EARTH MOTHER : ELIXIR : RESEARCH HONOURS

WASHINGTON : The emergence of the Earth's first living organism billions of years ago may have been facilitated by a bolt out of the blue - or perhaps a quintillion of them.

Researchers said on Tuesday the lightning strikes during the first billion years after the planet's formation roughly 4.5 billion years ago may have freed up phosphorus required for the formation of biomolecules essential to life.

The study may offer insight into the origins of Earth's earliest microbial life - and potential extraterrestrial life on similar rocky planets. Phosphorus is a crucial part of the recipe for life. It makes up the phosphorus of DNA and RNA, hereditary material in living organisms, and represents an important component of cell membranes.

On early Earth, the chemical elements were locked inside insoluble minerals. Until now, it was widely thought that meteorites that bombarded early Earth were primarily responsible for the presence of ''bioavailable'' phosphorus.

Some meteorites contain the phosphorus called schreibersite, which is soluble in water, where life is thought to have formed.

When a bolt of lightning strikes the ground, it can create glassy rocks called fulgurites by superheating and sometimes vapourising surface rock, freeing phosphorus locked inside. As a result, those fulgurites can contain schreibersite.

The researchers estimated that the number of lightning strikes spanning between 4.5 billion and 3.5 billion years ago based on atmospheric composition at the time and calculated how much schreibersite could result.

The upper range was about a quintillion lightning strikes and the formation of upwards of 1 billion fulgurites annually.

Phosphorus minerals arising from lightning strikes eventually exceeded the amount from meteorites by about 3.5 billion years ago, roughly the age of the earliest known fossils widely accepted to be those microbes, they found.

''Lightning strikes, therefore, may have been a significant part of the emergence of life on Earth,'' said Benjamin Hess, a Yale University graduate student in earth and planetary sciences and lead author of the study published in the Journal Nature Communications.

''Unlike meteorite impacts which decrease exponentially through time, lightning strikes can occur at a maintained rate over a planet's history. This means that lightning strikes also maybe a very important mechanism for providing the phosphorus needed for the emergence of life on either Earth-like planets after meteorite impacts have become rare,'' Hess added.

The researchers examined an unusually large and pristine fulgurite sample formed when lightning struck the backyard of a home in Glen Ellyn, Illinois, outside Chicago. The sample illustrated that fulgurites harbor significant amounts of schreibersite. [Reuters]