Rewriting the Playbook on Pluto

Richard Binzel is a professor of planetary science and joint professor of aerospace engineering at the Massachusetts Institute of Technology, as well as a member of the original “Pluto Underground” that struggled for more than two decades to bring a Pluto mission from dream to reality.

Through all the years of planning and conducting the New Horizons mission to Pluto, one thing was certain: we were going to rewrite textbooks based on what we found. And, boy oh boy, Pluto has not disappointed!

Plans are now underway to rewrite the granddaddy textbook of them all, “Pluto and Charon,” a scientific compendium of chapters covering everything known about the Pluto system when the book was published in 1997. I was fortunate to be one of the 50 collaborating authors (practically the entire Pluto community at that time) who came together to publish this volume as part of the Space Science Series of the University of Arizona Press. Planetary scientists Alan Stern (Southwest Research Institute) and David Tholen (University of Hawaii) edited “Pluto and Charon,” which, more than any other work, helped us to set our science objectives for New Horizons.

Book cover Pluto and Charon
“Pluto and Charon,” published in 1997, University of Arizona Press. Credit: Google Books

I’m familiar with Space Science Series textbooks at all levels, having become general editor of the series in 2000 and producing 10 volumes so far. (My predecessor and series founder, the late Tom Gehrels, prolifically produced 30 volumes.) These books are not for the faint of heart! Each is written for the level of a beginning graduate student who has completed at least a bachelor’s degree in physics, chemistry, planetary science or other intersecting field. My job as general editor is to carefully select the individual book editors and challenge them and their chapter authors to write what we know, how we know it, and where we are going in the future.

As a member of the New Horizons team, I am pleased that we are able to announce a new Space Science Series book, “Pluto After New Horizons” (as we are informally calling this sequel), that will begin taking shape in 2018 with a target publication date in 2020. That may seem like a ways in the future, but to those of us trying to make sense of all that the New Horizons data are telling us, that date seems to be coming way too fast. Mission Principal Investigator Alan Stern will again head the editing team and I will be joining him, with additional editor slots to be named later.

The challenge to construct “Pluto after New Horizons” is daunting. We have to discern and decode, as best we can, what the massive returned data set is telling us. In fewer than 30 chapters we have to cover topics ranging from the interior of Pluto and its surface processes, to its atmosphere and its near-space environment. And we can’t ignore Pluto’s largest moon, Charon, and the system of smaller satellites Styx, Nix, Kerberos and Hydra, who each need their story told.

With no mission to Pluto in the immediate forecast, the foundation of knowledge we build into this book will probably reign for decades. And just as “Pluto and Charon” in 1997 was the scientific foundation upon which mission plans were built with New Horizons as the capstone, we hope to make “Pluto After New Horizons” a textbook that lays the cornerstone for what will become the next era of Pluto spacecraft exploration.

Richard Binzel and Alan Stern with the 1997 book “Pluto and Charon,”
Richard Binzel (left) and New Horizons Principal Investigator Alan Stern with the 1997 book “Pluto and Charon,” which the mission team used more than any other text to form New Horizons’ science objectives. Plans are in the works for a sequel, tentatively titled “Pluto after New Horizons,” that would set the stage for the next generation of Pluto explorers. Credits: SwRI/Cindy Conrad

Processing Pluto’s Pictures

This week’s blog comes from Tod Lauer, a research astrophysicist at the National Optical Astronomy Observatory in Tucson, Arizona.

New Horizons Principal Investigator: “Lauer! We’ve got to have full resolution! Now!”

Me: “I’m pushing the images as hard as I can – any more and the pixels will blow apart for sure!”

Okay, the New Horizons Pluto encounter didn’t quite play out that way, but the science team really did want to get the most out of all the images of Pluto and its moons that we could, and often, as quickly as we could. I’m Tod Lauer, an astrophysicist who mainly works on stuff far beyond our galaxy. But I also love tough imaging challenges, and I enjoyed working with New Horizons as a sort-of utility image-processing engineer.

A few summers ago I wrote to New Horizons Project Scientist Hal Weaver on a whim to ask about the search for hazards to the spacecraft as it entered Plutonian space. Hal kindly replied with a note describing the capabilities of the New Horizons spacecraft and a report describing the search in detail. New Horizons co-investigator John Spencer, who was leading the hazard detection effort, also joined in. I was incredibly intrigued by the task: Search for unknown faint sources close to Pluto, which was embedded in an incredibly crowded field of stars (the heart of the Milky Way!), using heavily compressed images with the optical blur-pattern of the camera varying significantly from exposure to exposure – all on a critical timeline. I offered one approach, which led to me joining the “Crow’s Nest” crew that John and Hal assembled to search for hazards in the distant-encounter images. This work in turn led to an opportunity for me to help out with the encounter images as well.

Pluto's moons
In these simulated images from New Horizons’ Long-Range Reconnaissance Imager (LORRI), I demonstrated an approach to the hazard search. The image on the left (prepared by New Horizons’ John Spencer) shows Pluto and Charon greatly over-exposed to capture faint moons hiding among the heavily crowded background of Milky Way stars. The image at right shows a model of the fixed stars subtracted to reveal the four known small satellites of Pluto. This approach worked extremely well for the actual search. Credits: NASA/JHUAPL/SwRI

One task was getting the best resolution out of the images. Starting in April 2015, I worked to get the first glimpses of detail on Pluto and Charon as New Horizons’ long cruise across interplanetary space transitioned into the flyby itself. This continued up to closest approach and beyond as the images came back to Earth after the flyby. This work started with weaving a set of images of an object into a master image that preserved all the fine structure scattered about the image set.

Pluto
At left, a LORRI image of Pluto taken July 12, 2015, two days before closest approach. The image at right and others taken at the same time were combined as single image with a 2x-finer pixel scale and corrected for blurring to reveal many more details. Credits: NASA/JHUAPL/SwRI

The next step was to correct for the blurring due to the New Horizons optics. The final step required the greatest care – satisfying my fellow scientists on the team that they could trust the results for their research! The main objective was not to leave anything on the plate: It took hundreds of people working for two decades to get to Pluto, and it may be a while before we get back there. Every drop of information we can squeeze out of the images is immensely valuable.

LORRI images of Pluto's moon
The process in action, from left: Picture A is one of a set of four LORRI images of Pluto’s small moon Kerberos; in B, the four images have been combined to produce a 2x-finer finer pixel scale; C is the combined image corrected for blurring; and D has been interpolated to remove the blocky appearance and reveal new details about Pluto’s moon Kerberos. Credits: NASA/JHUAPL/SwRI

Another problem, which might seem surprising for a mission to Pluto, was dealing with the brilliant glare of the distant sun. On the way out to Pluto we had the sun to our back, while after close approach, we turned around to look at the night sides of Charon (and later Pluto), which had New Horizons’ cameras looking almost right back into the sun. Sunlight scattered into the camera strongly washed out the darkened hemisphere. The trick was to use a technique to capture how the scattered sunlight varied over a large collection of images, providing a way to build a perfect model of it for any image. With the sun canceled out we could see the night side of Charon softly lit up by “Plutoshine.”

Dark side of Pluto
At left is one of more than 200 LORRI images obtained to image the dark side of Charon by “Plutoshine;” the bright striations are sunlight scattered into the camera. At right, after all of the images are combined and corrected for the scattered light—Charon’s crescent and nightside are revealed! Credits: NASA/JHUAPL/SwRI

The best part of my experience with the New Horizons team was watching everyone work together to make the encounter a fantastic success. The hazard search concluded two weeks before the flyby, and having found nothing in our way, we stayed on our original, planned course to the Pluto system. From then on the tempo and energy level steadily rose as we flew ever closer to Pluto. For this astrophysicist, it was a treat to see the immense and diverse skills of the New Horizons team for planetary exploration brought to bear. If New Horizons were a ship, the team was its crew, with everyone smartly working at their stations but always keeping an eye on the big picture. Each of us used our talents in a unique way. No one wanted us to miss anything.

Tod Lauer
Tod Lauer
Credit: John Spencer

Behind the Lens at New Horizons’ Pluto Flyby

Today’s blog is from Henry Throop, a New Horizons science team member and senior research scientist with the Planetary Science Institute in Mumbai, India.

In a previous blog post, I wrote about software the New Horizons team used to image Pluto. Here, I’m going to talk about my work photographing the team itself.

We knew that New Horizons would be a historic mission scientifically. But we also knew it was important to document the human side of the encounter—the successes as well as frustrations. Just as we remember Neil Armstrong’s words and the shaky video from the surface of the moon, we knew that our team members’ activities would also form their own historical record.

APL, home of New Horizons mission operations in Laurel, Maryland, arranged for me and five other members of the science team to carry cameras as we worked. We were allowed access to the science working areas and public and press zones (though not mission operations, where flight controllers actually command the spacecraft).

While I’ve spent years photographing around the world, there was nothing more exciting than to point my camera at my friends and colleagues on this epic journey to the frontier of the solar system. Below are some of my favorite images.

Members of the Composition team compare their three independent analyses of the spectrum, which showed the very first detection of water ice.
Credits: NASA/JHUAPL/SwRI/Henry Throop

Although New Horizons had been in flight for over nine years, it was only two weeks before the Pluto encounter that we first detected Pluto with LEISA, the spacecraft’s near-infrared spectrometer. In the image above, members of the Composition team compare their three independent analyses of the spectrum, which showed the very first detection of water ice. Why three different models of the same thing? Just like an airplane has multiple altimeters, we wanted to be sure that we weren’t deceived by errors in any one model.

In the Payload Engineering room, shown above, Maarten Versteeg and Tommy Greathouse work with data from the Alice ultraviolet spectrometer
Credits: NASA/JHUAPL/SwRI/Henry Throop

In the Payload Engineering room, shown above, Maarten Versteeg and Tommy Greathouse work with data from the Alice ultraviolet spectrometer. This was taken 36 hours before Pluto close approach, and the instrument had sent back its very first spectrum of Pluto. Up until now, this instrument had been too far from Pluto to detect it.

In addition to the snacks keeping the team going, there are two New Horizons models here. At right is the detailed scale replica. But the more frequently used one is the small yellow model on the speakerphone, marked with the rotational axes we use to point it. A typical observation might be “Point +X toward Pluto, roll -Y to north, and then do a 30-degree scan around -Z.” We used models like this frequently when planning observations.

New Horizons team woke up earlier than normal to get our eyes on the highest-resolution global images that had been taken about 14 hours earlier
Credits: NASA/JHUAPL/SwRI/Henry Throop

On the morning of closest approach to Pluto on July 14, 2015, the New Horizons team woke up earlier than normal so we could get our eyes on the highest-resolution “global” images that had been taken about 14 hours earlier. Two members of the team worked overnight to process them in time for our team meeting at 5 a.m.

In the above photo, members of the science team see the young and un-cratered “heart” of the informally named Sputnik Planum close-up for the first time.

“phone home” signal was to be received around 8:52 p.m. EDT and was the emotional highlight of the encounter.
Credits: NASA/JHUAPL/SwRI/Henry Throop

On the day of encounter, New Horizons was busy observing Pluto, except for one short break to transmit a status update to the nervous team on Earth. This “phone home” signal was to be received around 8:52 p.m. EDT and was the emotional highlight of the encounter.

Setting up a few shots of the signal’s arrival, I was focused on my colleagues (in the black shirts above the railing), and I didn’t pay much attention to the man in the suit below them. But that is NASA’s Senior Public Affairs Officer Dwayne Brown, and it was his reaction that really made this shot!

Charon was discovered in 1978 by Jim Christy. Christy suggested the name “Charon” – but he pronounces it with a soft “Sh” instead of a hard “K,” in reference to his wife, Charlene.
Credits: NASA/JHUAPL/SwRI/Henry Throop

A day after flyby, we received new images of Pluto’s largest moon, Charon. Charon was discovered in 1978 by Jim Christy. Christy suggested the name “Charon” – but he pronounces it with a soft “Sh” instead of a hard “K,” in reference to his wife, Charlene.

Jim and Charlene were at the front of the APL auditorium as the images were revealed. While Jim watched quietly, Charlene was taking photos of it all – she told me she was e-mailing them to her family as fast as she could.

David Aguilar reacts to our front-page New York Times coverage on July 16, 2015.
Credits: NASA/JHUAPL/SwRI/Henry Throop

Our daily 8 a.m. science results meetings would often include an update on media coverage from David Aguilar, who led the team of writers assisting the science and public affairs teams with news and image releases. Here he reacts to our front-page New York Times coverage on July 16, 2015.

Over the course of seven weeks, I took close to 10,000 photos. I’m grateful to APL and the mission for allowing us to document our extraordinary time exploring Pluto—both from afar, and here on Earth.

Henry Throop
Henry Throop
Credit: Michael Soluri

 

Imaging the Encounter of a Lifetime

Jorge Núñez, a planetary scientist and engineer from the Johns Hopkins University Applied Physics Laboratory (APL), is the deputy systems engineer of the Long Range Reconnaissance Imager (LORRI) instrument on New Horizons. He studies the geology and composition of planetary surfaces using a variety of remote-sensing techniques. When not working on New Horizons or analyzing data from NASA missions, he also studies terrestrial analogs on Earth and develops new instruments for future planetary missions.

As a young child growing up in Colombia and later in the U.S., I learned about the nine classical planets in our solar system. Four terrestrial planets: Mercury, Venus, Earth and Mars. Four gas giants: Jupiter, Saturn, Uranus and Neptune. And then there was Pluto, at the edge of our solar system. All of the planets had been visited by spacecraft except Pluto; it was unknown and unexplored. I never imagined that I would be part of the first mission to see this mysterious, incredible world up-close.

As the deputy systems engineer for the Long Range Reconnaissance Imager (LORRI) on NASA’s New Horizons spacecraft, my role is to help make sure that LORRI is healthy, works properly, and that its images are acquired successfully. In addition, I help to make sure that commands sent to the instrument are correct.

LORRI is a panchromatic high-resolution telescopic camera composed of a telescope with an 8.2-inch (20.8-centimeter) aperture that focuses visible light onto a charge-coupled device (CCD). Similar to a grayscale digital camera with a large telephoto lens, LORRI imaged Pluto and its five moons from long distances during approach and mapped the surface of Pluto in unprecedented detail during New Horizons’ historic flyby on July 14, 2015. At closest approach, LORRI was able to image sections of Pluto’s sunlit surface at a resolution of about 70 meters, or roughly the size of a football field.

After New Horizons came out of hibernation for the last time, in December 2014, LORRI began to acquire a few images daily. During the months before the encounter, these images were used to help the spacecraft navigate toward the desired flyby location and help scientists refine orbit calculations of Pluto and its moons. In addition, LORRI was used to look for additional moons and potential rings that could have posed a hazard to the spacecraft. New Horizons was flying so fast, at approximately 31,000 miles per hour (14 kilometers per second), that a collision with something as small as a grain of rice could have been catastrophic.

As New Horizons sped closer, Pluto, which initially appeared as a small dot in LORRI images, grew to a system with multiple objects. The complex surface features on Pluto and its largest moon, Charon, came into better focus. Each LORRI image was better than the next. The team worked day and night to keep up with the data and images coming down with each transmission from New Horizons. LORRI images were posted on the New Horizons project website so the world could follow along in the excitement.

Mission science team
Mission science team members revel in seeing Pluto revealed by the LORRI instrument aboard New Horizons on July 13, 2015. Credit: Michael Soluri

On July 13, the night before closest approach, the last LORRI image before the encounter was transmitted to Earth. This was the best view of Pluto we would receive before New Horizons flew by Pluto. It became my responsibility and privilege to verify that the image came down properly before it was unveiled to the team and the world the next morning. When unveiled the next morning, the image became an instant icon.

Pluto
This LORRI image of Pluto was combined with lower-resolution color information from the Ralph instrument, captured just before the New Horizons spacecraft’s closest approach in July 2015. The view is dominated by the large, bright feature informally known as Tombaugh Regio – Pluto’s ‘heart’—which measures approximately 1,000 miles (1,600 kilometers) across. Credits: NASA/JHUAPL/SwRI

During the encounter of the Pluto system, LORRI worked flawlessly and acquired more than 1,800 images of Pluto and its moons during closest approach and flyby. Since the encounter, the stored LORRI images on New Horizons’ digital recorders have been coming down to Earth and will continue to come down through at least this September. They reveal a fascinating, complex world with a diversity of landforms like mountains made of water ice, and volcanoes and glaciers of exotic ice. More remains to be discovered.

And LORRI’s mission is not yet over! The LORRI team is now preparing for the flyby of the Kuiper Belt object known as 2014 MU69. If NASA extends the New Horizons mission to accomplish this flyby, New Horizons will reach 2014 MU69 on Jan. 1, 2019. LORRI will provide the first close-up observations of an object thought to represent what the outer solar system was like following its birth 4.6 billion years ago. More mysteries to be revealed by LORRI and New Horizons await!

Jorge Núñez
Jorge Núñez at the unveiling of Pluto images the morning of July 14, 2015, at APL

A Picture of Pluto is Worth a Thousand Words

Today’s blog is from Veronica Bray, a planetary scientist at the Lunar and Planetary Laboratory in Tucson. She specializes in comparing the surfaces of planetary bodies across the solar system, especially through the study of impact craters.

A spacecraft flies to Pluto, amazing images of this alien disk are sent back to Earth for us to enjoy, and suddenly scientists are telling us about what Pluto is made of—that it has different layers in its crust, that one part of the Pluto crust is weaker or stronger, or older or younger than another. How can that information be gained from photos?

Well, in part the answer is that many other kinds of data—like compositional and atmospheric spectra – were also obtained, but this blog post gives one example of how the New Horizons team is using the spectacular images to investigate the surface of Pluto. As my specialty is impact cratering, you know what I’ll be talking about.

When a comet or other object collides with Pluto, the speed of the impact is typically faster than a bullet. As a result, such collisions create an explosion that excavates a large hole in the surfacean impact crater. Depending on the size, speed and density of the impactor, as well as the near-surface properties of Pluto, the resultant craters can look very different from one another. As part of my work with the New Horizons team, I have been using the study of impact craters as a tool for investigating the physical properties of the Plutonian crust. I do this first by measuring the dimensions of different craters on Pluto from the Digital Terrain Models (DTMs), created from New Horizons images by my awesome team members! The figure below shows a topographic profile of the informally-named Elliot crater, whose namesake is the late Pluto researcher Jim Elliot of MIT.

Topographic profile, taken from a preliminary digital terrain model, with crater dimension marked
A) New Horizons image of Elliot crater, a ~ 56-mile (90-kilometer) crater in the informally-named Cthulhu region. The yellow line marks the path along which a topographic profile was drawn, from X to X’.
B) Topographic profile, taken from a preliminary digital terrain model, with crater dimension marked. D = crater rim-to-rim diameter, d=crater depth from rim tip to floor, Dp = width of central peak, Hp = height of central peak. The average crater wall slope, S, is calculated as d/W. Credits: Created by Veronica Bray using a profile from New Horizons’ Paul Schenk and New Horizons imagery from NASA/JHUAPL/SwRI

From this profile I can measure all the important dimensions, including:

Depth (d) and Diameter (D).   When measuring a newly formed crater, a lower depth/diameter ratio can point to a weaker or warmer target surface. The depth/diameter value (and the other crater dimensions listed below) is also affected by the gravity of the target body and the age of the crater, as craters tend to shallow with time. So, depth/diameter can also be used to gauge the relative age of the different craters on Pluto.

  1. The central peak height (Hp) and width (Dp). These can tell us about how much uplift of material from depth has occurred at the impact site. When I compare this ratio to the uplifts seen in other craters across the solar system, I can tell whether the Pluto near sub-surface is weaker or stronger than on other bodies. I can also compare central peak craters across Pluto: two craters of the same size with different central peaks might be telling me that the one with the larger peak was formed by a higher velocity impact, or that the Pluto surface is weaker or warmer in that location.
  2. The height of crater rims (measured from the surrounding terrain level). This offers indirect evidence of the extent of crater wall collapse. When comparing two craters of the same diameter, a lower rim height suggests that more collapse has occurred and might point towards the upper levels of the Pluto crust in that area being weaker than for areas with greater rim heights.
  3. The average slope angle (d/W). Although the walls of craters can be complicated, including scarps, terraces and scree slopes segments (all of which can provide their own information on the material strength and target structure), we can also gain knowledge from a more simple measurement: the average slope angle, as it is a proxy for the ‘effective’ coefficient of friction during the process of impact crater formation.
  4. Crater Diameter of ‘benched craters’ can be used to estimate the thickness of layers – as seen in the figure below – within the Pluto crust. This is an especially exciting crater dimension to study as it gives a specific value – the upper layer thickness. We can then start to hypothesize on why this layering is there. Is it deposition from the atmosphere, snowing down on the surface? Is it bombardment from the solar wind breaking down the upper layer of the crust to make a regolith, like we see on the moon?
New Horizons image of a possible nested crater on Pluto
A) Image of a mile (1.2 kilometer) simple crater on Earth’s moon. The wide bench on its interior wall has been used to infer that the moon’s surface in this area consists of a weak layer about miles (100 meters) thick, overlying a more resistant rock unit. Credit: Apollo Panoramic Photograph AS15-9287 B) New Horizons image of a possible nested crater on Pluto. This image has been reoriented so that the shadows within the crater are similar to the lunar example. North arrow indicates direction to the Pluto north pole. Lower row: Sketches of different crater morphologies produced when the ratio of crater diameter and the thickness of the upper weak layer changes. (From Melosh, 1996; after Quaide and Oberbeck, 1968). Credits: Created by Veronica Bray using an Apollo Panoramic photograph, a New Horizons image and diagrams from NASA/JHUAPL/SwRI

I’m currently measuring crater dimensions on Pluto and other icy bodies so that I can compare them to one another and also to existing measurements of craters on rocky bodies such as Earth’s moon. Once I have these measurements and the topographic profiles in hand, I can also use them to compare to my computer modelling results in which I simulate the impact process in various targets (different materials, different sets of layers, whatever I want). There are thousands of craters on Pluto waiting for me to measure them. I’d better get started!

If you would like to read more about how to use impact crater measurements to study the surfaces of moons and planets, I suggest the following references:

Bray, V. J., G. S. Collins, J. V. Morgan and P. M. Schenk (2008). The Effect of Target Properties on Crater Morphology: Comparison of Central Peak Craters on the Moon and Ganymede, Meteoritics and Planetary Science, Vol. 43, No. 12, pp. 1979-1992. PDF Here

Quaide, W. L. and Oberbeck, V. R. 1968. Thickness determinations of the lunar surface layer from lunar impact craters. J. Geophys. Res. 73:5247-5270. PDF Here.

Osinski, G. R. and Pierazzo, E. (2012). Impact cratering: Processes and Products. ISBN: 978-1-4051-9829-5, 330 pages, Published December 2012, Wiley-Blackwell.

Melosh, H. J. 1989 Impact cratering: a geologic process. 245 pages, Oxford University Press.

Veronica Bray
Veronica Bray
Credit: Ken Sterns

Planning for Pluto with GeoViz

Today’s blog is from Dr. Henry Throop, a planetary scientist with the Planetary Science Institute in Mumbai, India. He received his PhD in 2000 from the University of Colorado, Boulder. His areas of research include the outer solar system, the rings of Jupiter and Saturn, and planet formation in the Orion Nebula. He has been working with the New Horizons mission since 2002.

New Horizons traveled for 9.5 years to get to Pluto. But most of the spacecraft’s key Pluto system observations were taken within a single 24-hour period. How did we make sure that we get the best observations possible — to do the best science in those 24 hours? Well, it took a lot of planning.

When astronomers are using telescopes on the ground, observing is sometimes unplanned, and conditions vary as the night moves along. Perhaps the images from an object are particularly interesting, so we take more. Or the weather is changing, or an instrument is not working right, and we move to a new target or new instrument, improvising along the way.

But for the Pluto encounter, there was no possibility of this. With only a single day to gather the once-in-a-lifetime datasets about this new world and its moons, we wanted to squeeze in all of the observations we could. Single images, mosaics, wide scans, spectra, radio occultations and more—all had to balance out to maximize the overall science. The observations were packed so densely that we would have no time to effectively improvise in real-time. And, more importantly, with a 9-hour round-trip light time between New Horizons and the ground, it would simply not be possible to take some images, send them down, and then decide to take more observations from the most interesting area.

Instead, the entire encounter had to be sequenced in advance. Putting the observation plan together took several years of meticulous planning, and the final observing program was to be uploaded to the spacecraft about 10 days before encounter. About a week before flyby, that observing plan started executing—firing off a sequence of turns, snaps and scans that would execute the science program.

So how does the science team choose where to point? You might say, “Just look at everything!” But during the central 24 hours, our view of Pluto would be constantly changing: different distance, different face, different solar angle, and so forth. We needed some way to simulate what the view from the spacecraft would look like, and determine where we should aim our instruments. How much of Pluto could we see? What surface locations (longitude, latitude) would we be crossing over? What stars would be in the background? Which hemisphere of Pluto would be visible and at what resolution?

This is where one of my roles in the mission comes in. I am the developer and maintainer of GeoViz, which is the software tool the science team uses for planning observations. You can think of GeoViz as essentially a sophisticated and very accurate planetarium program – a ‘Geometry Visualizer’ – that shows the sky and planets as they appear on a given date. It gives you the view not as if you were standing on Earth, but as if you were on the spacecraft. Want to know exactly when Charon will pass behind Pluto? Just ask GeoViz to plot it. Need to know how many LORRI images will fit on a mosaic across Pluto at T – 3 hours? GeoViz will show you. Want to get a list of the bright stars that our Alice instrument will scan during a calibration observation, and make a movie of the scan? GeoViz will work this out as well. It is a web-based program to simulate observations, showing the geometry of the solar system, and how it fits in with the spacecraft’s various instrument fields.

My background is as an astronomer, not a programmer. But I and many astronomers spend much of our time as programmers: writing code to automate data analysis, perform simulations, or run instruments or mosaic images together. I started GeoViz as a way to automate figures I was producing for New Horizons’ Jupiter flyby in 2007. Since then I’ve been developing it into the powerful, general-purpose planning tool that it is now.

New Horizons GeoViz
Using GeoViz to simulate an observation of Charon with the New Horizons’ LORRI camera, a few hours before close approach to Pluto. Credits: NASA/JHUAPL/SwRI

GeoViz consists of about 40,000 lines of code. Most of it is written in a language called IDL (Interactive Data Language), which has historically been widely used in the astronomical community. (Python is coming on strong, however, and I’d probably write it in Python if I were to start it from scratch.) It uses PHP and Javascript / jQuery for handling the web side of things, and IDL for the back end. The numerical calculations – position of the planets, velocity of the spacecraft, and instrument rotation angles – rely heavily on a library of geometry and orbit routines known as SPICE, developed at NASA’s Jet Propulsion Lab (JPL). SPICE is a really critical part of the code, because it does computations that would be very difficult to implement reliably on their own. Many different parts of the New Horizons team use SPICE – for tour planning, archiving, science analysis, plus the visualization that GeoViz does – and using the common SPICE library assures that we all get the same results. Likewise, if the SPICE libraries are updated (for a new trajectory, for instance), then all of the groups can update their results at the same time.

What were the biggest challenges? The first was to keep it simple to use, while still adding the new features that the science team requires. GeoViz is widely used because it works well, and it has a clear user interface. There are hundreds of different options internally, but the interface design is kept clean enough so that it’s not overwhelming.

The second challenge was to keep it running. GeoViz doesn’t communicate with the spacecraft directly, and is not ‘mission-critical.’ But during the encounter the science team was using it heavily, and we didn’t want it to go down, nor did we want a newly added ‘feature’ to turn out to have unforeseen side effects. We addressed that by keeping two versions of it: a ‘stable’ version that was only rarely updated, and a ‘development’ version with the latest features.

Pluto scientists
At APL in July 2015, scientist Amanda Zangari (right) and I discuss a new orientation for Pluto’s pole in GeoViz. Credit: Richard Binzel

When I started working on New Horizons at SwRI, I was living in Boulder, Colorado, where much of the rest of the team was located. But my wife works as a diplomat, and her job takes her around the world. After being in Boulder for several years, we moved to Mexico, and then South Africa, and now we are living in India. Most of my work on the mission can be done remotely: with Pluto about 3 billion miles (5 billion kilometers) away, the fact that I may be on the other side of the Earth is a relatively small difference. For the flyby itself, I came back to the U.S. and spent two months working closely with my colleagues on the team. After ten years of working on the project – much of it remotely – I wasn’t going to experience the flyby over a speakerphone!

There were a lot of long nights at APL preceding the encounter and a few tense days as we closed in, followed by one of the most exciting moments of my life: listening with the world to Mission Operations Manager Alice Bowman, as she calmly polled her team of engineers before announcing the spacecraft’s successful passage through the Pluto system.

Now that I’m back abroad now, living in India gives me a great chance to talk about New Horizons, NASA, and Pluto to audiences around the world. I’ve given nearly a hundred public talks and lectures about the mission to audiences in Africa, Latin America and Asia. Some of the most rewarding talks were at rural schools in South Africa.

The science team members remain heavy users of GeoViz. It continues to be used post-flyby, not to plan observations, but now to help analyze them. (“Where was the spacecraft pointed for this image? Is that bright object Pluto’s moon Nix or a star?”) Working with the team has been one of the most rewarding experiences of my life – it’s amazing to think that all this planning paid off in getting us to Pluto. We really did it!

Henry Throop
Henry Throop

Pluto Flyby: The Story of a Lifetime

“You can report on history, or you can be part of it.”

This quote – from a colleague here at NASA – sums up what inspired me to take a giant leap from a digital newsroom to the mission operations center for the July 2015 New Horizons Pluto flyby. I’m Laurie Cantillo, and as media liaison in the Office of Communications at NASA, my mission is to tell the story of the agency’s planetary missions. As NASA’s media embed with the New Horizons science team, I had a front row seat to an unforgettable adventure.

Working in a makeshift newsroom last summer at the Johns Hopkins University Applied Physics Lab (APL) in Laurel, Maryland, we were at the epicenter of this historic journey, as new images and other data of Pluto and its moons were downlinked after a 4-and-a-half hour journey from the spacecraft. The energy in the room was electrifying when new data would hit the ground and scientists would gather around a computer screen to gape, interpret, and marvel about humanity’s first views of this strange, distant world.

Image of People Surrounding a computer
In the media room at APL, a familiar sight as new images of Pluto would come in each day. (seated left to right: Laurie Cantillo, John Spencer, Alan Stern. Standing left to right: Jeff Moore, Randy Gladstone, Ron Cowen, Andy Chaikin, Bill Lewis, Will Grundy, Maria Stothoff, Steve Maran. Credits: NASA/Bill Ingalls

Scientists, mission operations, engineers, and writers all worked insane hours – often 18-20 hours a day for months without a day off – catnapping on a conference room floor or in someone’s empty office. We drank a lot of caffeine and had pizza delivery on speed dial.

The most anxiety-producing period of the summer came the afternoon of July 4. While the nation was grilling hot dogs and preparing for fireworks, Principal Investigator Alan Stern burst into the newsroom saying, “We’ve lost contact with the spacecraft.” My heart skipped a beat as he hustled to mission control—it was all hands on deck. The spacecraft had recognized a problem and, as it’s programmed to do, switched from the main to the backup computer, going into what’s known as “safe mode.” Working around the clock and sleeping on the floor, the mission team raced against time to bring New Horizons back to the main computer, so the final command sequence for the flyby could be loaded.

At the same time, I worked with Stern and NASA officials into the night on a mission update that posted within just a few hours of the anomaly. I drove home long after the fireworks shows had ended, adrenaline-fueled in spite of exhaustion. Thanks to the mission team’s hard work, the spacecraft later returned to the main computer, and the big event was back in business. New Horizons had overcome what Stern later called our “Apollo 13.”

With the anomaly resolved, the science continued. A few days before closest approach; the lights were dim in our newsroom as planetary geologists puzzled over a large-screen image of Pluto that was still fuzzy but showing tantalizing signs of geology. The science team discussed the nuances of the light and dark features that made Pluto more interesting than the dull, cratered space rock many expected it would be. I raised my hand from the back of the room and offered, “Does anybody notice that bright feature has the shape of a heart?”

Pluto
This view of Pluto, captured just before the spacecraft’s closest approach, is dominated by the large, bright feature informally known as Tombaugh Regio – Pluto’s ‘heart’—which measures approximately 1,000 miles (1,600 kilometers) across. Credits: NASA/JHUAPL/SwRI

The scientists labored over a caption with a few specs and contextual quotes, and broke for lunch. Then it was my turn to add the storytelling, taking the numbers, acronyms and geological jargon and weaving them into a colorful narrative. I wrote a headline about the “heart” of Pluto, and soon after that Pluto went viral, far beyond the usual loyal community of space fans. Pluto was already beloved by many because – after its demotion by astronomers from planet to dwarf planet – it became the “little-planet-that-could.” But after it was revealed that Pluto had a “heart,” the story went mainstream, attracting global attention. In the summer of 2015, the world “hearted” Pluto!

The New Horizons mission became the perfect media storm. You had to be living under a rock to not know that America had a spacecraft exploring Pluto, a mind-bending 3 billion miles away. NASA, SwRI, and APL’s amazing communications, education and outreach teams further spread the news through social media, at NASA centers and museums, at Plutopalooza events and NASCAR races. People from all over the world took photos at dawn and dusk – simulating the amount of sunlight on Pluto – for #PlutoTime. We collaborated with Google on a July 14 Doodle. Images of Pluto were projected at Times Square. The group Bastille produced a video greeting, astrophysicist and Queen lead guitarist Dr. Brian May went backstage with the science team, and the band Styx traveled to APL, posing for photos with the New Horizons team, including Mark Showalter, who discovered Styx—one of Pluto’s moons. The media’s appetite was insatiable, and we were bombarded with hundreds of interview requests.

New Horizons Flight Controllers celebrate after receiving confirmation from the spacecraft that it had successfully completed the flyby of Pluto, Mission Operations Center (MOC) of the Johns Hopkins University Applied Physics Laboratory (APL), Laurel, Maryland. Credits: (NASA/Bill Ingalls)
New Horizons Flight Controllers celebrate after receiving confirmation from the spacecraft that it had successfully completed the flyby of Pluto, Mission Operations Center (MOC) of the Johns Hopkins University Applied Physics Laboratory (APL), Laurel, Maryland. Credits: NASA/Bill Ingalls

On the evening of July 14, the crowd at APL went wild as we received word that the New Horizons spacecraft was healthy and the mission was a success. On July 15 – the day after the flyby – the Pluto story was on the cover of more than 450 newspapers in multiple languages. Countless kids sent drawings of Pluto and wrote of dreams of being astronauts. Congratulatory messages poured in from people who said the mission inspired them at a time when there was so much bad news in the world.

Stephen Colbert and Neil deGrasse Tyson debated whether Pluto was a planet. Pluto became the subject of dozens of memes. My favorite (about 0:55 seconds in) personifies little Pluto as it eagerly anticipates the arrival of a spacecraft in that lonely part of the solar system. As New Horizons flies by, Pluto sheds a tear and its heart “breaks,” a nod to the different surface composition of each side of Pluto’s heart feature.

Nine months after the flyby, the New Horizons team continues to produce new images with analysis every week. Interest in the mission remains high; pictures of the “little-planet-that-could” are among the most popular features on NASA.gov.

Covering the New Horizons mission is an example of how NASA’s Office of Communication strives to bring you the stories behind the missions. Yes, it IS rocket science with mission design, data analysis and scientific information, but it’s even more about vision, leadership, perseverance, and celebrating the REAL heroes of our time.

Laurie Cantillo with Brian May
Laurie Cantillo with Brian May
Credits: NASA/Bill Ingalls

Mapping to Make Sense of Pluto

Today’s blog post is from Oliver White, a postdoctoral researcher in planetary science at NASA Ames Research Center in Mountain View, California. He studies the geomorphology and surface processes of planetary bodies in the outer solar system.

Looking at the surface of a planet or moon for the first time can be bewildering, particularly when confronted by a variety of terrains and landforms. This is certainly what NASA’s New Horizons team felt when we received the first close-up pictures of Pluto after the flyby in July 2015. None of us were expecting to see such a diverse range of landforms like mountains and glaciers of exotic ice on such a small, cold and distant world.

After flyby our challenge was to piece together the geological history of Pluto’s surface—that is, to determine what processes have formed and modified each terrain, and when these processes occurred relative to one another.

In order to accomplish this, planetary scientists create geological maps of the surfaces of distant bodies. The New Horizons spacecraft flew past Pluto at a range of several thousand miles/kilometers. As such, creating a geological map of a planetary surface like Pluto’s is more challenging than creating a map for one on Earth. Of course, we’re unable to walk around on Pluto and pick up samples in order to analyze what they are and how they have been processed. Instead, we must rely entirely on spacecraft images and other remote sensing data to create a Pluto map. For example, compositional data provided by the Ralph/Multispectral Visible Imaging Camera (MVIC) and the Linear Etalon Imaging Spectral Array (LEISA) are extremely useful for mapping Pluto. Knowing the composition of a unit helps constrain what physical properties it has and, therefore, how it likely formed and was modified over time. The compositional data are the closest we have to possessing an ice sample from each of the different terrains on Pluto.

Pluto Geologic Map
Geological map of the informally named Sputnik Planum and surrounding terrain on Pluto. Click on the map for a larger version. See image below for scale bar. Credits: NASA/JHUAPL/SwRI/Oliver White

The colored map shown above is just such a map that I have created for the region of the encounter hemisphere on Pluto that covers the huge nitrogen ice plains informally named Sputnik Planum and the terrain immediately surrounding it. The map shows New Horizons imagery of this area, overlaid with colors that represent different geological terrains, or units. The black and white image below shows the New Horizons imagery, along with latitude and longitude lines and a scale bar.

Pluto Mosaic
Mosaic of 12 New Horizons images obtained by the Long-Range Reconnaissance Imager on New Horizons at a resolution of 1280 feet (390 meters) per pixel, which was used as the mapping area. Credits: NASA/JHUAPL/SwRI/Oliver White

I have studied this area in great detail, and have defined each unit based on its texture and morphology—for example, whether it is smooth, pitted, craggy, hummocky or ridged. How well a unit can be defined depends on the resolution of the images that cover it. All of the terrain in my map has been imaged at a resolution of approximately 1,050 feet (320 meters) per pixel or better, meaning textures are resolved such that I can map units in this area with relative confidence.

By studying how the boundaries between units crosscut one another, I can also determine which units overlie others, and assemble a relative chronology (or timeline) for the different units; this work is aided by crater counts for the different terrains that have been obtained by other team members. I caution that owing to the complexity of the surface of Pluto, the work I’ve shown is in its early stages, and a lot more is still to be done.

My mapping project, which began only a few days after the flyby, is currently expanding across the rest of Pluto’s encounter hemisphere. Mapping a place as interesting as Pluto has been a highly engaging, thought-provoking and fun experience. When I was an undergraduate studying planetary science, filling in my first planetary geological map of a region on Mars with coloring pencils, I never imagined that a decade later I would be making the first geological map of this world that had been a tantalizing enigma for so long!

Oliver White
Oliver White with a model of the New Horizons spacecraft.

Mapping Pluto

Today’s blog post is from Ross Beyer, a planetary scientist with the Carl Sagan Center at the SETI Institute and NASA Ames Research Center in Mountain View, California. He studies surface geomorphology, surface processes, remote sensing and photogrammetry of the solid bodies in our solar system.

I’ve always loved maps, and I’ve always loved planets and space, and the idea of exploring new places – so getting a doctorate in planetary sciences seemed to flow naturally from my interest in space, planets and exploring. My job as a research scientist, exploring the solar system vicariously through robotic spacecraft for the last two decades, has been a joy. But it wasn’t until later that I realized my work with planetary images was also connected to my love of maps. And all of these things have come together with my work on New Horizons.

Pluto
This map of Pluto was made from all of the Long Range Reconnaissance Imager (LORRI) photos taken by New Horizons. Credit: NASA/JHUAPL/SwRI

After the February 2007 Jupiter flyby, I helped the mission team plan the Pluto encounter. New Horizons was going to fly through the Pluto system, as if the spacecraft was on a rail moving out from the sun. We couldn’t do loop-de-loops or any other complicated motions at Pluto; we were just moving through. However, we could pivot and point our instruments at Pluto and its moons Charon, Nix, Hydra, Styx and Kerberos, so we had to figure out that sequence of events. Our mission had to satisfy numerous specific scientific objectives, so we had to lay out a sequence of observations that used our time wisely as we zipped past. I was just one of the many, many people involved in that effort. It was hard work, frustrating at times, but ultimately very educational and also fun, as we tried (and I think succeeded in) arriving at a plan that captured a wonderful series of observations from all seven science instruments on New Horizons. Of course, I was most interested in the pictures that we were going to take!

When New Horizons flew by Pluto and Charon last July, it snapped many pictures of these new worlds for the first time. As a geologist and a photogrammetrist (someone who measures things from images), it is important for me to understand correspondences between the images: where do the higher resolution images belong amongst the images taken from farther away that show more area? How is one image related to the next? To answer these questions and more, we make something called a control network, and from that we can make maps.

A control network is made from finding control points between images. So if we have two images of Pluto, and we can identify the same feature in both images – say, a crater – then we mark a spot on the crater rim in the same place in each image, and that is a control point. We do that for lots of features in each image, and then try to find those same features in other images. As you can imagine, we quickly run up a lot of points, and having a computer program to help us select and track all of these points is important.

Once we have a rich control network made up of points from all of the images we can measure, we can use a computer to perform something called a “bundle adjustment solution.” This action takes those points, and some information from the spacecraft about approximately where it was and where it was pointing when it took each image, and creates a “solution” for each image that correctly places it. This allows us to create mosaics and maps from the images. That is the key to knowing that image A is next to image B, for example, or that image C is higher resolution than either of them and is located within image A.

Pluto
The green crosses in these LORRI images of Pluto’s moon Charon show where we have identified control points between these and other images. Credit: NASA/JHUAPL/SwRI

This kind of map allows us to not only make sense of all the images, it also allows us to combine data from the black-and-white camera and the color cameras, as well as other instruments. It helps all of the scientists on the team put their data together and tell a complete story about these amazing worlds that we have now explored!

Ross Beyer
Ross Beyer

Pluto’s ‘Snakeskin’ Terrain: Cradle of the Solar System?

Today’s blog post is from Orkan Umurhan, a mathematical physicist currently working as a senior post-doc at NASA Ames Research Center. He has been on the New Horizons Science Team for over two years. He specializes in astrophysical and geophysical fluid dynamics, and now works on a variety of geophysical problems, including landform evolution modeling as applied to the icy bodies of the solar system. He is a co-author of a graduate-level textbook on fluid dynamics coming out late this spring.

Greetings and salutations. In this week’s New Horizons blog entry, I want to share with you the exciting possibility that some of Pluto’s surface features may record conditions from the protosolar nebula from which the solar system formed.

A case in point is the image below. It’s what geologists call ‘bladed’ terrain in a region known as Tartarus Dorsa, located in the rough highlands on the eastern side of Tombaugh Regio. (Note that all names used here are informal.) A moment’s study reveals surface features that appear to be texturally ‘snakeskin’-like, owing to their north-south oriented scaly raised relief. A digital elevation model created by the New Horizons’ geology shows that these bladed structures have typical relief of about 550 yards (500 meters). Their relative spacing of about 3-5 kilometers makes them some of the steepest features seen on Pluto.

The Bladed Terrain of Tartarus Dorsa
The Bladed Terrain of Tartarus Dorsa. Credits: NASA/JHUAPL/SwRI

Now, here comes the puzzle. Spectroscopic measurements of this region made by New Horizons’ Linear Etalon Imaging Spectral Array (LEISA) instrument show that this region of Pluto’s surface has a predominance of methane (CH4)—with a smattering of water as well. Naturally, one then would ask, “Can pure methane ice support such steep structures under Pluto’s gravity and surface temperature conditions over geologic time?”

The answer is a meek “maybe.” To date, there are only two known published studies examining the rheological properties (i.e., how much a material deforms when stresses are applied to it) of methane ice in the extreme temperature range of Pluto—a bitterly cold -300 to -400 degrees Fahrenheit. According to one study, the answer is a definite ‘no,’ because methane ice of those dimensions would flatten out in a matter of decades. Yet in another study, methane ice may maintain such a steepened structure if the individual CH4 ice grains constituting the collective ice are large enough. Which study is right? Or is there a way to reconcile them? This is something we simply do not know at the moment.

So before we try to explain how the bladed shapes came to be, we have to make sure we have developed a detailed and controlled laboratory understanding of the behavior of both pure methane ice and methane-hydrate ice. If there were ever an example of why we need further laboratory work, this is it!

But what if it turns out that pure methane ice is always too ‘mushy’ to support such observed structures? Because water is also observed in this region, perhaps the material making up the bladed terrain is a methane clathrate. A clathrate is a structure in which a primary molecular species (say water, or H2O) forms a crystalline ‘cage’ to contain a guest molecule (methane or CH4, for example.). Methane clathrates exist on the Earth, namely at the bottoms of the deep oceans where it is sufficiently cold to maintain clathrate ice. Under those terrestrial conditions, however, methane clathrates are relatively unstable to increases in temperature, causing their cages to open and release their guest methane molecules. This poses a real problem for terrestrial climate stability, since methane is a potent greenhouse gas.

However, under the cold conditions typical of the surface of Pluto, methane clathrates are very stable and extremely strong, so they might easily mechanically support the observed bladed structures. While there is no direct and unambiguous evidence of methane clathrates on the surface of Pluto, it’s certainly a plausible candidate, and we are actively considering that possibility too.

If the Tartarus Dorsa bladed region is comprised of methane clathrates, then the next question would be, “how were the clathrates placed there and where did they come from?” Recent detailed studies (see Mousis et al., 2015) strongly suggest that methane clathrates in the icy moons of the outer solar system and also in the Kuiper Belt were formed way back before the solar system formed – i.e., within the protosolar nebula – potentially making them probably some of the oldest materials in our solar system.

Might the material comprising the bladed terrain of Tartarus Dorsa be a record of a time before the solar system ever was? That would be something!

Orkan Umurhan
Orkan Umurhan
Credits: NASA/ARC/Carrie Chavez