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 Ladies Tassel Flat Shoe in Black Casual Canvas trainers Pumps Slip On Fla , REPORT FLAT COTTON BLUE SHOES SIZE 6 (S281) , Delman Beige Orange Striped Bow Design Ballet Flats Size 7Clarks Golden/Tan Leather Slip On Comfort Mules w/Stitched Design, sz 8.5M , SH16 Munro American 7.5N USA Brown Leather Embellished Monk Strap Loafer ShoesManolo Blahnik Womens Shoes Size 38.5, 8.5 Burgundy Loafers LeatherClarks Brand New Azelia Major Espadrilles Black Slip On Shoes Womens Size 9.5 WWomen Flat Heel Square Toe Shoes Slip On Comfort Loafers Patent Leisure Leather , UNIF Koop Spike Hot Pink Spike Platform Sneakers Punk Shoes Women's Size 10 New , Women's Van Eli Frankie Flats Sz 8.5W , Asics Gel Womens Sz 8.5 Rocket Shoes Sneakers K025 Blue Mesh Walk Hike Athletic , Eric Michael Olivia Slip On Shoes - Women's Size 10/11 - BlackLADIES SHOES/FOOTWEAR - SOA Sandal Amigo II black , Dansko BROWN SHOES WOMENS SIZE 38Ryka Studio Flex Mid White Sneakers Shoes Sz8/39 Womens Ortholite K1094WWS , RYKA Radiant Plus Walking Shoe SIZE 6 WIDE White/Pink - EXCELLENT w/box , KoziKicks Women's Ergonomic Comfort Non-Slip Sole Plush-Lined Active Slippers , ZELLA Pink Neon / Ocean Pebble Running Athletic Women’s Sneaker Shoes size 6.5Womens BROOKS Ghost 7 Pink Gold Running Shoes Size 7.5 US 38.5 UK BWomen's womens FLATS 1234 Queensland FlatsWomen's Chaussure Art Taille 36 Genuine Flats , Nike Studio Wrap 2 Print Women's Training Yoga Dance Shoe Black 641529 001 , Diane Von Furstenberg Budapest Satin SneakerNWOB Nike Women's Lunarglide H20 7 Flash Running Shoes 803567-500 Sz 6.5 Purple , Converse Women's Chuck Taylor All Star High Top Sneakers SANDLE zipper Size 6 , Women's Puma Burst Mesh Running Shoe Red Size 8.5 #NGHV7-201NEW Nike Air Zoom Pegasus 32 wmn's Size US 5.5 Running shoes 749344-500Nike Womens 880560 Silver Running Shoes Size 8 (24640)Saucony 3D Grid Hurricane 7 Women’s Size 7 Running Shoes Wht/Sil/Blu NIBAdidas Laser Cut Tennis Shoes Size 6
"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."