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.Covington Tan Leather Comfort Loafer Shoes Size 9.5M , NIB Jacques Levine LAURA Raffia Red Belgian Flats - Size 7 , dimmi Women's Stretch Flat,Orange Weave,5.5 M US , LADIES WOMENS SKATERS TRAINERS FLAT SLIP ON PLIM SOLL SCHOOL PUMPS SHOES SIZE , BOC Born White Floral Flats Flower Slip On Size 6 / 36.5 MNib GUESS Xia Shoes Flats Suede Red Pony hair cap toe Cap US 6.5, , Women's Sandals Rialto Brown Leather Sling Back Size 7 MSPERRY WOMENS CREST VIBE LINEN LIGHT PURPLE SIZE 11TORY BURCH Womens Black Gold Logo Soft Patent Leather Flat Shoes sz 7.5M , Wanted Mercedes Sequenced Dressy Ballet Flats Choose Sz/ColorAlfani Women's Glenda Flat (6, Leopard) , New Grasshoppers Womens Janey Ii BlackLeather Fashion Shoes Size 7 , VANS CAMDEN HI ZIP WILD DOVE WOMENS SIZE 7 , **Reef- Walled Low Sneaker, Women's Size 8.5, Grey Tie Dye , Warm Slippers Thick Winter Slipper Home Indoor Flat With Sneaker Plush For Kicks , Converse Jack Purcell Womens Shoes Size 4.5 Gray Color Block Low Top SneakersCONVERSE One Star Sneakers Silver Sequins Womens Sz 9.5 SC8 , Converse All Star red and white stars sneakers. Women's 11Shape Ups Skechers Sneaker Shoes US 9.5 Women Leather White Silver , Women's Ellie Women's Coco-850 Moderate Price Athletic ShoesWomen's air jordan 1 retro High Quality And Inexpensive Athletic ShoesCLARKS GRASP CHIME WIDE BLACK 26066726 W WOMENS US SIZESSHIHWEISPORT ASICS T3N7N-9135 KAYANO 20 RUNNING SHOE FOR WOMAN *FINAL SALE* , Melissa Women's Love System Sneakers (Size 10) , MUST SEE FABULOUS 2016 $89.99 NEW BALANCE W530AB RUNNING SHOE WOMEN 11 B EEUC LN , PUMA Womens Ignite Xt Filtered WNS Running Shoe- Pick SZ/Color.Nike Free RN 2017 GS Womens Youth Junior Running Shoes Sneakers Pick 1 , Clarks Outdoor Womens Rock Training Purple Black Nubuck Shoes size 7 M , Women's ASICS GT-2170 Running Cross Training Shoes Size 7.5 (T256N) (W-137) , WMNS NIKE AIR MAX THEA PINNACLE BLUE size US 10.5 839611-400 ,
"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."