When you look up into the sky at night, the Earth’s Moon is the brightest object you can see. But don’t let your eyes fool you; the solar system encompasses dozens of moons, most of which orbit the solar system’s outermost giant gassy and icy planets.
The vast majority of the solar system’s moons are somewhat uninteresting, but a small number of them stand out to planetary scientists because of how bizarre they are. Among the latter is Neptune’s largest natural satellite, Triton.
Image Credit: NASA/JPL/U.S. Geological Survey
For a moon, Triton seems to exhibit an extraordinary number of unusual characteristics. First and foremost, it follows a retrograde orbit, which means that it orbits Neptune in the opposite direction of most other moons in the solar system as they encircle their host planets. Moreover, Triton is geographically active, exhibiting an atmosphere, actively-spewing surface geysers, and tectonic activity, among other things.
Fueled by inspiration from Discovery-class missions like New Horizons, scientists from NASA’s Jet Propulsion Laboratory recently took the stage at the 50th Lunar and Planetary Science Conference 2019 in The Woodlands, Texas to propose their plans to launch a similar cost-effective mission dubbed Trident by 2026 that would probe Neptune’s moon Triton within the next couple of decades.
“New Horizons has effectively demonstrated the scientific value of fast flybys in the outer solar system,” the scientists elucidated in their paper.
“Trident's encounter with Triton will be similarly rapid, using remote sensing instruments with large apertures and high angular resolution sensors that operate millions to tens of thousands of kilometers before closest approach. Data is collected over several days around the encounter, and returned over the course of one year.”
The year 2026 was explicitly selected for the proposed Trident mission because of a rare alignment of the planets that would allow the spacecraft to slingshot around Jupiter in a maneuver that NASA calls a ‘gravity assist.’ Upon arriving, the mission would overlap with one of Triton’s 40-year seasonal changes, giving scientists a unique opportunity to study the moon’s atmosphere as the seasons shift.
As you might come to expect, Trident would also provide a modern look at Triton’s gas-spewing surface geysers and help to unravel the mysteries regarding where the moon came from and why it sports a retrograde orbit around Neptune.
NASA’s tried and true New Horizons probe has shown us time and time again that fly-by missions can be incredibly useful in studying distant worlds, and we expect that Trident would be no different. Then again, only time will tell if the mission will actually launch and go on to study one of the solar system’s strangest moons.