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.Paprika Gazell Dark Penny Women's Slide On Fur Lined LoaferCole Haan Women's Sz. 7 1/2AA (See Measurements) Brown & Black Tassel Shoes EUCSoftspots black leather women's slip on Mary Janes wedge loafer shoes SZ 8 WClarks Womens Black Patent Leather Loafers Croc Print Sz US 8.5 , Eastland Falmouth Shoes Loafers Sz 9 M Brown Leather Oxford Tie Womens 2C2 , Rockport Womens Sz 8.5 Loafers Slides Casual slip on Shoes Green Leather( B2) , STUART WEITZMAN FOR RUSSELL & BROMLEY BLACK PATENT LEATHER LOAFERS HEELS SZ 7.5New Sperry Top-Sider Firefish Stripe Multi Tan Leather Boat shoe/ STS98192 $80 , Easy Spirit Ezmae Dark Gray Mule Slide Shoes comfortable Nice $89 6.5CLOGS BY KLOGS EURO WOMEN'S SHOES COFFEE 8MSanuk Womens Yoga Ballet Sidewalk Surfers SZ 08- Pick SZ/Color.Womens C9 by Champion Black Pink Cushion Fit Running Sneakers Shoes Size 11 NewWomens Leather Pointy toe Ballet Flats Slip on Loafers Mary Janes Creepers Shoes , LADIES SHOES/FOOTWEAR - Step On Air Supafly white/silver open weave shoe , Anne Klein iflex Womens leather Loafer Shoes purple size 6M Akevolved casualBandolino Women's Hudson Oxfords Dark Green Leather Size 6.5 M , Steve Madden Hilda Black Low Top Women Shoes Size 10 M AL4401 , SANUK RUNAROUND ROSIE BLUE CHAMBRAY SLIP ON VEGAN SANDAL US 7 / / , Eric Meyer Medium Design Leather Retro Sneakers US Ladies 8.5 Navy, Bone *NEW* , Women's Womens mesh nike shoes Durability Athletic Shoes , NIKE Womens Nike Ultra Comfort Slide 882695-800 BRIGHT MANGO Size 5Saucony Kinvara 8 Navy Purple Running Shoe 10356-4 Womens Sz 7.5 NewWOMEN'S/JUNIOR SHOES SNEAKERS ADIDAS CF RACER TR K [AQ1676]HARRY POTTER INSPIRED CUSTOM HAND PAINTED HIGH TOPS MADE TO ORDER , ASICS Womens - DivaBlue/Silver/Orchid Running Shoes Size 8 (361387)NEW Women's Nike Dualtone Racer Light Bone/Black-White 917682-004 Size 8 RunningVans Women Sk8-Hi Slim - Leather Polka Dots white VN018IHUK , Nike Free 5.0 womens ladies blue green black athletic running sneakers shoes 6.5 , Skechers Women's Reggae Fest-Marlin-Fisherman Open Back Mule, Black, Size 10.0 x , PUMA Basket Mid Women's Natural Vachetta/Team Gold 36421302 Sz 6.5
"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."