Grand Finale
The final phase of the Cassini mission to saturn: 22 “proximal orbits” between April and September 2017 that took the spacecraft between the planet’s cloud tops and its innermost ring, followed by a controlled atmospheric plunge into Saturn on September 15, 2017.
Scientific results
- Saturn rotation rate — pinned at approximately 10.7 hours via close-in gravitational and magnetic field measurements; Voyager-era data could not resolve this.
- Gravitational and magnetic field structure — fine-scale measurements of Saturn’s interior dynamics.
- Ring composition and mass — direct sampling of ring-particle infall and high-resolution mass estimates.
- Magnetosphere — high-latitude ion and plasma data feeding into the 2026 Xu et al. result on Saturn’s afternoon-shifted magnetic cusp.
(src-cassini-huygens-ocean-worlds-2026-04)
Rationale for destruction
The atmospheric plunge was a planetary-protection decision: rather than leave Cassini in an unstable orbit that might eventually crash into enceladus or titan and contaminate a potentially habitable environment, NASA chose to destroy the working spacecraft. The decision is a canonical case in modern planetary protection policy.