shox WOMENS RUNNING Sneakers SIZE 6 Black And Purple 417103-026 , adidas Liquid Ride - Black - WomensSaucony Womens Excursion TR Running Trail Shoes Sneakers Sz 8 G696Women's LPB Nadia Compense Taupe High Quality FlatsWomen's Urban Outfitters Kitty Canvas Shoes New Varieties Are Introduced One After Another FlatsWomen New Balance Everyday Running Shoe W775LG3 Thunder/Black/Alpha Pink NewBOBS from Skechers Women's Squad-Star Chase SneakerNEW K-SWISS WOMENS COURT PRO II T CMF SNEAKERVANS Authentic (Studded Stars) Red/Blue Patriotic America WOMEN'S 7.5Adidas Women’s Mana Bounce Running Course Athletic Shoes Size US 7.5 B54157 #BRC , NEW BALANCE 577 Shoes Athletic Walking Control Womens Sz 7 wide WW577VW ,
"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."