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.Nine West Women's Beachinit Metallic Ballet Flat Gold 9M , $80 size 7.5 Anne Klein Daneen Black Leather Loafers Womens Casual Pumps ShoesEtienne Aigner Townsend Black Leather Loafer Shoes Size 9.5M.Women’s Size 9 Soludos Blue White Striped Canvas Loafers Espadrilles FlatsShoes Flats Beverly Hills Polo Club Ballet Gold Shimmer Bling 7 MediumTory Burch Womens 6 Pink Sheepskin Suede Moccasins Loafers Flats Shoes fmn , Clarks Artisan Ballet Flats Black Leather 6 M Loafers Active Air 87360 ShoesWomen's Earth Angelica Flats Loafers Shoes Size 6.5B Black Leather Mary Jane C12 , LADIES SHOES/FOOTWEAR - Devalverde shoe 160 navy , Tods 10.5 Silver Peep Toe Flats Ballet ShoesNew Women's Skechers 34366 Bobs Spotlights Casual Flats Sz 6.5 (L18) , Ladies Cole Haan Black Nubuck Slip-Ons 8 Med *2 TRAIN AUTISM SERVICE DOG 4 SON*Nine West Royalli Womens Ballet Flat- Choose SZ/Color.Women's Silver Leather Chuck Taylor Hightops, Size 6Purple Sneakers sz.11M Sonoma Sport Tennis Shoes athleisure wardrobe fashion EUCAsh Nak White Womens Shoes Size 8 M Flats MSRP $198Used Puma Basket Heart Womens (363073-02)White Patent Leather Size 8.5 , **Dockers 73639 Suede Moccasin Slippers, Men's Size XL (11/12), Brown (Repair)L.B. Evans Duke Scuff - Black - Mens , womens skechers 7.5 Beige Natural Ballet Style Walking Shoes comfy , 2017New Womens Pink/Army Green Satin Bow Walking Athletic Fashion Sneakers Shoes , Merrell Womens Riveter E-Mesh Castle Rock Running Shoes Size 8.5 (10810)Women's clarks womens shoes size 8 Outfall FlatsWomen's Tom’s Size 5 Ample Supply And Prompt Delivery Flats , Wmns Nike Lunarstelos Black Metallic Silver Anthracite White 844736 001Free People Size 38 8 Womens Calf Hair Varsity Gold Slip On Sneaker Slip On $128VANS TAZIE ESP MESH MARSHMELLOW WOMEN'S 5 SKATE SHOES /S85165.166Women's Converse All-Star Hi-Top Black/Red Rose Sneakers US 8Keds Women's Champion Seasonal Solids Silver 8 B(M) USLadies Size 8 Turquiose & Black Nike Sneakers ,
"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."