Astronomers using the NASA/ESA Hubble Space Telescope have revealed more about the origin of Neptune's smallest moon. The tiny moon, with an estimated diameter of only about 34 km, was named Hippocamp.The moon, which was discovered in 2013, is believed to be a fragment of its larger neighbour Proteus. It probably chipped off some 4 billion years ago and repeatedly smashed up and reassembled."The first thing we realised was that you wouldn't expect to find such a tiny moon right next to Neptune's biggest inner moon," said Mark Showalter. Hippocamp, formerly known as S/2004 N 1, is named after the sea creatures of the same name from Greek and Roman mythology.