Blow to hopes for life on Mars

Organic molecules found on rocks from Mars may not be the remnants of ancient Martian microbes after all, say researchers in the US and Norway. The team have shown the molecules could have been produced by geochemical processes - a finding which suggests many other planets in the solar system and beyond could be capable of manufacturing molecules needed for life. 

Scientists have long puzzled over how hydrocarbons arose in Martian meteorites found on Earth - postulating that they were a sign that life once existed on the Red Planet, or were imported from other meteorites striking Mars.   

Now, Andrew Steele of the Carnegie Institution in Washington, DC and colleagues have compared the geochemical characteristics of a 4-billion-year-old Martian meteorite with similar volcanic rocks found in the Arctic - and showed that they both contain the same tell-tale structures and molecular fingerprints. 

Using a range of imaging techniques coupled with Raman spectroscopy, Steele’s team compared Allan Hills 84001, a Martian meteorite discovered in the Antarctic in 1984, with volcanic rock from the Svalbard archipelago north of Norway. 

Both rock samples contain small globules of carbonate minerals, in which the organic molecules reside, in close contact with the iron oxide magnetite. 

’What seems to happen in both cases is that hot liquid rich in carbon dioxide from beneath the surface erupts, where it is rapidly cooled,’ Steele told Chemistry World. ’As the carbon dioxide cools in the presence of water on the surface, magnetite can catalyse the formation of polyaromatic hydrocarbons. 

’This is the first study to show that Mars is capable of forming organic compounds,’ he added. ’This observation does not exclude the possibility of life on Mars, but equally it shows that there is an abiological explanation for these molecules.’ 

Commenting on the research, NASA astrobiologist John Rummel told Chemistry World, ’This is a great demonstration of what an insightful interdisciplinary team can do to both explain previous discoveries and to extend their interpretation more widely. Clearly, the abiotic production of organics and carbonates is something that could be part of rocky, even mildly volcanic planets wherever they are found - and that may mean that the organics associated with life on Earth could be found all over this, and other solar systems.’ 

Simon Hadlington