Future Pluto Missions – We Have to Go Back!

Why is that? Why do we need another Pluto mission? Didn’t a flyby perform sufficient amount of Pluto exploration? Why do we still talk about Future Pluto Missions? And what do scientists expect to find by visiting Pluto again?

You will get the answers.

As the answers to above questions give the green light, we will detail possible and up-to-date missions and key points about them.

Is It Worth To Visit Pluto Again?

The answer of this question depends on so many parameters.

As New Horizons Spacecraft carried Earth‘s flag to Pluto, performed some marvelous imaging and headed on towards other targets in depths of Kuiper Belt; fantastic Pluto days were partially over. Because there is no turning back for the spacecraft.

Pluto and its surface names
Source: JHUAPL, Credits: NASA/JHUAPL/SwRI/Marco Di Lorenzo/Ken Kremer

Close-by images of Pluto promised amazing new information for planetary scientists. It was seen that many features including the surface formation, colors, atmosphere were not alot like any other planet. Pluto was found to be an active, living planet; not a dead one as anticipated!

We expect that the bigger rocky objects beyond Neptune are typically similar to each other. However, New Horizons was the first chance to observe such an object in details. And although it uncovered some of the facts about Pluto and Kuiper Belt, increasing amount of information increased the amount of unknowns!

After a quick glance, we still require more data to fully understand how Pluto and other big icy rocks in Kuiper Belt are formed and evolved. This means, being the closest suitable candidate of those big icy rocks and being the source of preliminary knowledge; Pluto still draws the greatest interest in terms of a potential mission to Kuiper Belt Objects.

Why Is New Horizons Mission Not Sufficient? Why Is Another Pluto Visit Needed?

Those are quite fair questions. But first thing to ask is, what were the goals of New Horizons Mission?

New Horizons Spacecraft Trajectory
Trajectory of New Horizons Spacecraft. Credits: NASA/JHUAPL/SwRI/Alex Parker

New Horizons was a pioneer to observe basics of a planetary body beyond Neptune in details. On the other hand, although the project assured its succeess for every scientific goal that’s planned; it was a costly (more than $700 million) but a limited mission .

New Horizons is a Kuiper Belt and Pluto flyby mission. And the Pluto phase of mission majorly covered detailed mapping and analysis of surface features and composition of Pluto and Charon, and detailed analysis of Pluto atmosphere.

That sounds like more or less everything.. Than what’s left to know more about Pluto System?

Surface Mapping

As a part of its major goals, New Horizons successfully mapped Pluto surface and Charon surface. (See articles Pluto Map and Charon Map for more details). However it was only a flyby and our planetary buddies do rotate quite slowly. Since 1 Pluto and Charon day is 6.4 Earth days, for capturing all details on both spheres with high resolution, a spacecraft has to orbit bodies by scanning and covering pretty much all parts of them. Since that was not the case for New Horizons, spacecraft cameras could only observe less than a half of both Pluto and its biggest moon Charon with higher resolution.

Global and zoomed view of Charon
A zoomed image of Charon. Credit: NASA/JHUAPL/SWrI

New Horizons cameras did capture the far side of Pluto and Charon days before the encounter. However the qualities of those images are not sufficient enough for detailed mapping.

But when it comes to smaller Pluto Moons; they were not a part of the plan in the first place! Just months before the launching, Hydra and Nix were discovered. And after the spacecraft skipped past Uranus orbit, two more moons were discovered which were later named Kerberos and Styx.

Actually even if they were discovered before the mission, it could never change anything because of the limited time for the flyby. Well, in any case the spacecraft imaged those 4 moons with best resolutions possible, which are lower than needed for a detailed study.

Variation of Pluto Surface and Atmosphere

As mentioned above, Pluto is an active planet. Two of those activities that scientists try to clarify are the variation of surface and atmosphere in time. Especially Pluto’s loose atmosphere attracts scientists’ extreme attention.

Due to Pluto’s highly elliptical orbit around Sun, seasons in Pluto can lead to dramatic changes. Those variations can be so dramatic that, as she moves away from Sun, Pluto atmosphere might be completely freezing, snowing onto the surface. And this truely increases the amount of planetary complexity.

Comparison of Pluto and Earth Atmospheres
In terms of volume, Pluto’s atmosphere is more than 350 times bigger than itself. Source here, Credit: JHUAPL

Apart from above sublimation-condensation cycle, Pluto surface is continuously shaped through tectonism, glaciation and winds. That’s why, observing those changes in both daily and seasonal basis with another visit will surely provide a total understanding of Pluto System’s behaviour.

We Can Learn More From Pluto System with Proper Instruments

Above is not the end. Thanks to New Horizons and following researches, scientists have strong evidences that Pluto has a subsurface ocean beneath its water ice crust. In addition to this, researches suggest signs of cryovolcanic activities in one or more mountainous regions.

Actually, such Earth-like formations were already presumed after New Horizons mission was settled and before it visited Pluto. However, only a flyby is not a good choice for verification of above, but as pointed out above; scientists were not sure about that before a flyby mission.

In addition to those fantastic features, we can still extract more data out of Pluto: We can measure surface and crust thickness, core activities in details and even sample its atmosphere with a great precision.

Inside of Pluto
If you take a slice of Pluto out, this is more or less what it is; except the predicted ocean. Source: Wikimedia, Credit: NASA/JHUAPL/SWrI

Future Pluto Missions – A Pluto Orbiter / Lander

Ok, let’s spill the beans now.
After New Horizons Spacecraft took a quick glance to Pluto System, a new Pluto mission was noised around without pausing.

As mentioned earlier, only chance to succeed with above is an orbiter or a combined landing mission to Pluto or Pluto System.

In order to make it happen, there are some key aspects to take into account.

First of all, an orbiter or landing spacecraft should include suitable tools. Comparing to New Horizons Spacecraft scientific payload, there should be several additions to the scope.

  • A special radar device for measuring the thickness of glaciers,
  • A mass spectrometer will be needed for sampling and detecting the materials in the atmosphere.
  • A specialized thermal mapper for resolving the glacial and cryovolcanic activities.
  • A specialized magnetometer for understanding the core activity.
  • Additional sampling and drilling tools and machines for surface material analysis in case of a landing mission.
Tenzing Montes - Pluto
There are some available and wide plains on Pluto surface. This image shows the Tenzing Montes and the dotted plain in the neighbourhood. Credit: NASA/SWrI/JHUAPL

When it comes to detection of the internal ocean and interior form of Pluto, the spacecraft should perform several tours around her and specially collected radio waves are needed to be analyzed.

Pluto Visit Plans After New Horizons

Shortly after New Horizons hailed Pluto, scientists started telling their ideas outloud. Especially Mr. Alan Stern, PI of New Horizons Mission who devoted most of his life to Pluto researches has been talking about this beginning with year 2016.

Alan Stern’s initial idea was placement of a lander to Charon and having a fixed Pluto observatory. This is a great idea considering the short distance between Pluto and Charon: Only 19.640 kilometers in average.

However he probably changed his mind because this can only enable observation of one side of Pluto because Pluto and Charon are tidally locked to each other.

Mr. Stern has been frequently expressing his thoughts for the next Pluto mission. Also In 2018, a team of scientists published a white paper including aspects for a future (orbiter) Pluto mission and their recommendations to NASA.

Gold Standard Pluto Kuiper Belt Mission – Future Pluto Missions

In addition to above, an exciting announcement arrived in the end of October 2019.

He announced that they are already planning a Pluto orbiter and Kuiper Belt mission for some time and gave several hints about it.

An illustration of Future Pluto Missions
An illustration of such project by Ron Miller. Source here, Credit: Ron Miller & Astronomy.com

He stated that the planned orbiter spacecraft is to be launched on December 2028 and to be orbitted to Pluto in 2046, for performing minimum two years of Pluto System studies and going on for next objects in Kuiper Belt until 2059. The project includes Pluto science with all above listed items and aims to reveal all secrets of Pluto.

Alan Stern states that they will be serving the project to NASA‘s next Planetary Decadal Survey taking place in 2020, which will announce its decisions latest in 2023.

Pluto Hop, Skip, and Jump – Future Pluto Missions

Another exciting mission report was prepared by Global Aerospace Corporation in 2017-2018 for NIAC (NASA Innovative Advanced Concepts). The project includes a plan to place a small lander on Pluto surface. The lander will then take advantage of Pluto’s low gravity and jump to several different locations on Pluto for various studies.

The project aims to launch its light spacecraft in 2029, arrive Plutolands in 2040 and perform its science for about 10-15 years.

One disadvantage of such mission is that, the mission will not continue to Kuiper-Lands but will end on Pluto.

Pluto Hop Skip and Jump - Future Pluto Missions
That’s how the spacecraft wanders around. Source here, Credit: Benjamin Goldman

Fusion-Enabled Pluto Orbiter and Lander – Future Pluto Missions

Another Pluto project noticed is called the Fusion-Enabled Pluto Orbiter and Lander. This project is created by Princeton Satellite Systems and is also served to NIAC in 2016-2017.

This mission has couple of interesting features compared to above. First thing is, the project uses direct fusion drive for thrusting, which makes the spacecraft quite fast. So fast that it can reach Pluto within 4-6 years! Although that sounds pretty fast, planned launching date after the long project development period is 2036.

In addition to this, the spacecraft will include both an orbiter and a lander which makes things more exciting! So while the lander handles its business down there, the orbiter will enjoy orbiting and imaging Pluto from its wide skies.

Future Pluto Missions – Technical Issues

Excluding the “long terms” of a future Pluto mission, above sounds easy right? Well, it’s easy to write but not to realize.

New Horizons Mission was an idea back from 1989‘s, however the mission is approved in 2001. Spacecraft is launched in 2006, reached to primary target Pluto in 2015 and is still on its way through depts of Kuiper Belt.

New Horizons Spacecraft Trajectory
New Horizons’ journey over time. Source here, Credit: NASA

This points out one thing: It takes time to prepare long term plans for such space missions to outer depths solar system, even the travelling takes much more longer time anything! In the meanwhile, huge leaps on technology makes your spacecraft flying with older technology! For better understanding, consider how smart phones started to evolve in between 2001 and 2015!

Luckily, this time we have a stepping stone here and scientists have better ideas and plans for next moves.

For both orbiter and landing missions, we need to build properly equipped and probably heavier spacecrafts which can accelerate fast enough, start to slow down in the halfway and settle to Pluto orbit. And for landing, we’ll need more power to maintain a balanced landing.

Beyond the huge costs of such a mission, those requirements make two things crucial: Travelling and Fuel strategies.

Travelling Strategy

While planning an efficient fuel strategy, one must also take travelling into account. This was an easier task for New Horizons Spacecraft since it was light enough. But although it was the fastest of its time, it took 9.5 years to approach to Pluto. So we are talking about a new mission having both heavier and faster spacecraft.

It might need to land as well! This is SpaceX’s Crew Dragon. Credit: SpaceX

Such challenges forced researchers to find more creative ways and challenge never means setback in today’s science!

Gravitational power of big objects in Solar System is always used for gravity assists when there’s a long distance to go for a spacecraft. In Pluto case, New Horizons Spacecraft used a respectable amount of gravity boost from Jupiter and proceeded on its trajectory without braking.

One challenge especially for an orbiter plan is both braking and then stabilization of the spacecraft in desired route. But luckily, this case is already solved! Scientists have ready-to-go calculations and models for a 2-years-long orbiter with almost zero fuel consumption!

In fact, the plan does not end here. To turn the mission into a more profittable and well-qualified one with incredible amount of cost saving and long term study advantage, there is one more trick. In the end of this pre-planned sequence, it’s proposed for the spacecraft to get out of Charon‘s gravitational influence without any fuel consumption and to direct it to the next target of interest in Kuiper Belt. Even for more orbiter missions!

At first glance, above plan reserves substantial amount of credit to itself comparing to other space missions (even Cassini, which was left to die with a death-dive to Saturn) nearby. But what about the corresponding fuel strategy?

Cassini Spacecraft
The Cassini Spacecraft. Source: here, Credit: NASA/JPL-Caltech

Fuel Strategy

If you are planning to launch a heavy spacecraft, send it billions of miles away within few years and organize several different and complicated tasks while needing energy to run couple of systems and send billions of bytes of data back to Earth; you need to be very careful how you maintain and preserve the energy for your vehicle.

First thing to note is that, as your spacecraft is going further away from Sun, your chances of using solar power is getting less; which is zero for a Pluto mission. So the setback occurring with this disadvantage is that, you have to carry big amount of fuel (mostly for slowing down) which makes launching and cost reducing harder.

Similar setbacks were valid for New Horizons and an RTG (Radioisotope Thermoelectric Generator) solved this problem. But this time similar plan for launching can not be processed since you’ll have at least twice as heavier spacecraft than New Horizons and will need more power to launch.

While combination of more effective traditional and RTG fuel strategies making sense to researchers for an orbiter or lander mission, those plans inrease the travelling time. According to predictions on the first 2 projects touched above, it’s more than 10 years. Even longer than the only Pluto mission realized!

Radioisotope Thermoelectric Generator
Diagram of the RTG used on Cassini Spacecraft. Source here, Credit: NASA

An Alternative Option: A Fusion Driven Spacecraft

While it’s still in process of development and not a ready-to-launch method, the Direct Fusion Drive Concept referred above, which derives energy via fusion power, is also an option. And what the project claims to fulfill is promising: To deliver a spacecraft more than 1000kg weight in about 4-6 years to Pluto. What’s more, they promise more than a thousand times of power dedicated to Lander-Spacecraft-Earth communications in long term. Even such lander vehicle can have powerful drilling options.

Above sounds extremely exciting and we can’t wait to see the day when above concept is near the mark.

Future Pluto Missions – A Conclusion: What Might Future Bring?

So in any case, what above suggests is that one way or another, we will need to visit Pluto again. We have to go back! And in addition, it suggests that the next visit to Pluto should at least be a long term orbiter mission.

But when can that happen? How much time should we wait to see Pluto again?

Since the only space agent planning or getting involved in different Pluto missions is NASA, that’s the agency holding the answers.

NASA usually plans assessments for the next 10 years in the beginning of the decades and clarifies the missions and the calendars in the earlier 2-3 years. In case any future Pluto Missions happen to be concluded and turned into real projects, we will have to wait till 2022-2023. And if no Pluto projects are realized, than 10 years more!

So let’s share and spread the word Pluto, keep up the support to make it happen again and asap!

What if we return to Pluto?


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