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.Women Casual Loafers Chinese Hollow Out Slip On Canvas Cloth Shoes Flats Pumps , ANNE KLEIN iFLEX WOMENS Slides Leather Black 7Medium 1"Heels , Adam Tucker ME TOO Women's Perforated Taupe Slip On Loafers Shoes Flats Sz 10BELLA VITA WOMEN'S BLACK LEATHER OPHELIA FLATS - NWOB -NEW SHOES-NICE! 8WW , Wanted Olivia Scalloped Ballet Flats, Nude, 5.5 US / 35.5 EUSperry Top-Sider High Top Boot~Gray Corduroy-Plaid~Sequin Sneakers Shoes~Sz 6.5Easy Street Women's Delilah Fashion Sneaker, Grey Leather/Fabric, 5 M US , Skechers Womens Reggae Fest-Trail Dame-Scalloped Collar- Select SZ/Color.Dr. Scholl's Madison Slip-On Shoe - Women's Size 7 M, Navy BlueSkechers BOBS from Women's Plush Lite-Bobbles and Bits Flat Black/Multi 5 M US , callisto Lyra D'Orsay Ballet Flats 472, Black, 5.5 USGentle Souls 8.5 Black Suede Perforated Erica Slip On Loafer Skimmer Flat $198 , **Skechers Relaxed Fit Style Source Athletic Shoes - Women's Size 8 - Gray/PinkComfort Women Low heel Open toe Hollow out Back zip Roman College Shopping shoes , Mens Slippers House Shoes Black Corduroy Moccasin Slip On Indoor Outdoor ComfortNike Women's Zoom RS + Running Shoe Size 7.5Under Armour Womens Glyde St Black Charged Cleats Shoes 6 Medium (B,M) BHFO 3784 , EUC Oboz Luna Women's Mineral Blue Low Hiking Shoe Size 11 Retail $125Women's TAHARI Ballet Flats Shoes Trendy FlatsWOMENS REEBOK CL LEATHER SHMR in colors METEORITE / WHITE / ROSE GOLD SIZE 7.5 , Mizuno Wave Rider 17 Running Training Orange Purple Sneakers Shoes Womens 7.5Nike Girl's Flex Supreme TR 5 Athletic ShoeAltra Footwear Provision 3.5 Running Shoes-Women's size 8.5 GreyAdidas Originals Gazelle GS Trainers in Black & Grey in All SizesAsics Black And Pink Shoes Size 7 , Vlado Footwear Shoes Siren Fashion Women Black New , adidas Campus - Beige - WomensPuma Repli Cat II Sneakers Women's sz 6 WhiteVaporous/Gray/ AngelBlue (30184410) , Rocket Dog Porter Undercover Boot Women's Shoes Size , Merrell Continuum Pulse II Wintergreen Women’s Hiking Shoes Size 10 ,
"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."