Introduction

Seismology of giant planets has long been considered as both a potentially powerful tool for probing their interiors and a natural extension of helioseismology. Giant planets are mostly fluid and convective, which makes their seismology much closer to that of solar-like stars than that of terrestrial planets. For this, we refer the reader to the introductory chapters about helio- and asteroseismology for basic concepts and vocabulary. By being the biggest and closest, Jupiter has attracted most of the efforts in this domain. Theoretical studies started in the late 1970s and the first observational attempts were undertaken in the late 1980s. So far, the two major results are a clear detection of acoustic oscillations of Jupiter (Gaulme et al., 2011), and the signature of Saturn f modes in the rings by the NASA Cassini spacecraft (Hedman and Nicholson, 2013).

This chapter first examines the theoretical motivation for developing seismology of giant planets, which mainly stands on an inaccurate knowledge of their interiors (Section 14.2). The next sections focus on two crucial points: why seismology can be done on giant planets (14.3), and what can it bring in terms of physics (14.4). We then present the observation techniques that have been used or envisioned to detect oscillations (14.5), and the main observational results (14.6).

Interior structure

Giant planets are planets massive enough to have retained the hydrogen and helium initially present in the circumstellar disk that led to the formation of the central star and its planets. The study of their composition is important in understanding both the mechanisms enabling their formation and the origins of planetary systems, in particular our own. Unfortunately, composition determination is complicated by the fact that their interiors are thought not to be homogeneous, so that spectroscopic determinations of atmospheric abundances are probably not representative of the planet as a whole.