Huygens sent back 350 images and a wealth of radiometric and meteorological data on Titan. It showed that Titan’s atmosphere contains a number of chemicals based on carbon and hydrogen—basic building blocks for more complex organic molecules. It has strong winds, vigorous weather and storm activity, and thunder and lightning. There are clouds and rain—not of water, but of liquid hydrocarbons (natural gas).

Huygens’s cameras revealed an amazing variety of geological history on Titan, including free-flowing liquid hydrocarbons on the surface. When Huygens landed on the surface of Titan, it hit a thin, brittle crust. Underneath that broken surface was a sandy, swampy substance, which released wisps of methane gas when the probe’s impact heated it up. The temperature at ground level was –290 degrees Fahrenheit (–180 degrees Celsius), and the soil consisted mostly of dirty water ice and methane/ethane ice. Pictures of the ground around the landing site showed a surface that looked like a dry riverbed, strewn with smoothed rocks and pebbles.