Neptune's Moon Nereid Might Be the Sole Intact Survivor of an Ancient Lunar Collision

NASA / JPL Neptune, the farthest planet from the sun, is surrounded by 16 known moons—and many of them are weirdos.

Now, researchers propose that one of those oddballs, a wide-orbiting moon called Nereid, is the sole intact survivor of an ancient lunar collision. The findings, described May 20 in the journal Science Advances, could provide insight into the giant planet’s history, and thus, that of the early solar system.

The solar system’s eighth planet has a strange collection of moons compared to its fellow outer planets, Jupiter, Saturn and Uranus. Those three have more typical lunar companions, with several large satellites that orbit in line with their planet’s equators and smaller, farther moons with tilted orbits.