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.STUART WEITZMAN Patent Leather Driving Buckle Bit Loafers 8B Made in Spain1635 RON WHITE Rita Houndstooth Slate Suede Water Resistant Penny Loafer 42 E , Aerosoles Women's Sidewalk Slip On Shoe, Black Suede, 7.5 M USSperry Top Sider 6.5 Boat Shoes Gray Suede Patent Y , KAREN SCOTT Soft Step RILEY Slip On Leather upper Bootie Heel 8.5 M DARK BROWNWOMENs LEATHER TAN SANDALs Sz 10 Med by HUNT CLUBFabulous "Luc Berjen" Brown Leather Pumps Flat Shoes NEWSOFFT Tan Brown Woven Leather Wedge Heel Comfort Strappy Sandal Women 9.5 M ShoePaul Green Patent Red Leather Peep Toe Flats / Short Pumps Size 5.5 (AG11)Unique Vis a Vie Mint Green Pearl Lamb Flat Mule Slide Rhinestone Buckle Size 10 , CARLOS SANTANA SHOES womens 6.5 Vegas Brown Suede 1007030 Peep Toe Flats SandalsBelle Sigerson Morrison Women's Black Leather Slip On Ballet Flats US Size 10**Easy Spirit Go Sport Fabric Slip On Sneakers, Women's Size 7.5 W, Blue , New Quiksilver Womens Aqys700027-Xswg Shoes Athletic Shoes Size 6WMNS NIKE AIR MAX 1 ULTRA ESSENTIALS DEEP ROYAL BLUE-PURPLE SZ 6 [704993-401] , Nike Hijack Mid Womens RRP NOW .99 TO CLEAR , Hot Fashion Women's Smart Casual Speedcross Outdoor Running Sports Shoes New , Vtg Vans metallic Purple womens shoes Unisex Men's 7.5 Women 9.0 SkateboardMARNI - BALLERINES - POINTURE 38 - CUIR - authentique , Via Spiga Womens Mercer Black Leather Fashion Sneaker Size 7.5 (22108)Womens 7 M MBT Barbara brown suede leather shoes toning walking comfort rockerNew Ryka Womens E2326m6 White/White Mules Size 8.5 (23523) , BRAND NEW $100 Nike Air Huarache Ultra Slip-On Sandal Black 885118-001 sz 5 9 12Brooks Ghost 9 Purple Pink Cactus Black Women's Size US 11 Running DNA , Oboz Women's Fuchsia Pika Low Hiking Shoe 11MSuperga Women's 2750 Polywool Sneaker, Grey, 7 M , Mizuno Wave Creation 17 (black/silver/pink) Women's Size 11New Women's Nike Blazer Spikeless Golf Shoes Sz 8.5 818730-400 Navy Blue/White , Marc Fisher Calie Brown Leopard Slip On Fashion Sneaker Shoe NEWNIKE Air Zoom Pegasus 34 Women's Running Shoes Size US 6 Hyper Turq/Blue OC04
"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."