Huygens rediscovers Titan

Abstract

The first analyses of data sent by the Huygens probe from Saturn's largest moon Titan are flooding in. They paint a picture of a ‘Peter Pan’ world — potentially like Earth, but with its development frozen at an early stage. The Huygens probe landed on Titan on 14 January this year, and seven papers published in this issue record the encounter. They describe a world that resembles a primitive Earth, complete with weather systems and geological activity. The ‘Huygens on Titan’ section opens with an overview of the descent and landing and a News and Views piece. Tomasko et al. describe the dry riverbed and drainage channels seen during Huygens' descent, evidence that liquid methane falls as rain or erupts from cryovolcanoes, periodically flooding the surface. This paper includes the images used on the cover to the Huygens section. Niemann et al. measured the abundances of isotopes of argon, nitrogen and carbon in the atmosphere, and conclude that there is no evidence that Titan's methane comes from biological activity. Fulchignoni et al. obtained precise measurements of temperature and pressure from the upper atmosphere right down to the surface. On the way down Huygens recorded evidence for lightning. Zarnecki et al. report that the probe landed on a relatively smooth surface of icy grains with the consistency of wet clay or sand. Isral et al. report that the aerosols in Titan's clouds have solid cores made from complex organic molecules containing carbon and nitrogen. And Bird et al. found that on average Titan's winds blow in the same direction as the moon rotates, and that close to the surface these winds are very weak, travelling at around walking speed.