The most remote object yet touched by the work of human hands is Titan, the largest moon of Saturn. That contact came 10 years ago today, when a probe known as Huygens parachuted through Titan’s thick atmosphere onto its frozen surface. Titan is one of the most intriguing worlds in the solar system. Its atmosphere is made mainly of nitrogen, like Earth’s, but it’s far denser than Earth’s. It’s topped by an orange “smog” of organic compounds. And methane and ethane form clouds, and fill lakes around Titan’s poles. This mixture could resemble the conditions on the early Earth, so studying Titan could tell us about our own planet’s past. Huygens was built by the European Space Agency. It “hitchhiked” to Titan with the Cassini spacecraft, which is still orbiting Saturn today. Huygens used parachutes to lower itself to the surface — a ride that took more than two hours. During that time, it found that the smog atop Titan’s atmosphere extends down to within about 20 miles of the surface. It
