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.X51 Paul Green Kianna Black Patent Penny Loafers Shoes Women Size US 6 Mflip flops shoes slippers flowery fabric summer red white ladies light slip on , Etienne Aigner Pretty Black Ballerina Shoes Flats W/ Bow Size US 7 M , Women's G. H. Bass Co. Brown Woven Leather Casual Slip-on Flat Shoe - Size 5MVeretti Womens Leather Loafers Flats Black Slip On Laser Cut Size 36 US 6 NWOT , Crocs Womens Eve Ballet Flat- Select SZ/Color. , SAS Womens Loafers Slip Ons 8.5 Narrow Black Heels Very Good Tripad Comfort Foot , Mt. Emey 618 - Women's Lycra Casual Diabetic/Orthopedic Shoes by Apis Size 7.5 , Dansko Womens Mary Jane Brown Shoes 40 Size 9 SC8 , Rieker Antistress Doris Slip On Shoe - Women's Size 8, Brown , Bernie Mev DREW-001 bernie mev. Womens Drew Loafer 41 (US ) MWomen's Converse Chuck Taylor One Star Gray Sparkle Sequin Sneaker Size 6 , Nine West Women's SHIREENE Fabric Loafer Flat - Choose SZ/ColorAlegria by PG Lite Silver Petal Ballet Flats Women's Size 6 Pewter Dazzle $119 , VGUC Superga Dahlia 2750 Cotu Classic Sneaker SZ 40 / 9 US WMN Purple 7 Big KidsNew!?Women's Skechers Relaxed Fit - Breathe Easy Spectacular 22531 Navy 129M pmChristmas Snowflake Women Running Shoes Shock Absorbing Smart Sport Walking ShoeSperry Top-Sider Fashion Sneakers Gray Textile Women8.5Medium (B, M) , RARE NIKE Air Zoom Terra Kiger 2 Fuchsia Pink Running Shoes Sneakers Womens Sz 8Vans Off the Wall Womens Surf Chauffette STV Navy White Boat Shoes 5.5 CanvasReport Women's Albie Sneaker, Nude, Size 6.5Skechers Women's On The Go Vulc 2 Ankle-High Tennis Shoe , NEW $69 Womens Saucony Grid Seeker running shoes, size 11Womens Fred Perry Clarence Leather Quilted Canvas Size US 9Nike Women's Roshe One Winter Running Shoes Black/Black-Sail 685286-001 Sz 7.5 , Nike Women's Free RN Running 831509 006 Dark Grey/Black/Cool Grey/Pink Sz 9A455G Nike Womens Air Huarache Run 634835-014 Size 6 NEW , ECCO Soft 8 Sneaker - Women's Size US:7-7.5 / EU:38, Black** Brand New ** Women's New Balance Running Shoes W780BR4 780v4 W780 780Nice Blue Silver White BROOKS Adrenaline 11 Running Shoes US Sz 9B
"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."