Neptune's distant moon Nereid may be the sole survivor of the planet's original satellite system, according to new research published Wednesday in Science Advances. The findings suggest the moon managed to escape destruction when Neptune's largest moon Triton arrived billions of years ago and disrupted the existing lunar companions.

A team led by the California Institute of Technology used NASA's James Webb Space Telescope to study Nereid's composition and orbital characteristics. The observations revealed that Nereid contains more ice than typical objects from the Kuiper Belt, the frigid outer region of the solar system where many captured moons are believed to originate.

Nereid, discovered in 1949 by Dutch astronomer Gerard Kuiper, follows an extremely elliptical orbit around Neptune that takes nearly an Earth year to complete. The moon travels as close as 1 million miles to Neptune at one point and as far as 6 million miles at the other end of its egg-shaped path. This unusual orbital pattern has long puzzled scientists studying the 220-mile-wide satellite.

The research suggests that when Triton was captured by Neptune's gravity billions of years ago, it scattered the planet's original moons and sent them on destructive collision courses. Nereid likely survived by being pushed into its current extreme orbit, while other original moons were destroyed in the cosmic upheaval.

"We don't have all that much evidence left around Neptune — the system doesn't have very many moons left," said study author Matthew Belyakov of Caltech. The observations "strongly rule out" that Nereid wandered into Neptune's system from elsewhere and was captured by the planet's gravity.

Neptune currently has 16 known moons, far fewer than the other giant planets in the solar system. Saturn leads with 292 moons, while Jupiter and Uranus also have significantly more satellites than Neptune. Scientists believe Neptune's innermost moons likely formed from the debris of original satellites destroyed during Triton's arrival.