A World That Lost Everything

Mars is a cautionary tale. Roughly 4 billion years ago, its magnetic field faded as the planet's internal dynamo shut down. Without that shield, the solar wind began stripping away the air. For hundreds of millions of years Mars clung to a thicker atmosphere and flowing water — possibly even conditions suitable for life — but the loss was relentless. By around 3.5 billion years ago the surface pressure had dropped so far that liquid water could no longer survive.

Today Mars has an atmosphere less than 1% as dense as Earth's, composed mostly of carbon dioxide. Surface temperatures average -60°C. The rusty red color comes from iron oxide — literal rust — coating the soil and rocks. Mars did not just die; it rusted to death.