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Fool’s Gold: The Search for Early Life

Michaela Partridge examining a banded iron formation from the Archean.

Michaela Partridge in the Pilbara examining a banded iron formation from the Archean.

By Michaela Partridge

The golden mineral, pyrite, is a valuable tool in the search for the secrets of early life on Earth.

Michaela Partridge is completing her PhD in astrobiology at the University of Queensland.

The full text of this article can be purchased from Informit.

Imagine a planet where the atmosphere is a hazy methane greenhouse and the surface is barely warmed by a faint young star that is only two-thirds as bright as the Sun we know today. An alien world with anoxic oceans full of microscopic life forms, most of which would perish in the oxygen-rich atmosphere that we depend on for our survival.

This planet is not separated from ours by the vastness of space, but by time. It is the Archean Earth. The Archean represents the first two billion or so years in Earth’s history, up until we start to see evidence of widespread atmospheric oxygen in the rock record 2.5 billion years ago. The composition of Earth’s modern atmosphere is a hot topic these days, but how do we learn about what the atmosphere was like in Earth’s deep past?

In the ancient rock record, all the available information about the complexity and diversity of the biosphere, the oceans and the atmosphere – from above the clouds to below the sea floor – is all squashed into one big rock pancake, so trying to fully reconstruct the early oceans and atmosphere is a tricky business. There are few preserved remnants of very ancient organisms so we have little direct evidence of these early life forms, but we can see the effect that ancient organisms had on their habitats.

We can study this effect on the chemistry of Archean rocks and minerals to determine...

The full text of this article can be purchased from Informit.