A decade after NASA’s New Horizons spacecraft made history with its flyby of Pluto, the quest to unveil the mysteries of this distant world remains fraught with challenges.
The mission, which captured a stunning landscape of Pluto on July 14, 2015, answered many questions that had lingered since astronomer Clyde Tombaugh discovered the dwarf planet in 1930.
However, as is often the case in the realm of planetary exploration, the data collected poses even more questions about Pluto’s dynamic nature and its remote location in our Solar System.
Currently, the only resources available for scientists seeking to unravel Pluto’s secrets are the extensive archives from the New Horizons mission, which include over 50 gigabits of data, and observations from powerful telescopes on Earth and in space, such as Hubble and James Webb.
Yet, ten years after the historic flyby, there are no missions planned to revisit Pluto, and the prospects of one appear bleak.
In a typical scenario involving a stable NASA budget, scientists might expect to begin developing another Pluto mission within the next 10 to 20 years, advancing beyond existing priorities like Mars Sample Return and missions to explore Uranus and Saturn’s moon Enceladus.
But these are not typical times.
The administration of President Donald Trump has proposed significant cuts to NASA’s science budget, jeopardizing not just future missions aimed at continued exploration of the Solar System, but also threatening the operation of active spacecraft, including New Horizons itself, as it ventures further into the Kuiper Belt.
These proposed budget reductions have led to a decline in morale within NASA and the broader space science community.
With a slashed budget, funding for research, including that which would allow scientists to analyze the wealth of existing data from New Horizons or conduct observations using telescopes, would also be severely impacted.
While the White House has expressed support for funding recently launched missions like Europa Clipper and Dragonfly, their proposed budget reflects a hesitancy to finance new projects focusing on locations beyond the Moon or Mars.
As a result, scientists find it challenging to envision the initiation of a new Pluto mission within the next 20 years.
Even if future administrations restore NASA’s planetary science budget, missions to Pluto are not likely to be prioritized.
The latest decadal survey by the National Academies has emphasized missions such as Mars Sample Return, an orbiter for Uranus, and an Enceladus lander as primary recommendations for NASA’s planetary science program through 2032, overlooking Pluto entirely.
This lack of attention to a sequel mission for Pluto is echoed by the scientific panel that considered the most recent decadal survey, which concluded that a subsequent mission to Pluto did not pass the thresholds for a technical risk and cost evaluation.
In the scientific community, there is consensus that a second mission to Pluto should be designed as an orbiter rather than a flyby, given the constraints and limitations experienced during the New Horizons encounter.
As New Horizons traveled at an incredible speed of nearly 31,000 mph (14 kilometers per second) and passed within 7,750 miles (12,500 kilometers) of Pluto, it could only capture glimpses of half the planet for a brief period.
The detailed observations that were made unveiled a complex terrain featuring a heart-shaped ice plain and water ice mountains, likely floating on a hidden ocean beneath its crust.
These findings pointed to Pluto possessing a significant source of internal heat, a surprising discovery that hints at a much more active world than scientists had anticipated before the flyby.
Questions about what lies beneath Pluto’s surface remain—what is the composition and thickness of the ice sheets, is there any activity from its suspected cryovolcanoes, and what lies on the unseen half of the planet?
To answer these pressing questions, scientists argue that an orbiter would be essential.
Some contributors to the New Horizons mission have proposed an outline for a conceptual mission to orbit Pluto, named Persephone, after the wife of Pluto in classical mythology.
Although this mission proposal has not yet been presented to NASA for consideration, it highlights the complexities involved in planning a dedicated mission to Pluto.
The initial Persephone design, released in 2020, suggests a launch by 2031 using NASA’s Space Launch System Block 2 rocket with an additional Centaur stage.
However, the outlined timeline may be overly optimistic, especially considering that this specific rocket is still in development.
If we envision a scenario where Persephone launches in 2031, it may take nearly 27 years for the spacecraft to reach Pluto, which would put its arrival in 2058.
Another design proposed by Alan Stern, the principal investigator for the New Horizons mission, aims to ensure the spacecraft carries enough propulsive resources to leave Pluto and potentially visit another object in the outer Solar System.
Both the Persephone and Gold Standard proposals envision utilizing gravitational assists from Jupiter, though alignment issues would likely delay any launches from 2032 to the early 2040s, effectively extending the time it would take to reach Pluto.
Previously, it took New Horizons nine years to reach Pluto, but an orbiter would need to carry significantly more mass for fuel and power to achieve the delicate maneuver of entering orbit around the dwarf planet.
Given Pluto’s weak gravitational pull, any spacecraft traveling too fast would simply pass by the planet, as New Horizons did.
The Persephone mission conceives the use of multiple nuclear radioisotope power generators and conventional electric thrusters—technologies that, while feasible, are still in early development stages.
The proposed mission could benefit from a nuclear electric propulsion system, which promises to significantly cut flight times to Pluto while enhancing communication capabilities.
The use of a modest 10-kilowatt nuclear reactor for electric thrusters could potentially reduce the overall journey by 25 to 30 percent and expedite data transmission speeds.
Nevertheless, funding for advanced nuclear propulsion research is under threat due to the budget proposals by President Trump’s administration.
While SpaceX’s Starship may possess the ability to launch missions to the outer Solar System, it remains to be seen whether its capabilities would be a viable alternative for a future Pluto mission, especially given it has not been extensively studied for this purpose.
As for costs associated with such missions, the Persephone concept is estimated to run around $3 billion—excluding the likely launch price of over $1 billion if a specific solution is required for the journey to Pluto.
Additionally, developing effective nuclear propulsion systems would also incur significant expenditures, potentially running into the billions.
This scenario suggests that the span between the first exploration of Pluto by New Horizons and any second visit may exceed 50 years, mirroring the hiatus observed between the Voyager spacecraft’s flybys of Uranus and Neptune.
As such, scientists appear to be bracing themselves for a lengthy wait—and perhaps contemplating the implications on their own lifespans—as they remain eager for a second exploration of one of the Solar System’s most captivating worlds.
image source from：arstechnica
