Trident, a Proposal to Explore Neptune’s Largest Moon

Credits: NASA

NASA’s Discovery Program has proposed four missions to develop our understanding of the Solar System, including Trident, a return to Neptune.

With a recently announced set of discovery missions, NASA is eyeing a possible mission to Triton, the largest moon of Neptune. The actual winner will be decided at a later date, leaving plenty of time to consider the contenders: an Io volcano observer, and two in-depth missions to study the history and makeup of Venus.

Ocean Worlds, Earth, and a Boost from Jupiter

The Trident mission, if launched, would take flight on an Atlas V rocket in 2026. The closest flyby would occur mid-2038. Millions of kilometers before that, the Trident craft would have already been observing the moon with its high-power instruments.

Proposed instruments include spectrometers, two cameras, a magnetometer, and radio equipment. With these, Trident will be able to determine whether a liquid ocean exists on Triton. This follows an escalating interest in the study of ocean worlds and icy bodies. Scientists believe these desolate worlds have the highest chance of harboring life, an idea that draws illusions of the upcoming Europa Clipper mission.

A large part of NASA’s interest in Triton comes from an observational window that will allow the launch to use Jupiter as a boost, this move is called a gravity assist, saving both time and fuel in reaching the immense distance to Neptune (a 30-AU journey). Additionally, there will be an opportunity for Trident to study Jupiter and Io whilst boosting. The actual flyby of Triton will include the assortment of instruments mentioned, plus high-resolution imagery that will aid scientists in mapping the icy moon.

Why Is Triton a Special Candidate?

Global color mosaic of Triton, taken in 1989 by Voyager 2 during its flyby of the Neptune system.
Triton in 1989, Voyager 2 (Credit: NASA/JPL/USGS)

Understanding why a single flyby is valuable requires an understanding of the past. When New Horizons launched in 2006, it proved the value of single flybys through the data it sent back. On January 1, 2019, New Horizons flew past the farthest explored body Ultima Thule. The mission demonstrated what Triton will reenact with an approach to Neptune.

Like New Horizons, the Triton mission will set out to answer some questions regarding the Kuiper Belt. Scientists currently believe Triton is a captured body launched from the Kuiper Belt millions of years ago. As a moon, it is especially unusual due to its retrograde orbit—Triton has an orbit in the opposite direction of Neptune.

A key event in the mission timeline occurs at the climax, when Trident is flying closest to Triton: the probe will enter the atmosphere by a small margin, taking a scientific dip into the nitrogen atmosphere and providing time for the magnetometer to detect the possible interior ocean. You can access the proposed timeline straight from NASA, here.

Lasting Impact of Trident

What happens in 2038, when Trident has come and gone, saying goodbye to Neptune and Triton altogether? For the next year, scientists will receive a steady stream of data to sift through. In the long term, NASA hopes the mission will benefit the current themes of human habitability on foreign worlds, especially ones like Europa and Triton.

From ice volcanos to a young, perpetually regenerating surface, Triton holds more answers than we could possibly know.

The goal of NASA’s Discovery Program has never deviated from the thirst for more knowledge about our Solar System. If chosen, the Trident mission will bring the program to valuable new heights—and if there is an ocean to be found, depths.

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Brown, K. (2020, February 13). NASA Selects 4 Possible Missions to Study Secrets of the Solar System. Retrieved February 17, 2020, from

K.L. Mitchell, M. Prockter, W.E. Frazier, W.D. Smythe, B.M. Sutin, D.A. Bearden, The Trident Team, Jet Propulsion Laboratory (2020, February 13). Implementation of Trident: A Discovery-Class Mission to Triton

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