A new mission competing for selection under NASA's Discovery Program would explore Neptune's largest moon, Triton, which is potentially an ocean world with liquid water under its icy crust. Trident aims to answer the questions outlined in the graphic illustration above.

The questions fall under Trident's three main goals. The first goal is to explore the factors that lead to a solar system body having the necessary ingredients — including water — to be habitable.

A second goal is to explore vast, unseen lands. Most of what we know of the moon came from Voyager 2 data. But we've only seen 40% of the moon's surface; Trident would map most of the remainder.

Trident's third major goal: to understand how Triton's surface keeps renewing itself. The surface is remarkably young, geologically speaking (possibly only 10 million years old in a 4.6-billion-year-old solar system) and has almost no visible craters.

The Trident team is one of four developing concept studies for new missions. Up to two will be selected by summer 2021 to become a full-fledged mission and will launch later in the decade.