Considered one of 4 ideas being thought-about for a Discovery Program mission, Trident would examine one of many photo voltaic system’s most uncommon worlds.
When NASA’s Voyager 2 spacecraft flew by Neptune’s unusual moon Triton three a long time in the past, it wrote a planetary science cliffhanger.
Voyager 2 is the one spacecraft ever to have flown previous Neptune, and it left lots of unanswered questions. The views have been as gorgeous as they have been puzzling, revealing large, darkish plumes of icy materials spraying out from Triton’s floor. However how? Pictures confirmed that the icy panorama was younger and had been resurfaced again and again with contemporary materials. However what materials, and from the place?
How may an historical moon six occasions farther from the Solar than Jupiter nonetheless be energetic? Is there one thing in its inside that’s nonetheless heat sufficient to drive this exercise?
A brand new mission competing for choice below NASA’s Discovery Program goals to untangle these mysteries. Known as Trident, just like the three-pronged spear carried by the traditional Roman sea god Neptune, the group is one in all 4 that’s creating idea research for brand new missions. As much as two can be chosen by summer season 2021 to turn out to be a full-fledged mission and can launch later within the decade.
Investigating how Triton has modified over time would give scientists a greater understanding of how photo voltaic system our bodies evolve and work.
The eccentricities of Triton may fill an almanac: As Neptune rotates, Triton orbits in the other way. No different massive moon within the photo voltaic system does that. And Triton’s orbit lies at an excessive tilt, offset from Neptune’s equator by 23 levels. About three-quarters the diameter of our personal Moon, Triton isn’t the place it was once, both. It possible migrated from the Kuiper Belt, a area past Neptune of icy our bodies left over from the early photo voltaic system.
Triton has an uncommon environment, too: Stuffed with charged particles, a layer known as the ionosphere is 10 occasions extra energetic than that of some other moon within the photo voltaic system.
That final trait is particularly unusual, as a result of ionospheres usually are charged by photo voltaic power. However Triton and Neptune are removed from the Solar – 30 occasions farther from the Solar than Earth, so another power supply should be at work. (It takes 165 Earth years for Neptune to finish one orbit across the Solar.)
And Triton’s local weather is dynamic and altering, with a gradual circulation of natural materials, possible nitrogen, snowing onto the floor.
“Triton has always been one of the most exciting and intriguing bodies in the solar system,” mentioned Louise Prockter, director of the Lunar and Planetary Institute/Universities House Analysis Affiliation in Houston. As principal investigator, she would lead the proposed Trident mission, and NASA’s Jet Propulsion Laboratory in Southern California would handle it. “I’ve always loved the Voyager 2 images and their tantalizing glimpses of this bizarre, crazy moon that no one understands,” Prockter added.
A Three-Pronged Method
These mysterious plumes Voyager 2 noticed are particularly intriguing. Plumes seen on Saturn’s moon Enceladus, and probably current on Jupiter’s moon Europa, are considered brought on by water from the inside being pressured by means of thick, icy crusts. If an ocean is the supply of the plumes on Triton (which lies a lot farther out within the photo voltaic system than Europa and Enceladus), the invention would give scientists new details about how inside oceans kind. Not like different identified ocean worlds, Triton’s potential ocean possible developed after it was captured by Neptune’s gravity.
It could additionally develop scientists’ understanding of the place we’d discover water. Determining what components result in a photo voltaic system physique having the required substances to be liveable, which embrace water, is one Trident’s three main objectives. The spacecraft would carry an instrument to probe the moon’s magnetic area to find out if an ocean lies inside, whereas different devices would examine the extraordinary ionosphere, organic-rich environment and weird floor options.
A second purpose is to discover huge, unseen lands. Triton presents the most important unexplored stable floor within the photo voltaic system this facet of the Kuiper Belt. Most of what we all know of the moon got here from Voyager 2 information, however we’ve solely seen 40% of the moon’s floor. Trident would map a lot of the the rest.
And Trident would use its full-frame imaging digital camera to seize the identical plume-rich space Voyager 2 imaged – in full “Neptune-shine,” when the Solar’s mirrored gentle illuminates the darkish facet of Triton. That means scientists may observe adjustments for the reason that final go to and study extra about simply how energetic Triton is.
Trident’s third main purpose is to know how that mysterious floor retains renewing itself. The floor is remarkably younger, geologically talking (probably solely 10 million years previous in a 4.6-billion-year-old photo voltaic system) and has virtually no seen craters. There’s additionally the query of why it appears so completely different from different icy moons, and options uncommon landforms like dimpled “cantaloupe terrains” and protruding “walled plains.” The solutions may make clear how landscapes develop on different icy our bodies.
“Triton is weird, but yet relevantly weird, because of the science we can do there,” mentioned Karl Mitchell Trident challenge scientist at JPL. “We all know the floor has all these options we’ve by no means seen earlier than, which motivates us to need 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.”
This interactive mannequin of Triton isn’t full however relies on obtainable pictures. To see the way it compares to our personal Moon, zoom in and provides the moons a spin, or use the search operate at backside for extra. Credit score: NASA/JPL-Caltech
The proposed launch date in October 2025 (with a backup in October 2026) would benefit from a once-in-a-13-year window, when Earth is correctly aligned with Jupiter. The spacecraft would use the gravitational pull of Jupiter as a slingshot straight to Triton for an prolonged 13-day encounter in 2038.
“The mission designers and navigators are so good at this,” mentioned JPL’s William Frazier, challenge programs engineer of Trident. “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 might appear that point strikes slowly within the outer reaches of the photo voltaic system, the place Neptune’s years are lengthy. Paradoxically for Triton, the lengthy timeline presents limitations. If Trident arrives earlier than 2040, the group may carry out its take a look at of what’s powering the plume exercise. Any later, and the Solar strikes too far north … for the following hundred years.
Learn extra data on Discovery Mission proposals chosen to develop idea research here.