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Friday, July 31, 2020

Fifth Anniversary of New Horizons Pluto Flyby

Five years ago this month, on July 14, 2015, the New Horizons spacecraft made its historic flyby of Pluto, revealing a beautiful, complex planet and changing our view and understanding of that planet forever.

It is incredibly hard to believe that half a decade has passed since that amazing time, when Pluto became a rock star and made headlines around the world.

So many expected to find an inactive, dead world and were that much more surprised when instead, the spacecraft and its science instruments revealed a planet more geologically active than Mars, a planet with floating glaciers, windswept dunes, cryo-volcanoes, layers of atmospheric hazes, bladed terrains, mountains of water ice, interaction between surface and atmosphere, a likely subsurface ocean, and more than anything else, an iconic heart-shaped feature named Tombaugh Regio.

In the five years that have passed since then, numerous scientific papers have been written based on the data New Horizons returned. While it flew on past a second target and then proceeded to do more science studying the Kuiper Belt, planetary scientists, recognizing the flyby raised many more questions than it answered, have already begun advocating for returning with an orbiter.

An orbiter is the logical next step because it will be able to map the whole planet and provide high resolution images of the non-encounter hemisphere, which New Horizons was only about to image in low resolution.

Analysis of data returned by New Horizons seems to indicate Pluto not only harbors a subsurface ocean but likely has had that ocean since its formation four billion years ago. This puts Pluto in the growing category of ocean worlds in our solar system—worlds such as Ceres, Jupiter’s moons Europa and possibly Ganymede and Callisto, Saturn’s moons Enceladus and Titan, and Neptune’s moon Triton.

It may be that we need to recognize more subcategories of planets, specifically, these ocean worlds, any of which could possibly harbor microbial life and therefore completely alter our notions of what constitutes a star’s habitable zone.

The Pluto flyby was an exciting, thrilling accomplishment that stands in stark contrast to the troubled times we face now. But that also makes it a statement of hope, an Apollo moment, when people working together persevered in a long term effort that took a decade and a half to get to launch and then nearly another decade to reach its target. It is an inspiring achievement of people coming together, working with limited resources, building an extremely efficient spacecraft, and cooperating to quickly address any difficulties along the way. Flying a piano-sized spacecraft to a small, distant planet took precision, intellect, collaborating and problem solving—skills much needed around the world right now to address the various crises that plague this planet.

Beautiful Pluto inspired and gave hope to so many people. This mission stands as a tribute to the good people can do when they come together to work toward a difficult, ambitious goal.

Personally, I continue to hold the faith that scientists will succeed in returning to Pluto with an orbiter and that this return will be in my lifetime and the lifetimes of the many people who worked on the New Horizons mission and those who were enthralled by it.

For those interested, there are two new compilations of New Horizons' findings at Pluto. One is an e-book by Astronomy magazine, titled The Strange, Icy World of Pluto, which is available as a PDF for download at and an academic textbook coming out next year titled The Pluto System After New Horizons, which is available for order at .

Thursday, July 9, 2020

"The Pluto Perspective: Memories of an Amazing Encounter"

This blog entry, with retrospectives written by members of the New Horizons team, celebrates the fifth anniversary of the spacecraft's Pluto Flyby on July 14, 2015.

Wednesday, July 8, 2020

To Pluto and Beyond with Alan Stern

This Planetary Society radio interview with New Horizons Principal Investigator Alan Stern commemorates the fifth anniversary of New Horizons' Pluto flyby.