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.Baretraps IMANI Black Womens Shoes Size 7.5 M Flats MSRP $59 , Talbots Women's Silver Perforated Peep Toe Slip On Ballet Flats US Size 8 B , q COLE HAAN BROWN LEATHER LOAFERS WOMENS 6.5 Mb.o.c BORN CONCEPTS BROWN SHOES WOMEN'S SIZE 8 MSPERRY TOP-SIDER Suede & Canvas Gray & Pink Argyle 2 Eye Boat Shoes Size 7 EUCNICOLE " SNIP " LEATHER SHOES SIZE 10 WHITE RED SNAP DECORATION FLATS SLIP ONSJellypop Women's Flats Glider 6.5M new w/out box Ribbon Toe, cushioned soleAhnu Jackie Pro - Go-anywhere Slip On Moc Toe Leather Loafers Olive Women's 10.5 , BORN Size 7 (38) M Brown Leather Bow-Detailed Low-Heel Ballet Flats Loafers , ADIDAS size 7 women's ballet flats split sole Prajna Gray/Blue shoes slip-on 7.5 , ALEGRIA Womens KELI Cosmic Multi Color Leather Loafers ; US 6-6.5 (KEL-753)Comfortiva Sallis Ballet Flats - Women's Size 8.5 M - Navy , Talbots nude closed toe sandals with roses on the the front, Sz 9 M.Antonio Melani Womens Leather Shoes Size 7.5 Blue Mary Jane Eyelets S04A4 , Womens Flats shoes Round toe Pearls Winter Fur Warm Loafers Casual Pumps 2019 , Arcopedico Blue Knit Slip On Shoes Womens Size 36 5.5-6 NewNike Air Womens Shoes Size 8.5 Walk Air Liner Max White , Breathable Sneakers Running Girls Women 's Fashion Shoes Sport Casual Shoes Sz# , Ryka Women's Regina Walking-Shoes, Blue/Purple/Silver, Size 6.0PRISTINE CONVERSE All-Star Navy Blue Women's Shoes Size 8 US with Original Box , WOMEN'S ASICS GEL GT 2150 RUNNING SHOES SZ 9 39.5 USED T054N GUC SNEAKERSWomen's Pink Puma Cell 10 Shoes Size 5 (W-117) , MERRELL WATERPROOF HIKING TRAIL SHOES GREAT COND WON 9 200G INSULATION , Adidas Originals Women's Stan Smith Mid Trainers Core BlackWomens Skechers Flex Appeal 2.0 Tropical Breeze Memory Foam Gym Trainers , adidas Athletics 24/7 Tr M Cross TrainerDiadora DA8AWJ6710 Black White Women Running Walking Casual Shoes Sneakers , Womens Nike Air Max Zero Sz 5 (857661 006) No Box , B0 NEW ASH Nikita Bis Camouflage Studded Fashion Athletic Sneaker Size 35 $155New Women's Skechers GOwalk 4 - Fascinate Walking Shoes (14914) (N6) 7 ,
"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."