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.Melissa + Campana Gold Zig Zag Jelly Shoes Flats Size 8Teenmix shoes Size 7 Cream Very Good Conditionwhitemt Womens Shoes Black PRETTI Slip On 6 1/2 Fleur de lis embellished , Bussola 39 Womens Black Leather Flats Walk Your Comfort Roll Up Ballet Bow Shoes , MIA DOCKTAILL BLACK SUEDE CAUSAL LOAFER SHOES 6 M Women's - New , Melissa + Jason Wu Space Love Ballet Flat - Rust Orange Size 8KEDS womens 8 navy blue white polka dot canvas sneakers shoes MINT , Bucketfeet Gold Focus Shoes Low Top Canvas Slip On Womens Size 5 Zachary Snyder , Women's Sperry Top-Sider Bahama Coral Jersey 2-Eye Moc Toe Boat Shoes Size 9 MEasy Spirit Womens Geinee Closed Toe Slide Flats Black Size 9.0Tory Burch flats patent leather ivory cream size 7.5Calvin Klein Womens Inca 2 White Fashion Sneakers Shoes 7 Medium (B,M) BHFO 2965 , Sketchers Women’s Sz 9.5 Gray Blue White Shape Ups Walking Toning Rocker Shoes , Qwaruba Sydney Sheepskin Slipper, Men's 8Avia A5018WWDL Women's Walking Shoes White w/ Silver Trim US 10,Burnetie Women's Fold- Low SneakerMizuno Wave Inspire 13 Womens Size 9.5 Running Shoes Blue Pink L702=738 Under Armour Women's SpeedForm Gemini 3 Graphic Running SIZE 10Woman's Mizuno Wave Ascend 4 Run Walk Shoe/sneaker Size 9Merrell Womens 9 M Mimosa Moc Boulder Beige Leather Walking Shoes Slip-On LoaferPONY SHE RUN '78 LOW SNEAKERS WOMEN SHOES NT SHDE/DEC CH 9938 SIZE 6.5 NEW , ADIDAS WOMENS RUNNING SHOE EDGE LUX CLIMA PINK WHITE SIZE 8 NEW ULTRA LIGHT , ZARA floor contrast Hoody US6,EU36 LightWeight black fashion sneaker 6720/101Capezio Dance Women's Jr. Footlight W - 550 Black Dance Shoes , Brooks Ravenna 8 Running Shoes, Women's Size 6 B, Navy/Purple/CoralNew Balance Q17 Strobe Women’s Pink Running Shoes Sz 9.5 #WSTROLP1 MSRP $80 EUCWomen's Reebok CrossFit Nano 5.0 POLAR BLUES/STEEL/BLACK Sneakers V67615 Size 6Nike Women's Darwin Casual Shoes NEW Light Iron Ore/Red Bronze , Hoka One One Womens Stinson Lite Sz 10M , Women's NIKE TANJUN RACER Hot Pink Running Shoes 921668 601 multiple sizes
"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."