50 Dollars First Probe Beyond the Solar System

The Marshall Islands began issuing commemorative coinage in 1986 following the Compact of Free Association with the United States, which granted the republic self-governance while the U.S. retained defense authority. This piece marks Voyager 2's August 1989 Neptune flyby — the closest approach of any spacecraft to that planet, at roughly 4,950 kilometers above the cloud tops — which effectively completed the outer planet grand tour that mission planners had conceived back in the early 1970s when a rare planetary alignment made the trajectory possible.