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Neptune’s newest, tiniest moon likely piece of bigger one
CAPE CANAVERAL - Neptune's newest and tiniest moon is probably an ancient piece of a much larger moon orbiting unusually close. In the journal Nature on Wednesday, California astronomers shine a light on the 21-mile-diameter moon Hippocamp, named after the mythological sea horse.
The SETI Institute's Mark Showalter discovered Neptune's 14th moon in 2013, using Hubble Space Telescope images. Showalter and his research team theorize Hippocamp was formed from debris created billions of years ago when a comet slammed into Proteus, the largest of Neptune's inner moons. The two moons orbit just 7,500 miles apart and were likely even closer in the past before Proteus migrated outward.
Scientists have long believed Neptune's inner moons were repeatedly broken apart by collisions with comets, according to Showalter.
"The discovery of Hippocamp, orbiting so close to the much larger moon Proteus, provides a particularly dramatic illustration of the Neptune system's battered history," Showalter said in an email.
While the researchers said they cannot rule out the possibility that Hippocamp is unrelated to Proteus, the moon's "tiny size and peculiar location" support their formation theory.