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.TAHARI WOMENS SNAKE SKIN PRINT FLATS SHOES 6.5 WITH BUCKLE JULESAravon Women's Jodi Mary Jane Flat, Black Leather, 11 M US , TS shoes TAKING SHAPE sz 6 / 37 Paloma Pool Slide comfy easy wear slip-on NIB!Comfortable Womens Summer Flats Shoes Driving Loafers Slip on Pumps Stars Sandal , NEW SOFTWALK BLACK LEATHER SLIP ON COMFORT LOAFERS WEDGE SHOES 6 MDANSKO Women's Brown Leather Clog/Mule Slip-on US 6.5-7/ Slip resistant , Vivienne Westwood Rubber Jelly Flats SPACE LOVE BALLET PUMPS. Sz US 6 , BareTraps Nickle Black Leather Twist Detail Ballet Flat 6.5 NEWVionic SPARK MINNA Purple with snakeskin print detail orthaheel technology 8 W , Seychelles Olive Quake Ruffled Suede Pull on Sneakers Sz 11 NWOBles p'tites bombes ballerines EDEN vernis Wine P38 neuves Aut/Hiv 2018/2019PAIRE DE DR MARTENS POINTURE 41 OU 7 UK / BORDEAUX / BON ETAT , Womens Flats Blowfish Malibu Shoes in Shanghai Grey Choose Your SizeNew Grasshopper Ortholite Women's Shoes Sneaker Blue Size 9.5 WW ? , Breathable Round Toe Chunky Low Heel Buckle Leather Casual Women's Shoes Zhou8 , Dickies Athletic Slip-On - Black - WomensEmily the Strange Womens Mary Janes TUK Cat Face Size 8Womens Rivet Multi Color Breath Mesh Sneakers Wedge Hidden Sport ShoesPlus SZ us , Mens Fleece Lined Knitted Mule SlipperAsolo Hiking Blue Leather Women's 5.5 Hiking Shoe Boot Asolo Outdoor Euro38-2/3Super Fashion Womens Pull on Ankle Shoes Preppy Flats Elastic Woven Boots Shoes , Women's CHAMPION LEATHER RUNNING/ATHLETIC....SIZE: 7.5.........EXCELLENT CONDITION Great Varieties Athletic ShoesSam Edelman sneakers size 8.5 white pull on pom pom blue shoes low top WomensSkechers Women's Go Flex Max Strength Walking Black 7.5 B(M) USWomen's Mizuno Wave Lightning 7 Size 13-Black , ASICS Gel Resolution Tennis Shoes,E350Y, White, Womens US Size 7.5Brooks Launch 4 Shoes Women's Black/Purple/Blue/Pink Size 9 Custom Gel Inserts , Columbia Techlite Hiking Trail Womens Size 8 , Ryka Women's Sky Walking Shoe - Choose SZ/ColorReebok Southrange Run L Women's Running Sneakers Shoes Black/Pink/Silver/Blue
"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."