While New Horizons was wending its way on its long voyage, a panel of astronomers downgraded Pluto to a “dwarf planet,” which is to say a second-class planet (2).
Then, in July 2015, New Horizons conducted its flyby of Pluto and its five moons. Pluto, the former planet and current dwarf planet, was revealed to be a fully realized and complex world, with mountains made of dense water ice, plains made of solid nitrogen, glaciers, craters, and what appeared to be recent geological processes (3).
It was not, as many believed, a rocky ice ball, inert and dead, as characterized much of the nearby Kuiper Belt.
After a flurry of images of Pluto and its moons, particularly its largest satellite Charon, New Horizons left off sending pictures in favor of data that was garnered by its suite of scientific instruments. But then, on Labor Day weekend, New Horizons sent a batch of new images. These images have scientists almost literally reeling (4).
The new images reveal a landscape on Pluto that is as diverse as anything seen elsewhere in the Solar System. Mountain ranges rise up next to plains. Nitrogen ice flows, similar to glaciers on Earth, flow out of the mountains and into the plains.
Valleys were spotted, likely carved out by ice flows similar to how rivers create valleys on Earth. Smooth landscapes are shown right next to regions that are pockmarked with craters, suggesting recent geological activity that likely smoothed over impact craters in some regions,
Then, There Are the Dunes
Scientists believe that there may be dunes on Pluto, something that would be remarkable considering how thin the dwarf planet’s atmosphere is.
On Earth, dunes exist in the desert or on beaches and consist of sand that has been piled up by the wind. Does this mean that Pluto once had a thicker atmosphere? Scientists are still debating.
The exciting part of the news is that the best is yet to come. Because of the slow speed of transmission over the gulf of billions of miles, New Horizons is going to spend the next year unloading its treasure trove of data as it voyages into the Kuiper Belt, that ring of ice and rock that surrounds the solar system beyond Pluto.
No one knows yet what remains in the space probe’s computer storage waiting for scientists to study and wonder about.
In the meantime, the voyage of New Horizons is not over. The spacecraft remains sound, and it has enough power to last for several years. However, the space probe only has a little bit of maneuvering fuel left, so mission planners have to pick its next target with care. New Horizons also needs a little bit more funding.
Subject to review, scientists have focused on a distant Kuiper Belt object called 2014 MU69 (5), though to be 30 miles in diameter and therefore larger than the typical proto-comet thought to inhabit the region.
2014 MU69 is about a billion miles beyond Pluto. If all goes well, New Horizons will soar by it in early 2019. The final review and a decision on extra funding will be made in August or September of 2016.
Beyond the Kuiper Belt, New Horizons will eventually enter interstellar space, which only the two Voyager probes, as well as Pioneers 10 and 11, have either done.
It may be able to gather data about the Heliosphere (6), a bubble created by the action of solar wind against hydrogen and helium gas of interstellar space along with the solar magnetic field if its power supply has not run out, around the year 2026.