[P-PS01] Outer Solar System Exploration Today, and Tomorrow

[PPS01-P09] Reorientation of Ganymede induced by furrow-forming impact

*Naoyuki Hirata¹ (1.Kobe University)

Keywords:Ganymede, impact, reorientation(true polar wander)

Ganymede, the largest satellite of Jupiter, has a global concentric system of tectonic troughs. The trough system, so-called furrows, is the oldest recognizable surface feature on Ganymede and the largest impact structure identified so far in the solar system, created by an impactor with a radius of ~150 km. Interestingly, Ganymede is locked in synchronous rotation and the center of the furrow system coincides with the anti-Jovian longitude (180°W). This indicates the existence of large mass anomaly created by the impact (N. Hirata et al. 2020, Icarus 352, 113941). The largest impact basin on Pluto, the Sputnik Planitia, is also located very close to the longitude of Pluto’s tidal axis. The basin possesses a positive gravity anomaly generated by nitrogen deposit and subsurface ocean, which explains the reorientation of Pluto along the tidal axis (F. Nimmo et al. 2016, Nature 540, 94-96). Similarly, we consider reorientation of Ganymede driven by furrow-forming impact. As a result, structures subsequent to the impact, such as ejecta deposit and icy shell thinning, can yield a sufficient positive gravity anomaly to cause the reorientation of Ganymede.