To Pluto and Beyond: Animating New Horizons’ Flight Through the Pluto System

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Stuart Robbins

An exhilarating, pioneering journey came to fruition on July 14, 2015, as NASA’s New Horizons spacecraft made its successful flight through the Pluto system, recording 60 gigabits of data that it is beginning to send to Earth. I’m Stuart Robbins, a research scientist at the Southwest Research Institute in Boulder, Colorado. While I only came onto the project relatively late – in 2012 – I’ve been able to interface with many different groups and people on New Horizons because my primary role was in planning.

The New Horizons mission is one of opportunity, not just in exploring a world in a region to which we’ve never been, but also for people who have a variety of backgrounds, interests and skills. One of my hobbies has been exploring computer-generated images and animations, and I volunteered to create the fly-through animation on this page.

The Pluto system as NASA’s New Horizons spacecraft saw it in July 2015. This animation, made with real images taken by New Horizons, begins with Pluto flying in for its close-up on July 14; we then pass behind Pluto and see the atmosphere glow in sunlight before the sun passes behind Charon. The movie ends with New Horizons’ departure, looking back on each body as thin crescents.Credit: NASA/JHUAPL/SwRI, Stuart Robbins


I strive for realism, so my first step was to build an accurate Pluto system within a 3-D environment. I used the latest data on Pluto’s orbit, its obliquity (how its pole is tilted relative to its orbit), and the orbits of all the known moons to create the system in software. I then “attached” a camera to the latest trajectory information so it would be as if you had a seat on New Horizons, watching Pluto as you zoomed past. I also worked on the lighting so that even the shadows as the spacecraft passes are at the correct angles, and the crescents during departure are at the correct positions.

In my original version, each frame (1/30th of a second) represented one minute of real time, and the field of view was that of the Long Range Reconnaissance Imager (LORRI), New Horizons’ eagle-eyed, black-and-white camera that gives us our closest views.

Unfortunately, the result was cinematically questionable, at best, because of the very brief time that the spacecraft gets its best images and the extreme change in distance between the spacecraft and planetary system over the course of July. I needed an alternative.

The final result was made differently: First, the timescale had to be variable. The final product goes from one second of movie time equaling 30 hours at the beginning and end, to one second of movie time equaling 30 minutes for the closest-approach section.

Second, the field of view could not remain as LORRI if the trajectory were to be realistic. I varied the field of view so that you can see the whole system at the beginning and end, and you can still see Pluto almost as a whole disk during the closest approach.

Third, the camera’s target – what’s in the center of the field of view – had to also vary. The movie starts and ends with the camera targeting the barycenter, the mutual point around which Pluto, Charon and the other four moons orbit. As the movie appears to zoom in for the Pluto flyby, the focus shifts to Pluto itself, and then it moves off Pluto so that it does not appear as though you are about to crash into the surface nor fly through the planet. The camera target remains on Pluto for the solar occultation – when the sun passes behind it – and then moves back to the barycenter for the solar occultation by Charon.

Fourth, the small moons – Styx, Nix, Kerberos and Hydra – were simply too small and faint to be seen to-scale. So I enlarged them by a factor of 5 and brightened them so you can at least see the two larger ones (Nix and Hydra), and I drew in their orbital paths.

Beyond that, everything about the movie is accurate: The Pluto hemisphere we see on closest approach, the lighting and shadows, the atmosphere’s size (though its brightness has been increased), the orbits of the satellites, the colors are our best estimate for what your eye would see, and so on. In addition, this movie retains Celestial North as “up” so that there are no twists, turns nor odd reorientation during the flyby.

The final result is the system as New Horizons saw it at the beginning of July 2015, flying to Pluto for its close-up on July 14, complete with the best maps we have to-date. It’s an incredible look at system we are unlikely to revisit in our lifetimes – though we have the potential to visit other bodies farther still from the sun with the craft as it continues to reveal new horizons in our solar system.

Atmospheric Escape and Flowing N2 Ice Glaciers – What Resupplies Pluto’s Nitrogen?

 

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Backlit by the sun, Pluto’s atmosphere rings its silhouette like a luminous halo in this image taken by NASA’s New Horizons spacecraft. Image Credit: NASA/JHUAPL/SwRI

Hi, I’m Kelsi Singer, a postdoctoral researcher at the Southwest Research Institute, working on NASA’s New Horizons mission and specializing in geology and geophysics. One of my areas of expertise is impact cratering. That subject may not seem related to Pluto’s atmosphere or nitrogen at first, but let me tell you about research that New Horizons principal investigator Alan Stern and I conducted and published as a prediction paper before the flyby of Pluto.

New Horizons has returned striking images of both Pluto’s surface and its atmosphere. Pluto’s atmosphere is similar to Earth’s in that it is predominantly composed of nitrogen (N). But Pluto’s atmosphere is ~98% N, while Earth’s is only ~78% N. Pluto’s atmosphere is also considerably thinner than Earth’s with ~10,000 times lower pressure at the surface.

Kelsi Singer
SwRI Researcher Kelsi Singer

The nitrogen in Pluto’s atmosphere (in the form of N2 gas) is actually flowing away and escaping the planet at an estimated rate of hundreds of tons per hour. We also see what looks like flowing ice on Pluto’s surface in high resolution images made by New Horizons. The water ice (H2O) that we are familiar with on Earth would be completely rigid and stiff at Pluto’s surface temperatures, but ice made out of N2 would be able to flow like a glacier. So where does all of this nitrogen come from?

One possibility we tested was that cometary impactors could be delivering the necessary material. We explored several different ways that impacts from comets could bring nitrogen to the surface and atmosphere of Pluto and resupply the escaping nitrogen:

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1) Could comets hitting Pluto directly deliver enough N to Pluto’s surface and atmosphere?

2) Could these comets excavate or expose enough N2 ice from the near-surface layers on Pluto by forming impact craters?

—> The short answer is that none of these cratering effects seem like they could supply enough nitrogen.

In our prediction paper, we suggested the next most likely suspect for supplying this N is heat and geologic activity inside Pluto itself. This activity could process nitrogen out of Pluto’s rocky interior and get it to the surface. We currently have only a tiny fraction of the data back from the New Horizons flyby, but the fact that there are young-looking areas on Pluto hints at relatively recent geologic activity.

Stay tuned as we get more data back from the New Horizons spacecraft over the coming months, which will refine our estimates of Pluto’s atmospheric escape and provide more images of Pluto’s surface to assess the types and timing of geologic activity.

Images by NASA/JHUAPL/SWRI