Titan Wider Than Mercury, Second‑Largest Moon After Ganymede

Saturn’s moon Titan, about 5,150 km across, is wider than Mercury and is the Solar System’s second-biggest moon after Jupiter’s Ganymede, though its mass is only about 40% of Mercury’s due to its icy composition. Titan also boasts a thick nitrogen atmosphere and stable surface liquids (methane/ethane) with Earth-like features such as rivers and lakes, highlighting how size and nature can diverge: a world that looks planet-like but remains a moon. The distinction is orbital, not dimensional, and missions like Cassini–Huygens and the future Dragonfly continue to study Titan’s unique geology and weather.