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Carbon Worlds

Graphite-black planets with diamond mantles.

When carbon outweighs oxygen, a planet's whole mineralogy flips: instead of silicate rock it builds graphite plains, carbide ridges, and - under pressure - a mantle of diamond. Astronomers predict them around carbon-rich stars (55 Cancri e is the famous candidate). They form water-poor and lifeless, but few worlds glitter like a coal-black planet under a close sun. Build one by pushing carbon past oxygen on a rocky recipe.

See all carbon worlds on Explore

A dark ringed planet hanging over the horizon of a rocky moon, its rings lit by a distant sun

New: Stand on Your Moons 🌒

A planet's surface view isn't the only ground any more. Press the surface button on a planet with moons and it asks where to stand: the planet itself, or any moon still in orbit, each tagged with what it became — ocean, ice, carbon, volcanic. Every moon gets its own ground and sky from its own physics: airless rock under a black sky, ice cracked by geysers over a hidden sea, sulfur plains shaking with eruptions, or orange haze you can't see the sun through. And hanging over the horizon, there's the planet you built.

Create your free account

Enter your email and we'll send a 6-digit code — no password needed.
We only keep your email and the username you choose. We never share or sell your email, and we don't send marketing — we use it only to email you a sign-in code. Read our privacy policy.

Send feedback

We're still building out the best experience we can — and we'd love your input. Tell us about features you enjoy, ideas you'd like to see, or pain points where something feels off, and we'll know where to look next.

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