The Schumann resonance on Titan (Cassini-Huygens)

Titan, the largest moon of Saturn, is the only extraterrestrial body for which we have direct in-situ measurement in the ELF band. During its descent through the dense nitrogen-methane atmosphere and after landing in 2005, the Huygens probe (part of the Cassini-Huygens mission) recorded an unusual ELF signature.

The interpretation of this signal is a matter of debate. Unlike on Earth, it is not clear for Titan what forms the lower conductive boundary of the cavity: it is being considered whether it is not a subsurface conductive ocean (for example a salty water layer beneath an icy crust), which would close the resonance cavity from below. In this Titan differs from the terrestrial model, where the floor of the cavity is formed by the conductive Earth's surface. Model calculations of Titan's resonance parameters (together with Mars and Venus) were carried out by Yang 2006.

Titan is thus the strongest evidence to date that the concept of cavity resonance is meaningful to apply even beyond Earth — even though the exact origin of the measured ELF signature remains open.