Trident, a new mission competing for selection under NASA’s Discovery Program, would explore Triton, a unique and highly active icy moon of Neptune. Voyager 2 showed that Triton has active resurfacing with the potential for erupting plumes and an atmosphere. Coupled with an ionosphere that can create organic snow and the potential for a subsurface ocean, Triton is an exciting exploration target to understand how habitable worlds may develop in our Solar System and beyond. Using a single flyby, Trident would map Triton, characterize active processes and determine whether the predicted subsurface ocean exists.
Voyager 2 image of Triton showing the south polar region with dark streaks produced by geysers visible on the icy surface. Image credit: NASA / JPL.
“Triton has always been one of the most exciting and intriguing bodies in the Solar System,” said Dr. Louise Prockter, director of the Lunar and Planetary Institute/Universities Space Research Association and principal investigator of the proposed Trident mission.
“I’ve always loved the Voyager 2 images and their tantalizing glimpses of this bizarre, crazy moon that no one understands.”
Figuring out what factors lead to a solar system body having the necessary ingredients to be habitable, which include water, is one of Trident’s three major goals.
The spacecraft would carry an instrument to probe the magnetic field of Triton to determine if an ocean lies inside, while other instruments would investigate the intense ionosphere, organic-rich atmosphere and bizarre surface features.
A second goal is to explore vast, unseen lands. Triton offers the largest unexplored solid surface in the Solar System this side of the Kuiper Belt.
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.
And Trident would use its full-frame imaging camera to capture the same plume-rich area Voyager 2 imaged — in full ‘Neptune-shine,’ when the Sun’s reflected light illuminates the dark side of Triton.
That way scientists could observe changes since the last visit and learn more about just how active Triton is.
Trident’s third major goal is to understand how that mysterious surface keeps renewing itself.
The surface is remarkably young, geologically speaking (possibly only 10 million years old) and has almost no visible craters.
There’s also the question of why it looks so different from other icy moons, and features unusual landforms like dimpled cantaloupe terrains and protruding walled plains.
The answers could shed light on how landscapes develop on other icy bodies.
Trident would explore 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. Image credit: NASA / JPL-Caltech.
“Triton is weird, but yet relevantly weird, because of the science we can do there,” said Trident project scientist Dr. Karl Mitchell, a researcher at NASA’s Jet Propulsion Laboratory.
“We know the surface has all these features we’ve never seen before, which motivates us to want to know ‘How does this world work?’”
“As we said to NASA in our mission proposal, Triton isn’t just a key to solar system science — it’s a whole keyring: a captured Kuiper Belt object that evolved, a potential ocean world with active plumes, an energetic ionosphere and a young, unique surface.”
The proposed launch date in October 2025 (with a backup in October 2026) would take advantage of a once-in-a-13-year window, when Earth is properly aligned with Jupiter.
The spacecraft would use the gravitational pull of Jupiter as a slingshot straight to Triton for an extended 13-day encounter in 2038.
“The mission designers and navigators are so good at this,” said Trident project systems engineer Dr. William Frazier, also from NASA’s Jet Propulsion Laboratory.
“After 13 years of flying through the Solar System, we can confidently skim the upper edge of Triton’s atmosphere — which is pretty mind-boggling.”
And it may seem that time moves slowly in the outer reaches of the Solar System, where Neptune’s years are long.
Ironically for Triton, the long timeline presents limitations. If Trident arrives before 2040, the team could perform its test of what’s powering the plume activity. Any later, and the Sun moves too far north… for the next hundred years.
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K.L. Mitchell et al. 2019. Implementation of Trident: A Discovery-Class Mission to Triton. 50th Lunar and Planetary Science Conference, abstract # 3200
This article is based on text provided by the National Aeronautics and Space Administration.
