Thalassa is the second innermost moon of Neptune, and the seventh largest. It orbits Neptune every seven and a half hours. It is irregularly shaped and roughly 80km in diameter. It was discovered in September 1989 from images taken by the Voyager 2 probe. Thalassa is also the Greek word for sea.

This piece is in the form of a passacaglia with a short coda. It was first written for string quintet for a workshop at the CoMA Midwinter Composers’ course in January 2013. It has been arranged for open score ensemble.