Mars lost its magnetic shield 4 billion years ago, triggering slow atmospheric escape

Four billion years ago, Mars lost the invisible armor that had made it something like a living world — its magnetic field collapsed as its core cooled, and without that shield, the Sun slowly claimed the atmosphere that had once allowed liquid water to pool on the surface. The transformation was not a sudden catastrophe but a patient unraveling across geological time, leaving behind the frozen, airless desert we observe today. Mars now stands as both a warning and a laboratory, reminding us how deeply a planet's fate is tied to the hidden machinery of its interior.