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December 6, 2019

The PI's Perspective: What a Year, What a Decade!

New Horizons is healthy and performing well as it flies ever onward, at nearly one million miles per day! This month we're collecting new data on the Kuiper Belt's charged particle and dust environment, and observing two distant Kuiper Belt objects (KBOs) to learn about their surface properties, shapes and rotation periods, and to search for satellite systems.

Much more is in store for this mission, but as this year and decade conclude, I want to look back and take stock of where we have been.

In the decade of the 2010s, Pluto, the most distant planet known at the dawn of the space age, was finally explored! Here, our team celebrates the news of New Horizons' successful flight through the Pluto system on July 14, 2015. (Credit: NASA/Bill Ingalls)

For New Horizons, 2019 began with a major mission milestone: the first-ever close up and personal exploration of a KBO. That target, originally known as 2014 MU69, is now the farthest world ever explored – more than a billion miles beyond Pluto!

And, if you hadn't heard, last month MU69 finally received its official name: Arrokoth, a Powhatan/Algonquian Native American word for "sky," which the New Horizons team chose. I love this beautiful name, and the way it beautifully honors both the state of Maryland, where so many Powhatans lived and where New Horizons was build and is operated from!

With data from the Arrokoth flyby – which will continue coming back to Earth through all of 2020 – we've already learned an amazing amount about KBOs that could never have been gleaned from Earth-based telescopes; not even the powerful Hubble or the much anticipated James Webb Space Telescope set to launch in 2021. Most importantly, in my view, we discovered that Arrokoth, a "contact binary" consisting of two independent lobes that joined gently, appears to have formed with the unmistakable characteristics of "local cloud collapse" models of solar system formation. These models, really just computer simulations before New Horizons revealed Arrokoth, posited that individual planetesimals – the building blocks of planets – formed from material in their immediate neighborhood, rather than from collisions of far-flung material as 20th century computer simulations predicted. Results from this flyby have led to a major advance in understanding the origin of the planets of our solar system.

The first results from the flyby of 2014 MU69, now officially named Arrokoth, graced the cover of Science in May 2019! (Credit: Science/ NASA/Johns Hopkins Applied Physics Laboratory/Southwest Research Institute/Roman Tkachenko)

The flawless flyby of Arrokoth and its many discoveries not only made 2019 a banner year for New Horizons, it also marked completion of the second major task (after exploring the Pluto system) that the mission was conceived to accomplish in the early 2000s, when the first Planetary Decadal Survey ranked it as a top funding priority. So it's appropriate this December to look back and celebrate the work of our mission and our team in carrying out this challenging exploration.

And as the decade of the 2010s ends, I also want to reflect on how much the mission has accomplished over the past 10 years. As 2009 closed out, New Horizons wasn't even halfway from Earth to Pluto – and Pluto remained just a dot in the distance to every telescope humankind had ever built. Halfway through the decade though, in the summer of 2015, New Horizons transformed Pluto and its system of moons from points of light into real worlds.

And what worlds we found! With our Pluto discoveries we can rewrite the textbooks about how complex and how geologically active small planets can be. From its convecting nitrogen glaciers and cryovolcanoes to its hazy atmosphere and the watery ocean that we now suspect lies beneath its icy crust, Pluto astounded us. So much so, in fact, that planetary scientists want new missions to orbit it and to study more of its dwarf planet kin across the Kuiper Belt. And as the data from the Pluto system flowed back in 2015 and 2016, New Horizons was sent onward to explore the Kuiper Belt in a first extended mission that targeted the flyby of Arrokoth as its centerpiece and which continues to explore both the Kuiper Belt environment and distant KBOs and dwarf planets seen in our telescopes.

Behold Pluto (foreground) and Charon, as seen by New Horizons in enhanced color! (Credit: NASA/Johns Hopkins Applied Physics Laboratory/Southwest Research Institute)

Exploring Onward

So as we look forward to the 2020s, our team is planning the next few years for New Horizons. Starting next summer, we plan to use some of the largest ground-based telescopes and possibly the Hubble to begin a search for new KBOs to explore, both up close and in the distance. (We can't search until summer because that is when the part of the sky where New Horizons is going is in the darkness of the night time sky.)

We don't know how many KBOs we will discover or whether any will be within our fuel supply to reach for a final close flyby, but that's what these searches, in 2020 and again in 2021, will reveal. We'll keep you posted on our progress, but keep in mind that finding MU69 took more than four years using the world's largest ground-based telescopes and then the amazing Hubble Space Telescope.

Our science team is working on literally dozens of papers describing new results from both the Arrokoth and Pluto flybys, all of which we expect to be published in 2020. This bonanza of results will kick off with a set of three papers now under review to the prestigious journal Science and will be followed by 20 papers in Icarus, the most well-known research journal of planetary science, and over two-dozen review papers about the Pluto system in a 1,000-plus page compendium to be called "The Pluto System After New Horizons," which is on track for a late 2020 publication date.

Also up for 2020 will be new flight software loads to give New Horizons additional capabilities for exploration across the decade of the '20s.

But even before all that, the New Horizons science team will be reporting new results next week and next month the American Geophysical Union and American Astronomical Society meetings. We'll also be meeting this month with NASA's storied Voyager space mission team to plan how New Horizons and the Voyagers – the most distant spacecraft in the Sun's heliosphere and the first spacecraft to operate in interstellar space, respectively – can work together as a multipoint observatory of the very distant space environment.

Celebrations of New Horizons flybys, like this one marking Pluto's exploration at the Johns Hopkins Applied Physics Laboratory on July 14, 2015, engaged the public across the world! (Credit: NASA/Bill Ingalls)

As the 2010s close, we on the New Horizons team have much to be thankful for in this amazing decade of discovery highlighted by historic explorations of the most distant worlds ever encountered by spacecraft. We also have much to look forward to, as a new decade and new explorations dawn for New Horizons.

Well, that's my report for now. Have great holidays and a wonderful celebration of the new decade dawning in just a few weeks!

I'll write again early in 2020. Meanwhile, I hope you'll keep on exploring — just as we do!

–Alan Stern

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