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.New Womens Slippers Faux Fur Slip On Chain Diamante Shoes Casual Flip Flops , Grey Black Ballet Flats Size 9.5 M Womens SO Kohls Brand NWOB , Land’s End Womens Navy Slip on Outdoor shoes 53592 Size 8.5 B , CLARKS Womens GENETTE FROLIC Black Leather Side Zip Clog US 6.5MWomen's Brown Leather TEVA "SHAY" Slip-on Oxfords/ Sz 9/ Good Preowned Condition , Born Women's 8 1/2 M/W Brown Leather Clogs Mules Slides Fall and Winter B6398LL Bean Brown Patent Leather Duck Coastal Rain Skimmers Flats Womens 7 1/2 M , Trotters Womens Dark Brown Arianna Loafers Shoe Size 6.5 W , Gant Krista Satin slip on silver pink sale 16578396Women's FOOTPRINTS Birkenstock Mary Janes Leather Shoes Size 8 (38) Brown , ZARA BLACK FLAT BALLERINAS SHOES SIZE UK5/EUR38/US7.5Women Casual Stars Sneakers Fashion Comfortable High top Shoes White 4553_mC , SAS 8 Narrow Brown Slip On Women's ShoesVANS SLIP ON ( MAY 130X ) Pebble Snake Chili Pepper Women's Size 5.0 Skate ShoesNike Flex Run Womens Running Shoe Black 8 , Vince Camuto Womens bayana Leather Low Top Slip On Fashion, Black, Size 10.0 HGrNaturalizer Womens Saban Leather Closed Toe Loafers, Black, Size 7.5 MZ6iNew! Women's Skechers 22692 EZ Flex 2- Joy Ride Slip-Ons Natural A32Nice pair of Women's Gray Teal Merrell Barefoot Running Shoes size 7NEW BALANCE Women's Running Shoes, 11M WR400SWP Silver-Wht-Purple. NICE! , ☆Nike AirMax International Athletic Running/Walking Shoes WHITE US(6.5) Women's☆ , NikeCortez Leather Shoe Sz 5 Women's White//Varsity Red-Royal , Zamberlan Women Airound Gore-Tex? RR Hiking Shoes Waterproof 9.5 , ASICS Women's Jolt glacier grey Aqua Splash white T7K8N-9667 Size 7.0 to 11 , Nike Air Zoom 90 IT Golf Shoes Rory McIlroy 844648-001 Womens Size 8 Black White , Burberry Trainers Size Canvas Suede Leather Sneakers BeigeSkechers 15100 Womens Go Run Fast Cross Training- Choose SZ/Color.ASICS Gel-Fit YUI Cross Training Shoe-Women's 7.5,Indigo Blue/Glacier Sea/Silver , Puma Platform Lux - Red - Womens , FILA KAMEO 2 NEW W TAGS Training Shoes Size W M 9.5 ,
"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."