Trident, a NASA low cost mission to Triton Options

[MarcF]

Jet Propulsion Laboratory scientists proposed a new low cost mission to Triton, to check for the presence of an internal ocean inside the moon.

https://www.nytimes.com/2019/03/19/science/...sa-trident.html

"Unlike multibillion dollar proposals for spacecraft that the agency has usually sent to the outer solar system, this spacecraft, named Trident, aims to be far less expensive, the mission’s scientists and engineers said, or the price of a small mission to the moon."

To get to Triton, the spacecraft would fly in a fast, straight trajectory after an orbital assist from Jupiter, similar to the flyby that was used by the New Horizons spacecraft to visit Pluto in 2015. It would rely on a payload of scientific instruments to conduct ocean detection and atmospheric and ionospheric science. The spacecraft would photograph the entirety of Triton, which is the largest object in the solar system that has not yet been fully imaged.
Timing is also critical because of the moon’s changing seasons as Neptune makes its orbit around the sun.

“In order to view the plumes that Voyager saw in 1989, we have to encounter Triton before 2040,” said Dr. Mitchell. Otherwise, because of the positions of the objects in their orbits, Triton will not be illuminated again for over eighty years.

Link to original abstract:
http://adsabs.harvard.edu/abs/2018DPS....5011415P

Fingers crossed !
Regards,
Marc.

[scalbers]

Interesting - have we past the Triton equinox yet?

[vjkane]

Here are links to two LPSC 2019 abstracts:

Trident science

Trident implementation

[titanicrivers]

Here is some news of interest to outer solar system exploration! https://www.nasa.gov/press-release/nasa-sel...he-solar-system
NASA has selected four Discovery Program investigations to develop concept studies for new missions. Although they’re not official missions yet and some ultimately may not be chosen to move forward, the selections focus on compelling targets and science that are not covered by NASA’s active missions or recent selections. Final selections will be made next year.

NASA’s Discovery Program invites scientists and engineers to assemble a team to design exciting planetary science missions that deepen what we know about the solar system and our place in it. These missions will provide frequent flight opportunities for focused planetary science investigations. The goal of the program is to address pressing questions in planetary science and increase our understanding of our solar system.

“These selected missions have the potential to transform our understanding of some of the solar system’s most active and complex worlds,” said Thomas Zurbuchen, associate administrator of NASA's Science Mission Directorate. “Exploring any one of these celestial bodies will help unlock the secrets of how it, and others like it, came to be in the cosmos.”

Each of the four nine-month studies will receive $3 million to develop and mature concepts and will conclude with a Concept Study Report. After evaluating the concept studies, NASA will continue development of up to two missions towards flight. One of the missions was TRIDENT!

Trident would explore Triton, a unique and highly active icy moon of Neptune, to understand pathways to habitable worlds at tremendous distances from the Sun. NASA’s Voyager 2 mission showed that Triton has active resurfacing generating the second youngest surface in the solar system with the potential for erupting plumes and an atmosphere. Coupled with an ionosphere that can create organic snow and the potential for an interior ocean, Triton is an exciting exploration target to understand how habitable worlds may develop in our solar system and others. Using a single fly-by, Trident would map Triton, characterize active processes, and determine whether the predicted subsurface ocean exists. Louise Prockter of the Lunar and Planetary Institute/Universities Space Research Association in Houston is the principal investigator. NASA’s Jet Propulsion Laboratory (JPL) in Pasadena, California, would provide project management.

[scalbers]

Apparently the equinox (for most complete viewing) is right about 2040.

[JRehling]

Triton has a weird (and, of course, very long) "season" but, yes, the sub solar latitude will be nearly equatorial around 2040. It also was just a bit south of equatorial in 1989, so the season will be similar to the Voyager 2 flyby. For the entire time between those, the sub solar latitude has been considerably south and the north polar region has not seen daylight in decades.

As a convenient comparison, the length of a Tritonian day is about the same as on Pluto so one might expect similar coverage of a near-encounter and far-encounter hemisphere to that which New Horizons yielded at Pluto. We could have better luck with neptune-shine images of Triton's sub-Neptunian hemisphere since Neptune is brighter than Charon.

[titanicrivers]

An article in Forbes on Trident. Not sure there's a lot of new info but it's encouraging there's interest in this mission. The article can be found here: https://www.forbes.com/sites/brucedorminey/...r/#8bcabdd32945

[Julius]

While it's nice to hear about an interest in doing a Triton mission, it's a pity it would have to be a flyby mission. Personally I would prefer an orbiter mission but again timing and costs determine the planning of such missions.

[Phil Stooke]

More on Trident here:

https://www.lpi.usra.edu/sbag/meetings/jun2..._vpublished.pdf

(from the recent Small Bodies Assessment Group meeting)

talking about some small body observations possible around the main mission.

Phil

[Julius]

Triton has a weird (and, of course, very long) "season" but, yes, the sub solar latitude will be nearly equatorial around 2040. It also was just a bit south of equatorial in 1989, so the season will be similar to the Voyager 2 flyby. For the entire time between those, the sub solar latitude has been considerably south and the north polar region has not seen daylight in decades.

As a convenient comparison, the length of a Tritonian day is about the same as on Pluto so one might expect similar coverage of a near-encounter and far-encounter hemisphere to that which New Horizons yielded at Pluto. We could have better luck with neptune-shine images of Triton's sub-Neptunian hemisphere since Neptune is brighter than Charon.

So by 2040 as Trident flies through the Neptune system, it will be end of summer in the southern hemisphere, do we expect most of the south polar ice deposit seen at the time of Voyager disappear and instead an icy polar cap developing over the northern hemisphere??

[JRehling]

"Ice" means something pretty broad at Triton. Certainly water ice is as solid as a rock in any situation where climate is the only consideration. Geological activity may melt water ice, but heat from the Sun never will.

Nitrogen, methane, or carbon monoxide ice may be a different story. I don't think anyone can do better than speculate because the chemistry could be pretty complex and we've never witnessed a change of seasons on Triton in detail. As noted in a previous discussion of Titan, the distinctions we draw on Earth between geological activity and climate may not be so sharp on other worlds.

Triton only gets 1/900th the solar heat that the Earth does, so we might expect the Sun's role to be relatively diminished there. On the other hand, "days" can last decades near the poles. We see at Callisto and Iapetus how long days on a cloudless body can cause accumulated effects over time.

I think the upshot is: Nobody knows and that would be one of the things that future missions may work out. Also, future telescopes will be able to monitor Triton at regional-scale resolution on a permanent basis. I'd expect some interesting observations in the 2040s. Let me set my clock alarm for then.

[antipode]

Are any of the big TNOs we know of in the right place for a post Neptune flyby?
I'm assuming as Triton science would take precedence, the encounter geometry would be fixed.
How much fuel would Trident carry to allow for post encounter maneuvering?
Going all that way for a flyby would be disappointing unless there's a good secondary target.

P

[Explorer1]

At Phil's link one of the slides summarizes: basically they are at an early stage of looking for targets, but they apparently can somewhat modify the geometry of the flyby to put them on a path towards a TNO (within reason).

[vjkane]

Are any of the big TNOs we know of in the right place for a post Neptune flyby?
I'm assuming as Triton science would take precedence, the encounter geometry would be fixed.
How much fuel would Trident carry to allow for post encounter maneuvering?
Going all that way for a flyby would be disappointing unless there's a good secondary target.

P

If the mission is selected, I would expect a dedicated search for both Centaurs and TNOs reasonably close to the flight line. Because the Triton encounter largely fixes the exit trajectory leaving the Neptune system, the spacecraft can't use a gravity assist to target a specific known body beyond Neptune. So, targets of opportunity.

[Phil Stooke]

There is just a little bit of flexibility by adjusting (within limits) where in its orbit Triton is at flyby. It can't be very different from the nominal flyby position because of the mapping goals, but it can vary a little bit, opening up a certain spread of post-Neptune trajectories.

From the link above:

Trident proof-of-concept: 2006 QL181.
• Cubewano (cold) type (~150 km), like Arrokoth (30-45 km diameter).
• 64,000,000 km encounter in Feb 2041, near 40 AU (14.5-yr after launch).
• Delay to Triton encounter (~70 m/s delta-v) enables targeted 10000 km flyby.

Phil

[antipode]

Interesting, thanks Phil. Would be nice to have a dynamically 'hot' target, but beggars cant be choosers.

P

[Webscientist]

Here is a simulated view of Neptune from the surface of Triton. I produced it in 2020 for an article upon the Trident project in the journal of my astronomy club:

We will compare to reality in a few decades !

(The apparent size of Neptune is well respected in the simulated view from my "smartphone": it would represent a disk whose apparent diameter is about 8 arc degrees or 15 times the apparent diameter of the Moon as seen from the Earth).

Attached thumbnail(s)

 

[JRehling]

That's a powerful image! Triton would be getting a lot of missions if it weren't for the travel time, and an image like that can do a lot to bring Triton forward in people's minds.

I'm not sure what color the skies are on Triton, but Neptune would contribute powerfully.

[Webscientist]

Thanks,
A way for me to explore in advance that mystical world that may turn out to be more exotic than expected in fact.
I often try to imagine the type of horizon we would get from the surface of Pluto or Triton since the atmosphere of Triton is so thin ( slightly denser than Pluto's atmosphere at "sea level").
I imagined a dull sky and a darker sky toward the zenith. Intuitive logic I would say!
For the appearance of the soil, it is quite speculative I would say because we only have one image of the surface of a planetary body of the outer solar system.

[titanicrivers]

Fascinating image Webscientist! The foreground is what I imagined the 'cantaloupe' Triton surface might appear close up. Agree with JRehling such images and others https://www.google.com/search?q=neptune+fro...50&biw=1536 would inspire more interest in outer solar system exploration.

[Webscientist]

The foreground is what I imagined the 'cantaloupe' Triton surface might appear close up.

Thanks again,
For the cantaloupe, I used some "ingredients" not related to the cantaloupe terrain Voyager 2 had observed, without the purpose of producing those cantaloupe structures but the outcome reveals small scale-cantaloupes. Satisfied!
It also reminds me of the distorted surface the Phoenix lander had observed on Mars.
Let's hope we'll get higher resolution images of those cantaloupe terrains in the near future!

[Station]

Here goes my rendition about lander (in this case I "borrowed" Viking ) on the surface of Triton. Few liquid nitrogen geysers on the far horizon... thin, barely visible atmosphere.

[Marcin600]

...Few liquid nitrogen geysers on the far horizon...

Are the visible geyser plumes on Triton really composed of liquid nitrogen or are they nitrogen crystals (with some darker impurities)?

[scalbers]

Station's rendition seems consistent with small optical thickness of Triton's atmosphere, though it might be slightly more visible. Looking near the horizon it should look brighter especially in the direction of the sun.

https://agupubs.onlinelibrary.wiley.com/doi....1029/92JE00945

The size of the haze particles suggests a bluish color of preferential scattering due to the Angstrom exponent effect. Any methane gas absorption, or absorption by the haze particles could modify this color.

[Webscientist]

Thanks Station for your nice art work. The crescent of the giant planet (whose appearance constantly evolves) from the surface of Triton must be breathtaking.
The Sun located at 30 Astronomical Units must appear as a really bright star even if its apparent diameter is only 1/30 the apparent diameter of the Moon from the Earth. I remember the simulator "Pluto Day" to represent the luminosity on the surface of Pluto. Undoubtedly, on Triton, it is not the complete darkness at mid-day!
The apparent diameter of Neptune would be around 480 times the apparent diameter of the Sun!

[Station]

Fantasy continues

This time I created something based on the uranian system. I titled it "Lost on Miranda"

[titanicrivers]

Possibly, that explorer is close to Verona Rupes (the tallest cliff in the solar system!). https://en.wikipedia.org/wiki/Verona_Rupes

[Phil Stooke]

Often misrepresented! That cliff is a talus deposit at the angle of repose. If you jumped off it you would slide down it, not fall through space until you hit the bottom. My evidence? - the full image or a mosaic of images from this sequence shows where the horizon would be just beyond the terminator. It's not perpendicular to the cliff. Bring skis, not airbags.

Phil

[titanicrivers]

Thanks Phil. Should have searched UMSF first to find your abstract https://www.lpi.usra.edu/meetings/lpsc1991/pdf/1667.pdf from LPSC XXII. Maybe should be an addendum to the Wikipedia article.

[JohnVV]

the renderings got me thinking , so...

a crop from Voyager image of Triton


using Shape from Shade a height map is created
-- i used a 32 bit tiff image


and a quick work in progress rendering of near the surface in blender


the hills are a bit pronounced

[antipode]

Hi Phil

Sorry if this is getting a bit OT, but regarding Verona Rupes, would not the angle of repose be rather steep in the weak Mirandian gravity?
Im assuming that water ice at these temperatures would have the mechanical strength of a silicate rock?
Or am I missing something about the calculation of an angle of repose?

P