How are shells made?

Across the world beaches are littered with an amazing array of shells – some are spirals, some are long thin cones, others are long and thin like a razor, and one even has an amazing fractal pattern of spines. But where did they come from, and how were they made?

That’s the question from CrowdScience listener Tamsyn in Australia. Until recently she didn’t realise that shells were made by living creatures, and now she’s fascinated by how on earth they produce such an amazing range of patterns, colours and sizes.

Presenter Marnie Chesterton heads for the beach with a mussel expert to try and find an answer, discovering that shells are a protective armour made of calcium carbonate that suits each creature’s lifestyle. From elongated shells that bury into sediment to thick, robust shells on creatures that live on the open ocean, these marvellous molluscs build their shells like an inkjet printer on paper, building up patterns line by line.

Some creatures create such complex shapes and patterns that we need the help of mathematicians to work out how they’re made. Marnie heads for Oxford University to meet a pair of researchers who have spent the past 15 years deciphering the mathematical rules that molluscs follow. Armed with that knowledge, can Marnie create her own shell using nothing but her kettle?