You have probably seen the images of the surface of Mars, beamed back by NASA’s rovers. What if there were a time machine capable of roaming Earth during its remote geological past, perhaps even going right back to its beginnings, beaming back pictures of similar quality?

This is not science fiction. In remote corners of the world, geologists have found tiny relics of Earth’s very ancient surface.

I have been part of this scientific endeavour, looking at the treasure trove of information in the bedrock of the Makhonjwa Mountains in South Africa and the adjacent small kingdom of Eswatini.

These rocks reach back more than three quarters of the way through our planet’s long history of nearly 4.6 billion years. In my new book, The Oldest Rocks on Earth, I describe the graphic images “beamed back” by this geological time machine.

The ancient rocks reveal a world with extensive oceans and intense volcanic activity on the sea floor.

Deep beneath the crust, Earth was much hotter than today, giving rise to an unusual white-hot magma, rich in elements from its interior. Huge volumes of super-heated water........

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