How did Titan’s dunes form?

Abstract

On Saturn’s moon Titan, the lakes, seas, and rain are made not from water but from hydrocarbons. The moon even has hydrocarbon dunes, standing 100 m high. Until now, scientists have proposed that reactions in Titan’s atmosphere produced the dunes’ particles, but new laboratory experiments suggest that cosmic radiation interacting with acetylene ice on the moon’s surface could provide another explanation (Sci. Adv. 2019, DOI: 10.1126/sciadv.aaw5841). One clue that atmospheric reactions might not be the only source of the dune hydrocarbons: observations suggest that the dunes’ particles are more than 100 times as large as what atmospheric chemistry can produce. Ralf Kaiser and colleagues at the University of Hawaii, Manoa, decided to test an alternative origin with a lab experiment that simulates the effect of galactic cosmic radiation (GCR) on acetylene ices, which are thought to exist on Titan’s surface in the same areas as the dunes. GCR itself doesn’t