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.womens yellow box black sequin slip on mules shoes size 6 1/2 , CLARKS FERN GREEN SUEDE NUBUCK MULE HEEL SHOES 7 MIKRUSH Womens Jada Faux Suede PomPom Espadrille Slip OnsSLIGHTLY USED WOMEN'S SODA SIZE 9 ANIMAL PRINT FLATS GREAT CONDITIONWomen’s KEEN Bern Cush Boho Ankle Bracelet/Strap Flower Embossed Flat Shoes Sz 7 , naturalizer Saban Slip-On Loafers 131, Black, 6.5 N US , Born Black Leather Loafers Low Heel Leather Braid Strap Buckle Shoes Womens 7.5M , Donald J Pliner Womens Size 7 "Ezara" Black Mocc-Stitch Tassel Driving Loafers , Propet Twilight Black double strap mary janes 10 Wide D comfort walking shoesRialto Annalynne Ballet Flats 929, Black Patent, 7 US , Klogs Women's Clogs Display Model Shoes Polina Woodland Patent 7 MSperry Rosefish Textured Casual Boat Shoes - Women's Size 9 M - Linen/Rose , Giani Bernini Womens Jileese Square Toe Loafers New White268262 Size 5.5 , Clarks Candra Blush Flats - Women's Size 10 W, AubergineTrotters Women's Mila Goldwash Metallic Soft Nappa Leather Loafer 10 M (B)ECCO Sport Arizona Granite Green Slip On Comfort Shoes Size 36 / 5 - 5.5 M , XIN BEN Size 39 Beige Canvas Gym Basketball ShoesNew Balance MW966 Brown Leather Walking Athletic Shoes Size 8 M DJ-41 | Genesis | Women's Athletic Shoes | Size:9M Pre-Owned , Women's Skechers Go Step Lite Glitz - Charcoal - Width: med - Slip OnsWomen's Tory Burch Black Flats 10.5-11 Sale Price FlatsHeelys HE100034H Kids Propel Terry Sneakers, Navy/Blue - 8 , Women's Nike Air Relentless 6 Pure Platinum Racer Grey/Pink Size 5.5ADIDAS ORIGINALS SLEEK SERIES AGASHAE MID 36 36.5 NEW aditennis nizza top ten , Keen Women's Presidio Shoe - Black / Magnet - US size 9 "CLEAN"New Balance WT510 Sneaker - Women's Size 9.5B Gray/NavyNike Zoom Rival D III Plus Womens Track Shoe 11 USA Black WHITE , ADIDAS WOMEN TERREX VOYAGER CW CP W - SIZE 10 , Nike Lunareclipse+ 2 Breathe Pure/Platinum-White 511493-010 Women's SZ 1135 40 height increasing shoes platform lady heel inside black red zapato alto ,
"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."