Editor's note: This article was updated March 25 at 11:40 a.m. ET to account for the recent discovery of new moons around Saturn and Jupiter. The total number of planetary moons and small-body ...

Neptune has a complicated life story, and its moon Nereid might be the only one left standing from the planet’s multibillion-year history.

Nereid, Neptune’s third-largest moon, could be the only intact survivor from an ancient set of moons destroyed early in the solar system’s history, according to a new analysis based on data from the ...