A moon that wanders too close to its planet gets torn apart — not by crashing, but by TIDES. The planet pulls harder on the moon’s near side than its far side, and inside a critical distance (the Roche limit) that stretching beats the moon’s own gravity holding it together. The debris spreads into a RING. It’s why Saturn has rings and no big close moon. Slide the moon inward past the limit.
The Roche limit is the distance within which a body held together only by its own gravity is torn apart by TIDAL forces from a larger body. Tides arise from the DIFFERENCE in gravitational pull across the moon (stronger on the near side); when the satellite is closer than d ≈ 2.44·R·(ρᵧ/ρᵐ)⁵Ÿ (for a fluid body; R and ρ are the planet’s radius and density), that differential stretch exceeds the moon’s self-gravity and it disintegrates into a ring of debris — which is why planetary rings sit inside the Roche limit and large moons orbit outside it. A fail-loud self-check throws unless, inside the limit, the tidal force exceeds the moon’s self-gravity. ◆ real celestial mechanics, node-verified.
The fluid Roche limit (~2.44 R; a rigid body survives closer, ~1.26 R); real disruption depends on the moon’s strength and spin — the tides-beat-self-gravity-inside-the-limit mechanism is exact.