Age: 3-4 billion years old
Diameter: 10,000 – 15,000 km
Surface: rocky, mostly barren
Atmosphere: carbon dioxide, oxygen, nitrogen
Evolution: cools to class H, K, L, M, N O, P
Life forms: vegetation, simple organisms
Examples: Delta Vega
After the core of a class f planet is sufficiently cool, volcanic activity lessens and the planet is considered class G. Oxygen and nitrogen are present in some abundance in the atmosphere, giving rise to increasingly complex organisms such as primitive vegetation like algae, and animals similar to sponges and jellyfish. As the surface cools, a class g planet can evolve into a class H, K, L, M, N, O, or P class world.