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.BCBG Maxazria Banknote Calf / Shine Black 39 Women's Size 8.5 Narrow , Alfani Womens Gwennevah Closed Toe Ballet Flats, Black, Size 5.0Ladies Spot On Casual Brogue ShoesWomen ballet flat faux leather dress fashion rhinestone shoes SIZE:5.5-10 GA24Florsheim Toddler's Kearney Jr. Suede Oxfords - Size 11 M, Tan , Women's Born W01269 Loafers Clogs Shoes Size 9M Beige Suede Shearling Lined D9 , Tommy Bahama Sky Blue Leather Slides Mules Loafers Women's US Shoes Size 9MPOE Power of Essentials Reesa Silver Strappy Slip-on Shoe 7.5 NEW , Betsy Johnson Fancy Shoes size 5 , Crocs Walu Mule Womens crocs Mule- Choose SZ/Color. , Nine West Womens Akeelah Suede Pointed Toe Flat- Pick SZ/Color. , Lucky Brand Womens EMMIE Fabric Closed Toe Ballet MultiColor/Brindle Size 7.5Spring Summer Women Fashion Flat Canvas Shoes White Board Shoes Casual Shoes , Funtasma Flat Ballet Blue Glitter Bow Accent STAR-16G/BLUMelissa Ultragirl Cinderella Shoes In Box Size 1 Jelly Butterfly , NEW WOMEN'S TEAMCHEER VITALITY WHITE CHEER SHOES FWCF807 SIZE 4.5See By Chloe Ballet Flat 8.5M Clara Shoe Scrunched Black Leather Italy 39 Loafer , Adidas Men Adilette Cloud-foam Slipper Shoes White Beach Slide Sandales AQ1702Womens FootJoy GreenJoys 48744P White Golf Shoes Size 8 MSkechers Performance Women's Go Walk 4 Majestic Walking Shoe , Women's Vans saumon oldschool 8,5 US Beautiful Athletic Shoes , PUMA Formlite S HY Black Women's Casual Sneakers 187334-07 , CONVERSE Women's Chuck Taylor All Star High Tops sz 6 Buff Beige White HiWomens Nike SF Air Force 1 Mid FIF Force is Female Vintage Wine SZ 6 AJ1698-600Brooks GTS 16 Edition Women's 9.5 Running Cross Athletic Shoe Gray Teal , Clarks 26120076N: Womens Narrow Black Sheep Leather Vendra Bloom WedgeNike Air Max Thea Ultra Running Shoes White leather sz 10 ladies , Women's Puma Prevail Heart Sneakers, New White Gold Sport Runinig Shoes Sz 7.5 , Sperry Top-Sider Womens Crest Vibe Flooded Ivory Slip-On Sneaker Shoes NIBPERFORMACE WOMEN'S GO WALK-GLITZ SLIP-ON WALKING SHOES SIZE 8.5
"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."