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.1a BASS BROWN LEATHER LOAFERS WOMENS 6 MMudpies Size Medium NWT Adults Size Lilly Pink and orangeWomens Bm Bernie Mev Crystal Black Wedges Womens Size 41 US 10.5-11 Sandals , Earth Couture Alena Women 8.5 Black Leather Platform Flats ShoesWomen’s Orthaheel Mae Brown Leather Shoes, Size 8 US Euro 39BORN Womans Leather Red Loafers Flatsles p'tites bombes ballerines EMMA Brush bleu P39 neuves Aut/Hiv 2018/2019 , stuart weitzman rootbeer cobrette feulchain shoe size 6 , Delman Womens Ballet Flats Size 7.5 Brown Leather Studded Pointed Toe Slip OnLadies Clarks Flats Style - Ordell Becca , inov-8 f-lite 195 - US8.5 WomensLauren Ralph Lauren Janis II Cotton Mesh women's sneakers US 6.5, B, Navy $44.00 , Vintage 1999 Tweety Bird Looney Tunes Denim Cotton Sneakers Blue Womens Sz 8women's pointy toes ankle strap Mary Janes shoes pointy toes stilettos wedding , Dr. Doc Martens 3A78 Air Chunky Brown Monk Strap Oxfords Women's US 8L.B. Evans Atlin - Brown - Mens , ASICS Neon Pink Ice Blue Asics Running Shoes Sz 9 , Reebok White Navy Light Blue Walking Shoes DMX Max Womens Size 10 , Converse All Star Black/White Canvas Slip On Tennis Shoes Women's Size 8 , Cape Clogs 42 Leather Wooden Open-Back Clogs Shoes Sweden Apples , BATA WOMENS BROWN SUEDE WALKER ATHLETIC SNEAKER SHOE SIZE 9.5 M , Womens NIKE ACORRA RFLCT Hi Top Black Leather Boots 807151 010 RRP .99Easy Street Women's Spontaneous Comfort Slip-OnNEW Under Armour UA WDRIFT RN MINERAL 1288065-002 Size 6 , NIKE WMNS WOMEN'S ROSHE ONE KJCRD 705217-301 JACQUARD MALT GREEN EMERALD SZ: 7 , New balance 456 White woman ortholite comfort Insole Size 10FILA Escalight Running Training Athletic Fitness Shoes Sneakers Pink Blue WomensSkechers EZ Flex 2 Cuddled Up Slip On Charcoal Comfort Shoes [152K]Skechers DLites This Just in Womens Sneakers 7- Select SZ/Color. , Skechers Flex Appeal 2.0 New Image Women's Slip-On Shoes Sneakers Gray 7M
"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."