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.Trotters Tan Suede Leather Strappy Sandals Sz.8.5M Women's Slip On ShoesMarc Jacobs Beige Bow Brown Patent Leather Cap Toe Ballet Flat Size 39 9 , Cole Haan womens brown leather slip on loafers mocassins size 7 , Old Beijing Cloth Embroidered Shoes Elegant blue , Clarks PRIVO Bronze Satin Leather Slip On Cross Strap Shoes Flats Women’s Size 7 , LifeStride Fantell Ballet Flat - Women's Size 7W NavyBrinley Co Womens ARO Faux Leather Wide Width Ankle Strap Round, Black, Size 9.0 , Pin Up Couture HEP26/BPU 1" Heel Black Faux Leather Wingtip Women's Oxford Shoes , CLARKS 60637 HALEY FALCON WOMEN'S BROWN SUEDE SNEAKERS SIZE 6.5 NEW IN BOX , Tory Burch Tasmin Espadrille Flats Floral Navy Blue Shoes Size 8PURE LEATHER MOJRI PUNJABI JUTTI FOR WOMEN BEST QUALITY , Dr. Martens Briar Black Velvet Shoes Size US 6 L Oxfords , lands end brown leather suede rubber sole slip on apres ski shoes 8 1/2 , Women Casual Outdoor Sneakers Fashion Comfortable High top Shoes Gray 4554_RCVince. Warner Brown Womens Shoes Size 8.5 M Flats MSRP $225New! Skechers Womens Equalizer-Vivid Dream Walking Shoes-Style 12028 73B la , Reebok Running Shoe, Women's Size 10, Grey/Yellow/CoralSalomon Womens 947362 Water Shoes Vented Contragrip Hiking 5.5 US Brown BlueSkechers Women's Go Walk Joy - Nirvana Slip-On ShoeSaucony Excursion TR10 Sneaker, Men's Size 11, BlackNew Womens Nike Lunarepic FK Shield Gyakusou 859890 400 , Himalayan Cat Print Running Shoes For Women-Free Shipping , Skechers BOBS Women's Squad - Photo Frame Sneaker, - Choose SZ/Color , New Balance Men's 300v1 Sneaker, Silver Mink/Sea Salt, 4 D US , Saucony Womens Sneakers Size 8 Black Purple Redeemer ISO Running New In BoxNIB Columbia Women's ATS Trail LF92 Outdry Hiking Shoe - size 9.5 - retail $85 , Nike Womens Air Huarache Run Ultra Print B/W Running Shoes 5 Medium (B,M) 1590PUMA LILLEA 2 (351346 12) LADIES SHOES / SNEAKERS BLACK/WHITE/ BLUE US SIZESMizuno Wave Rider 17 Running Training Sz W 9.5 White Gray Purple Womens 1A1Women’s Mephisto Rush Brown Tumbled Leather Walking Shoes size 6 M Portugal
"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."