In January 2005 a European probe named Huygens fell for two and a half hours through the orange haze of Titan and landed on a plain of ice — the most distant touchdown in history, and no spacecraft has ever gone back.

In January 2005 a European probe named Huygens fell for two and a half hours through the orange haze of Titan and landed on a plain of ice — the most distant touchdown in history, and no spacecraft has ever gone back.

Most probes orbit worlds or fly past them. In January 2005, Europe's Huygens did something far rarer: it landed. Carried across the solar system by NASA's Cassini, the probe separated, coasted in silence for three weeks, then fell for two and a half hours through the orange haze of Titan, Saturn's largest moon, before settling onto a plain of damp, sand-like ice. Its cameras revealed river channels, shorelines, and pebbles rounded by flowing liq…