Starship stands roughly as tall as a 40-storey building and carries more than 5,000 tonnes of liquid methane and oxygen. Methane was chosen partly because both propellants could theoretically be manufactured on Mars from atmospheric carbon dioxide and water ice—meaning its engines are designed to burn a return ticket whose ingredients may already be waiting there.

Starship stands roughly as tall as a 40-storey building and carries more than 5,000 tonnes of liquid methane and oxygen. Methane was chosen partly because both propellants could theoretically be manufactured on Mars from atmospheric carbon dioxide and water ice—meaning its engines are designed to burn a return ticket whose ingredients may already be waiting there.

Starship’s methane engines fit a Mars return architecture, but turning thin air and buried ice into cryogenic propellant would require a large autonomous factory.