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.Womens Born Sitton Slip On Comfort Shoes MNJ1 Size 6 , Womens Klogs Brown Leather Single Strap Shoes Size 7.5 EUCVince Camuto Womens Hadia Taupe D'Orsay Flats Shoes 5.5 Medium (B,M) BHFO 2987 , Born Boc ' Womens Penny Loafer Flats size 7M Blackbriana-09 Slip On Casual Party Ballet Flat Office Oxford Women Shoes White 6.5Cole Haan Brown Leather Moccasins 10B , RITZY 44! Qupid Women's Metal Chain Slip On Ballet Flats in BlackDEMONIA CRE605/BS Women's Black Suede Skull Buckle Creepers Gothic Punk Shoes , BIG SALE DEMONIA CRE400/BS/FUR Women's Leopard Punk Gothic Casual Creeper ShoesChie Mihara Reina Dark Purple Suede Floral Applique Ballet Flat, Size 36 , Dansko Professional Clog - Women's Size 12W Brown , MIA Zoe Denim Slip On Shoes, Women's Size 8.5, Blue NEW , New Women's Puma Running Shoes EcoOrtholite Gray & Turquoise 6 1/2Iron Fist Aloha Bitches Women's Pink Tropical Vegan Sneakers - US 6 , VANS. Women's or Men's CAMRYN Slim Casual Canvas HI Shoes. GREY. Womens US 11.new Converse Chuck Taylor All Star 11243/f gray heart low Men 7 Wo 9 , Lands End Womens 9B Tan Nubuck Suede Sneakers SC , Skechers Go Walk Slip On Sneakers-Women's size 8.5 GrayNew Balance Womens WW411WT2 Walking Shoe, White, 11 B USASICS Womens S755n Black/Silver/White Walking Shoes Size 7.5 (24196) , Reebok Yellow Sneakers For Ladies Sz 6.5, New Msrp $120 Super Cute! , NIB Merrell Outright Edge Waterproof Hiking Boot size 11 Med msrp 130.Women New Balance 1980 Classic Fresh Foam Zante Running Shoes Purple WL1980UCConverse Chuck Taylor Ox Neon Floral Casual Sneakers Women's Size 5 , Steve Madden Women's FROST Mule Sneakers. , Chaco Womens Outcross EVO MJ Athletic Support Outdoor Water Shoes Size 11 , New Womens New Balance 450v3 Running Shoes Style w450gv3 Gray/Blue 129C sr , Skechers Women's Memory Foam Vaso Tres Black 49935/BLK , Nike flyknit running shoes size 38. , Vans Skate Board Rose Black Gray & White High Top Shoes Sz 5.5 womens / 4 mens ,
"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."