Mohawk Valley Astronomical Society

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Pluto Revisited

by Perry Pezzolanella

Pluto revealed itself as a world beyond the wildest imagination with a giant nitrogen glacier, methane snow-capped mountains, towering mountains of water ice, methane ice dunes, deep canyons and rifts, cryovolcanoes, and a hazy atmosphere when New Horizons flew by on July 14, 2015. No one predicted that Pluto would be more diverse and active than Mars. With Pluto officially dubbed the “New Mars”, the big question is: When will we go back?

It was tough getting approval for a mission to Pluto, and designing a spacecraft that would function during the decade-long journey to a dim, frigid world. A flyby mission was the fastest way to encounter Pluto since there was no feasible way to place a spacecraft in orbit around Pluto. Times have changed as spacecraft are becoming lighter with miniaturized components making it possible to launch spacecraft faster and farther with the most powerful rockets available. The use of ion propulsion has proven that it is possible to maneuver sequential orbits; the Dawn spacecraft that orbited Vesta and then went on to orbit Ceres is proof. This type of electric propulsion, coupled with gravity assists using Charon, will allow a craft to orbit Pluto and explore its moons for an extended period of time. The gravity assists from Charon while orbiting Pluto would save propellant and make it possible to continuously change the orbiter’s track over Pluto. Several years in this adjustable orbit would allow close-up observation of intriguing surface features that New Horizons discovered such as the frozen nitrogen lake in the mountains, and exploring other features that were poorly seen.

The big bonus is that this same spacecraft would be able to leave Pluto any time to fly out to other distant Kuiperoids and go into orbit. This means that instead of pressing for funding and approval of a Pluto orbiter or a Kuiperoid flyby mission, it is now possible for one spacecraft to do both, which makes it more compelling to go back to Pluto and beyond. The spacecraft would be able to orbit Pluto close enough to sample the atmosphere using the ion propulsion, and the flexibility makes it possible to encounter all five moons at very close range. It is even possible to deploy a small lander or rover on Pluto. There could be nothing more exciting than directly exploring the surface of Pluto and seeing possible methane dunes, glacial fissures, icebergs of water ice within the nitrogen ice sheet or distant scenery such as valleys, craters, flow features, rolling hills or distant methane ice-capped mountains.

Another bonus is that by using Jupiter for a gravity assist, travel time to Pluto can be cut in half, possibly as little as seven years, making the large Kuiperoids Eris, Sedna, Quaoar, Makemake, Haumea, and Varuna reachable within 25 years. Since these large Kuiperoids do not orbit in the same plane as Pluto, it will not be possible to explore an additional Kuiperoid after one of these large Kuiperoid missions is completed, but it is excellent science to get the most out of Pluto, its moons, and one Kuiperoid. Launch opportunities that occur from 2025 to 2040 are being studied. It is also possible to use Saturn, Uranus, and Neptune for gravity assists, with the additional bonus of a close approach to Uranus and Neptune that has not been seen close up since the 1980s.

Thanks to the improvements in technology and propulsion, it is now possible to design a mission using a spacecraft no larger than New Horizons that will return to Pluto for an extended stay along with one or more of the Kuiperoids. This is a lot of exploration for the price of only one spacecraft. We have the desire and ability, now we only need the funding and approval. Pluto beckons. We will return this time to hang out for awhile for a bit of sightseeing and exploring.