The book has 8 riddles to solve!

Cy the cyanobacteria and Oxy the oxygen molecule are ready to take you on a trip back in time to the Great Oxidation Event.

Cy will help you learn interesting new facts about the world and Oxy is there to give you the definitions to new words.

Most of me is water but some of me is land

I am third from the sun

I weigh more than a tonne and

of the planets with life, I am the only one

What am I?

Answer: the planet Earth.

Earth is the third planet in our solar system. The Sun and its family of planets (Mercury, Mars, Earth, Venus, Jupiter, Saturn, Neptune and Uranus) formed when a cloud of dust and gas condensed 4.6 billion years ago.

I am a blanket but

You cannot use me

I make the weather for the planet,

And I'm held in place by gravity

What am I?

Answer: the atmosphere.

Volcanoes coughed gases into the air. These gases were kept high in the air by the Earth's gravity. This formed the early atmosphere. It was made up of methane, ammonia, neon, water vapour and carbon dioxide, and dust from meteors passing through the atmosphere. There was little or no free oxygen in the early atmosphere.

I wave but

I have no hand

I cover a lot of the planet

But I am not land

What am I?

Answer: the ocean.

Water vapour arrived in the atmosphere from ice in comets and gases that escaped the Earth's molten rock. After the Earth cooled down, the water vapour formed clouds. The clouds condensed and it rained for many centuries, filling up all the hollow basins in the Earth's surface, forming the early ocean.

Some call me a catastrophe

Free oxygen in the atmosphere was my birth

Written in my biography

Is a mass extinction on the Earth

What am I?

Answer: the Great Oxidation Event (GOE).

The GOE was the introduction of free oxygen into the atmosphere 2.4 billion years ago. This was because cyanobacteria and stromatolites made oxygen as waste. Oxygen reacted with dissolved iron in the ocean through oxidisation.

I belong to the phylum bacteria

I get my food through photosynthesis

The ocean is my utopia

And without me the Earth would be lifeless

What am I?

Answer: cyanobacteria.

Cyanobacteria first appeared around 2.7 billion years ago in the Archaean era. They are also called blue-green algae. They can use photosynthesis to make food and release free oxygen as a waste product.

I replenish the Earth's atmosphere

And I am the atomic gas number eight

You won't find me higher than the stratosphere

Trees excrete me when they metabolite

What am I?

Answer: oxygen.

Oxygen is a tasteless, colourless, odourless gas. The periodic table sorts the gases into a table, oxygen has the atomic number 8. Oxygen is the air that we breathe, without it there would be no aerobic organisms on Earth.

I am a process of reaction

Oxygen stole electrons from Fe,

It was this interaction

that made water rusty

What am I?

Answer: the process of oxidisation.

After cyanobacteria had introduced oxygen into the ocean, the oxygen reacted with the dissolved iron. This means that oxygen stole electrons from iron. While oxygen gathered electrons, the iron became oxidised. This created green rust in the ocean.

Evidence of the Great Oxidation Event:

The amount of oxygen in the atmosphere grew and grew. This changed the world from anoxic to oxic conditions. This event is sometimes called the Oxygen Catastrophe because it caused the extinction of anaerobic organisms.

Proof of this is found today in banded iron formations.

If you lived on Earth

But your species won't continue

You are likely on a path

That the dodo followed too

What am I?

Answer: extinction.

Organisms that couldn't survive in the new oxygen environment became extinct. Others managed to live in places with less oxygen. The high amount of oxygen in the atmosphere reduced the methane levels. This caused a glacial period called the Snowball Earth.

Even though the Earth froze over, there was still life that managed to survive. After the cyanobacteria came plants, fish and then the first four legged animals. The Earth had 5 major extinctions after the Great Oxidation Event and yet Earth continued until where we are today.

What do you think the future of the planet will hold?