UCL microfossil discovery generates major media interest

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Image of haematite tubes from the NSB hydrothermal vent deposits

Haematite tubes from the NSB hydrothermal vent deposits

Matthew Dodd

An international team led by UK scientists has unearthed the remains of microorganisms which are believed to be the Earth's oldest life forms.

The discovery of the tiny filaments and tubes which UCL researchers believe were formed by bacteria which lived on iron between 3,770 and 4,300 million years ago has generated intense media interest.

Matthew Dodd, a PhD student at UCL whose work has been supported by an Engineering and Physical Sciences Research Council (EPSRC) Doctoral Training Partnership (DTP), is first author of the study published in Nature. Alongside UCL and EPSRC, NASA and Carnegie of Canada also funded the study.

The study describes the discovery and analysis of the filaments and tubes that were encased in quartz layers in the Nuvvuagittuq Supracrustal Belt near Quebec, Canada, which contains some of the planet's oldest sedimentary rocks.

Mr Dodd, from UCL Earth Sciences and the London Centre for Nanotechnology, said: Our discovery supports the idea that life emerged from hot, seafloor vents shortly after planet Earth formed. This speedy appearance of life on Earth fits with other evidence of recently discovered 3,700 million year old sedimentary mounds that were shaped by microorganisms.

The team investigated whether the tubes and filaments, made of haematite - a form of iron oxide or 'rust' - could have been made through non-biological methods such as temperature and pressure changes during burial of the sediments, but found these possibilities unlikely.

The haematite structures have the same characteristic branching of iron-oxidising bacteria found near other hydrothermal vents today and were found alongside graphite and minerals like apatite and carbonate which are found in biological matter including bones and teeth and are frequently associated with fossils.

They also found that the mineralised fossils are associated with spheroidal structures that usually contain fossils in younger rocks, suggesting that the haematite most likely formed when bacteria that oxidised iron for energy were fossilised in the rock.

Study lead Dr Dominic Papineau, from UCL Earth Sciences and the London Centre for Nanotechnology, said: The structures are composed of the minerals expected to form from putrefaction, and have been well documented throughout the geological record, from the beginning until today. The fact we unearthed them from one of the oldest known rock formations, suggests we've found direct evidence of one of Earth's oldest life forms. This discovery helps us piece together the history of our planet and the remarkable life on it, and will help to identify traces of life elsewhere in the universe.

Reference: PN 15-17