Five years ago, the world paused for a moment to admire the view of a distant world called Pluto. Its discoverer, Clyde Tombaugh wasn’t around to see the spectacular New Horizons views of the planet he discovered in 1930. But, in another sense, he WAS there with the rest of us.

A few grams of Clyde’s ashes fly on the New Horizons spacecraft that flew by his planet. So, for a collective moment, we explored Pluto with its discoverer and the team of scientists he inspired.

I’ve often wondered what Clyde would think of Pluto, up-close, and personal. I only met him a few times. He was a man with a great sense of humor and humility about his accomplishment. So, I imagine that he’d love it all. It would have been cool to have him on the science team as New Horizons flew by. His family members attended the flyby festivities in mid-July 2015 and celebrated the mission.

A Virtual Pluto Celebration

Today, we are in a very different world, one where a pandemic has closed us off to social gatherings like the one we all experienced at “mission control” at Johns Hopkins Applied Physics lab half a decade ago. Instead of meeting to talk over old times at Pluto, now we have to do it virtually.

So, instead, let’s imagine a circle of scientists sitting here with us. They’re reminiscing about the amazing mission to Clyde’s world. I asked a collection of New Horizons researchers to do exactly that. What did they learn about Pluto? If they could take Clyde on a guided tour, what would they show and tell him about Pluto?

Show and Tell for Clyde

Obviously, the first thing to show him would be heart-shaped Tombaugh Regio area of Pluto. It became THE ‘iconic’ view of the planet from the beginning of the flyby. That image changed forever how we saw that distant planet. Its icy terrain and lobe-shaped Sputnik Planitia section show glaciers butting up against mountains of water ice. Those features would likely excite Clyde. Those who knew him would be expecting him to crack a few puns to celebrate the occasion.

But, he might also be touched by other views. The most telling and effective image of Pluto is a view of its atmosphere and surface together. It encapsulated the planet, its atmosphere, and a feeling.

For Anne Verbiscer, a member of the New Horizons team, that’s the view she would share with him. “I’d show him that image taken at twilight,” she said. “I was reduced to tears when I saw it. I’ve had the same reaction to only one other planetary image returned by a spacecraft…it was the first image of Enceladus taken by Cassini for which I had done the “commanding”. Enceladus was in eclipse (behind Saturn), so I had very little information to use to set the exposure time correctly. I was sure that the image would either be black or over-exposed. When that image arrived on the ground, I saw that it was perfect, and yes, I sobbed, just like I did when I saw Clyde’s amazing world in all its glory on that September weekend in 2015.”

That view reminds all of us of the strange beauty of planetary exploration. There’s always something new to be seen, and when the exploration ends, there’s much to learn from the data collected. “I would show Clyde that image of Pluto at twilight (the one with the bottom of Sputnik Planitia in the foreground, the mountains rising above the limb, and the hazes above the horizon)….. and just drop the mic,” said Anne.

Clyde’s Surprising World

Principal investigator Alan Stern, not often at a loss for words, finds it hard to say what surprised him most about Pluto. “Before the flyby I might have not been surprised to find one of these: an interior ocean, or blue skies, or bladed mountains, or vast glaciers, or cryovolcanoes, or a paleolake,” he said. “But we found them all! And that is the most surprising aspect to me. That is, just how incredibly complex and diverse and frankly amazing as a scientific wonderland that Pluto turned out to be.”

To give you an idea of what amazed Alan and the others, take a look back in time. Clyde’s view in 1930 was of a small dot. That’s about all any of us can see, even with the best ground-based telescopes Even a high-resolution Hubble Space Telescope view showed a bland surface with a few bright and dark areas. No details of what was to come.

A Surprising World

New Horizons showed that every region on Pluto has something different on it, with some features unique to that world alone. Five years later, after much study and analysis, all that geology tells us something we didn’t know about the planet before the spacecraft went by: it’s not a dead world. “It shows the action of a wide range of planetary processes,” said Hal Weaver, another team member and long time planetary scientist. “That includes some that happened long ago, and others indicating ongoing activity into the current epoch.”

In other words, Pluto is alive. That’s a surprise, even today. And, that’s what Hal would tell Clyde first. If he could go to Pluto on a guided tour, the first place Hal would land would be Sputnik Planitia. “It’s responsible for Pluto’s “mojo”,” he says. “Especially its periphery. And, it’s part of the region named for Clyde! And, I’d bring along his extended family, too!”

Pluto and the followup mission to Arrokoth have accomplished another amazing feat. Those flybys prove the outer solar system isn’t what people expected it to be. “Pluto and Arrokoth have showed us that the Kuiper Belt is so full of surprises and revelations about the formation and evolution of the solar system,” said Paul Schenk, of the Lunar and Planetary Institute in Houston. “Going back to the Belt should be a high priority, to look at small, medium, and large-sized bodies and find out what happened there in the early days of our solar neighborhood.”

Beyond Clyde’s World

Nowadays, New Horizons is far beyond the Plutonian system. A few years ago, it explored Arrokoth, which is another Kuiper Belt object. It has other tasks ahead of it, including possible visits to new worlds. Its story is really one of opening the exploration of the third regime of the solar system. We’ve explored the inner solar system, the “middle” solar system of the gas and ice giants, and now the distant regime is open to our view.

Indeed, the exploration of the outer solar system really began with this mission. It is the first spacecraft to give us a true “up close and personal” look at the Kuiper Belt neighborhood. It’s only fitting that another spacecraft should make its way out there, to follow up on what New Horizons started.

Team member Kelsi Singer pointed out that there would be much to explore. “If we could go back with a spacecraft that orbits Pluto [instead of flying by], we could learn if Pluto has an ocean beneath its icy shell,” she said. “We could also further investigate how all its unique features formed. Of course, a lander or rover would be fabulous, but we have much to learn from an orbiter, first.”

Celebrating a Milestone with Clyde

Pluto and its exploration five years ago sparked our imaginations. It opened our eyes to an alien world. And, it shows us that preconceptions about planets are meant to be shattered. If New Horizons does nothing else, it will have shown us to expect the unexpected at every turn.

Alan Stern, who waited many long years for that exploration, working with some of the best scientists in the solar system, would just as soon be out there in an orbiter right now. He and a continuing team of scientists want to follow the trail that their spacecraft blazed.

And, if he could take Clyde along with him on that trip, he would. “I’d tell Clyde, who I knew, that he discovered an amazing world that has literally revolutionized our knowledge of planetary science in multiple important ways, and that in my view, we now know that in Pluto, the solar system saved the best for last!”