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

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

The Polygons of Pluto

Pluto’s Al-Idrisi Montes
Close up of Pluto’s Al-Idrisi Montes—an example of chaotic polygon-shaped terrain as captured by NASA’s New Horizons spacecraft on July 14, 2015. Credits: NASA/JHUAPL/SwRI

Today’s blog is from Katie Knight, an undergraduate student at Carson-Newman University in Jefferson City, Tennessee. She works with the New Horizons team to help map some of the unusual terrain on Pluto, seeking patterns and estimating sizes and shapes of some of its unusual features.

Hello! My name is Katie Knight, and I’m here to talk about Pluto’s unusual geological features known as polygonal blocks. If you look to the upper left of Pluto’s “heart,” informally-named Sputnik Planum, you will see some chaotic terrain that is very different than the almost smooth terrain of the icy plains. These are the Al-Idrisi Montes, and they are filled with blocks measuring miles to tens of miles across.

Pluto's Sputnik Planum
Sputnik Planum is the bright, western half of the heart shaped region near the middle of this enhanced view of Pluto. The Al-Idrisi mountains are adjacent to Sputnik’s northwestern edge. Credits: NASA/JHUAPL/SwRI

The blocks within even a very small region can be very different. Some are really distinct and appear to be taller – without any other blocks touching them – while others get a bit more complicated. It’s my job to try to separate out which is which.

For example, I analyze them to try to see if these blocks might actually be one big block with some variation in height or if they are separate blocks themselves. The high resolution photos New Horizons took detail the surface with amazing clarity, but they can only show so much.

To look at the size and shape of the blocks, I trace them. The goal is to trace around the base of the blocks, including all the visible sides. Since the blocks cast shadows, some sides are very difficult to see. I am looking to see if there is an area range that is most common or potentially if there is a common shape. It can get complicated, since some blocks seem to blend together. The shadows that the sun casts on the blocks further complicates this analysis, but a lot can be distinguished. The blocks significantly vary in size and shape, but there may be some similarities between them that can be determined.

Pluto’s Al-Idrisi Montes
Close up of Pluto’s Al-Idrisi Montes-and example of how blocks are traced. Credits: NASA/JHUAPL/SwRI

After this first look at size and shape, there are a lot of things we can also analyze. Topography can tell us about the height of blocks and indicate if they not only have some similar area but also a similar height. I am using gray-scale images from New Horizons to analyze the basics of the blocks, though the color pictures can tell us even more about the surface, so later I will analyze those too.

Learning the basics of these blocks will contribute to our knowledge about how the ice blocks formed. There are several theories and studying blocks on another planet will tell us even more. Chaos terrains like these on Pluto, while very different, can be compared to chaos on Mars and Europa to see what is common between all three of these and what that can tell us about the surface of all of these bodies.

The area I am looking at may be relatively small, but there is a lot we can learn from these blocks and I can’t wait to see more of what Pluto has to offer!

Katie Knight
Katie Knight

Where’s My Data? Keeping Track of New Horizons’ Treasure of Information

Pluto
Last summer’s historic flyby of Pluto and its moons generated a wealth of science data, capturing this new world which had never before been explored. Thousands of high resolution images, spectra and particle data were recorded on the spacecraft’s two solid state recorders as the spacecraft flew by its targets. It was a fast flyby, with the spacecraft traveling at 9 miles (14 kilometers) per second. To maximize the amount of time gathering data, very limited time was spent with an Earth-pointed spacecraft during the encounter itself, and thus only a select few images were transmitted back to Earth during the flyby. The rest of the data remained on the spacecraft waiting for the commands to be executed that would compress, packetize and transmit the bits to the ground.

My name is Emma Birath and I work on the Science Operations team at Southwest Research Institute in Boulder, Colorado. We operate the science instruments onboard the spacecraft; for the encounter it was our job to build observations that accomplished the scientists’ objectives, while also satisfying spacecraft and navigation constraints. In addition to commanding the science instruments, it is also our responsibility to write the command sequences for the compression of the science data, and the transmission of the compressed science data to NASA’s Deep Space Network of radio receivers on Earth.

Due to very low downlink rates with a spacecraft that is 3 billion miles away (and counting), it will take more than a year to get every bit down from the Pluto encounter sequence. Today – about 7 months after the encounter – more than half of the data is still on the spacecraft! Because of the long duration downlink period, it is important that this work is done as efficiently as possible.

data screen
New Horizons DataTrack Interface

To facilitate the playback of New Horizons’ encounter data, I led an effort to build a piece of software, called DataTrack. DataTrack consists of a web-based user interface, with a MySQL database backend. It allows us to schedule and sequence playbacks for each command load sent to the spacecraft. It helps us keep track of all data sets from the encounter load, and at what stage they are in the downlink process. It also helps us track the processes of mathematical data compression on New Horizons, which is necessary to maximize how much data we can get back to the ground each week and month. Has a data set been compressed already? What compression type was used? What is the estimated data volume, and will it fit in an upcoming downlink track? It flags errors that may be introduced in a playback sequence, and ensures efficiency and optimization.

Flying a spacecraft is risky, and at any time something could happen in which we lose contact and any information that hasn’t already made it to the ground, so the prioritization of the data sets by the science team is critical. DataTrack allows us to keep track of what’s been sent to the ground, what’s scheduled to be sent, and what’s left to plan for; it also lets us track what data has been compressed.

Another important purpose of the software is to provide the science team with information on when a particular data set is expected to reach the ground. It has greatly improved communication across team boundaries.

Working on this team has been an incredible, once-in-a-lifetime experience. Seeing years of hard work and patience come to fruition has been exhilarating and very rewarding. I have to pinch myself from time to time, reminding myself how lucky I am to work in this field and to be part of the exploration of the solar system!

Emma Birath
Emma Birath / Credit: Michael Soluri

 

The Many Faces of Pluto and Charon

Today’s blog post is from Kimberly Ennico, a member of the New Horizons’ Composition Theme Team and one of the deputy project scientists. She works at NASA’s Ames Research Center in Moffett Field, California, and has been on detail to the Southwest Research Institute in Boulder, Colorado.

No one can doubt the beauty of Pluto and Charon—amazing worlds revealed by the images from NASA’s New Horizons mission. From Pluto’s mountains, glaciers, ice-volcanoes, blue skies, and layered colorings to Charon’s vast tectonic structures and enigmatic red-colored pole, these pictures and associated spectra are rich puzzles waiting to be solved.

The July 14, 2015 Pluto flyby gave us an initial look at one side of Pluto, with its iconic heart-shaped feature. But I’m interested in the full planetary perspective, finding the “other sides” of Pluto to be every bit as fascinating as the encounter hemisphere. We must remember that a flyby is a moment in time lasting a few hours. In contrast, Pluto and Charon each rotate about its axis every 6.4 Earth days. This means that when New Horizons flew through the Pluto system it captured one hemisphere of each body in incredible detail.

What do we know about the “other sides” of Pluto and its largest moon? In the three weeks before the flyby, the Long Range Reconnaissance Imager (LORRI) and Multispectral Visible Imaging Camera (MVIC) imaged Pluto and Charon every day, sometimes two or three times a day to gather as much coverage across the bodies as New Horizons closed in. LORRI is New Horizons’ primary camera, an 8-inch telescope outfitted with an unfiltered charge-coupled device (CCD) – like you’d find in your own digital camera – sensitive to visible light. MVIC is a separate instrument with multiple CCDs, for which several are outfitted with color filters. The highest resolution images of the “other sides” of Pluto and Charon were observed 3.2 Earth days earlier, around July 10-11.

Working with a subset of the data (as not all these images have been sent to Earth from New Horizons yet), we’ve received our first glimpse of these “non-encounter” hemispheres below.

Four Faces of Pluto
Four faces of Pluto in black-and-white and color. From left to right, the central sub-observer longitudes are ~180, 240, 360 and 60 degrees East Longitude. The Pluto “Encounter Hemisphere” (indicated by the white box) is most recognizable by the “heart” feature of the informally-named Tombaugh Regio. This is also the hemisphere that today never faces Charon, as Charon is “tidally locked” to Pluto, similarly to how the Earth only sees one face of our moon. Pluto’s “Charon-facing” side is the second column from the right. Pluto’s north pole is up in all these images. The top row contains LORRI grey-scale images taken on July 13, July 12, June 27 and July 3rd, when Pluto was 620, 189, 24 and 36 LORRI pixels across, respectively. The bottom row shows MVIC “enhanced-color” images made by combining the near infrared, red and blue filters. They were taken on July 13, July 12, July 10 and July 9, when Pluto was 163, 56, 26 and 21 MVIC color pixels across, respectively. All these images surpass what we had previously seen from Hubble Space Telescope imagery where Pluto’s disk was only about 12 pixels across. Of course, New Horizons was only millions of miles from Pluto—Hubble is over 3 billion miles away! Credits: NASA/JHUAPL/SwRI
Six faces of Charon
Six faces of Charon. Central sub-observer longitudes: top, from left to right, 350 (B&W), 2 (color), 32 (color); Bottom, from left to right, 67 (color), 86 (B&W), and 180 (color) degrees East Longitude. The side that faces Pluto is highlighted by the inset box. From left to right, the top row images were taken July 14, 14 and 13, 2015, with Charon spanning 523 (LORRI), 81 (MVIC), and 43 (MVIC) pixels. The bottom row images were captured from July 12, 12 and 10, 2015, with Charon spanning 28 (MVIC), 96 (LORRI), and 13 (MVIC) pixels. Charon remains a mainly neutral greyish color all around, with a distinct red northern polar cap appearing from all sides. Credits: NASA/JHUAPL/SwRI

What strikes me most about the new Pluto color images is that the latitudinal (horizontal) banding identified on the encounter hemisphere is evident all around Pluto. Specifically, the northern polar region has a distinctive color from adjacent latitudes. The darkest region, which spans the equator, also appears to continue around Pluto, showing distinct variations on the side facing Charon, which have yet to be understood.

Why is this interesting? Coloring on Pluto is thought to have been the result of hydrocarbons called tholins that have formed in the atmosphere and have been “raining” down on Pluto’s surface over the millennia. We’re investigating whether Pluto’s colored terrains are primarily due to changes in or movements of its surface ices, specifically whether they have been undergoing seasonal effects –changing in temperature over time from the amount of cumulative sunlight – which could display itself as horizontal banding. The presence of that vast reservoir of methane, nitrogen and carbon monoxide ices in Pluto’s “heart” complicates the picture and could serve as a visible marker to trace changes.

Over the next few months, as more of this late-approach imagery gets downlinked from the spacecraft’s recorders, we will continue to piece together this colorful story of Pluto and Charon – from all sides.

Kimberly Ennico
Kimberly Ennico and Pluto, Clark Planetarium, Salt Lake City, Utah

Pluto: Ultraviolet Amazement

Eric Schindhelm is a research scientist at the Southwest Research Institute in Boulder, Colorado. He supported the Pluto system encounter in summer 2015 as part of the Atmospheres team for New Horizons.

I was very fortunate to participate in the New Horizons Pluto encounter last summer, supporting the Atmospheres science theme team.

I arrived at the Johns Hopkins Applied Physics Laboratory in Laurel, Maryland—home of New Horizons mission operations—a few weeks before the historic July 14 Pluto flyby. My job was to prepare to analyze data from the Alice instrument, a sensitive ultraviolet imaging spectrometer designed to probe the composition and structure of Pluto’s atmosphere. While a spectrometer separates light into its constituent wavelengths (like a prism), an “imaging spectrometer” like Alice separates the different wavelengths of light and produces an image of the target at each wavelength – so we were really looking forward to some incredible and valuable data.

Over the following weeks, as we approached the Pluto system, the Ralph and Long Range Reconnaissance Imager (LORRI) instruments returned increasingly amazing images and spectra. From the cracked and cratered surface of Pluto’s largest moon, Charon, to clear compositional differences across Pluto itself, these icy worlds at the edge of our solar system were turning out to be even more interesting than we expected. To be honest, I was starting to get a little jealous of the results pouring in from LORRI and Ralph. When would we get to see Pluto appear in Alice data?

The challenge was that at far-ultraviolet wavelengths (550 to 1,850 Angstroms), Pluto and Charon are only visible in reflected sunlight, and the sun is particularly faint at those wavelengths. By contrast, the sun is much brighter at the visible and infrared wavelengths that LORRI and Ralph use. We made some calculations about when we should get our first glimpse of Pluto in Alice data and the result turned out to be on Sunday July 12, just two days before closest approach!

When that Sunday evening came I kept checking the server to see if the data had reached the ground and gone through the data-reduction pipeline. Before too long I saw the data and downloaded it to my computer with anticipation. I used an adjacent row on the detector to determine the background to subtract, producing the plot below with an obvious surplus of photons at higher wavelengths.

First detection of Pluto with the Alice UV spectrometer. Credits: SwRI/Eric Schindhelm
First detection of Pluto with the Alice UV spectrometer. Credits: SwRI/Eric Schindhelm

The variation of counts from 1,300 to 1,500 Angstroms gives you an idea of how ‘noisy’ the data was at the time, but longward of 1,500 Angstroms there was clearly a signal from Pluto. Pluto’s ultraviolet signal was rising out of the noise! While spectra are not as immediately aesthetic as images, there was a certain beauty to these data – these were the first far-ultraviolet photons from Pluto ever to be detected by humans. This cannot be done from Earth with the tools anyone has available – the signals are too faint. You have to send a spacecraft to Pluto to get data like this, which are useful for determining the composition of Pluto’s surface and atmosphere. And that requires quite a bit of teamwork to design, build, and launch a spacecraft to fly all the way to the outer solar system. When I saw this on my computer, I knew that the New Horizons team had succeeded and recorded the first far ultraviolet spectra of Pluto!

A few minutes later, a large group came back from dinner, and among them was Annette Tombaugh Sitze, daughter of Clyde Tombaugh – the man who discovered Pluto in 1930. They were at our hotel (where I was working) to socialize, but I just had to show off New Horizons’ latest find. Annette was excited to see her father’s planet in the far ultraviolet for the first time, and related how he used to teach her about astronomy when she was a child. At the time, my wife was pregnant with our first child, and I was struck by a great sense of continuity in the human experience of exploration and understanding. It was fascinating to see the New Horizons spacecraft turn the Pluto system from a few points of light into a complex and dynamic system of worlds. I’m grateful to have been a part of that and can’t wait to tell my new son about it when he grows up.

Before I go, I want to mention that –in addition to the New Horizons data –we were awarded time on the Hubble Space Telescope to look at the same side of Pluto and Charon that New Horizons viewed as it flew past, using the Space Telescope Imaging Spectrograph to obtain mid-ultraviolet spectra from 1,850 to 3,200 Angstroms. The sun is much brighter here than at the far-ultraviolet wavelengths, so Hubble is capable of seeing Pluto in this wavelength range all the way from Earth — 3 billion miles away. The Hubble data bridge a gap of spectral coverage between what Alice and Ralph cover, allowing us to check close-up spectra obtained by New Horizons against those observed at Earth. The spectral signatures due to Pluto and Charon’s surfaces should be consistent across all wavelengths. Stay tuned for those results!

Eric Schindhelm
Eric Schindhelm with the Alice imaging spectrometer. Credits: NASA/Kim Ennico-Smith