Pluto’s New Horizons

by: Chris Thompson

With the arrival of the New Horizons space probe at Pluto, a ten year old space-fanatic gets a chance to finally realize his dreams….

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I‘ve been waking up every morning this week feeling like I was ten years old again. Back then, I’d lay awake in bed in the early morning silence before my mother roused me for school and stare up at the colorful National Geographic map of the solar system my father had given me to tack upon my bedroom wall. I’d imagine myself on heat-scorched Venus, or on the red sands of Mars, or even floating down, down through the thousands of miles of storm-filled clouds that made up the gas giant Jupiter’s atmosphere. It was a time of wonder for me, before the necessities and routines of the day took hold, and in the end, my eyes would always wander across that map to the little known planet, Pluto. I’d linger there on that brown featureless orb, my thoughts struggling to comprehend what it would be like to gaze upon its rocky lands, because of how little I knew then about that dim, distant world.

That was 1987, decades before we would send the New Horizons space probe to Pluto, and yet the United States was already fully established in space exploration, with NASA’s bold plan to survey all of the major bodies in our solar system already in full swing. We had visited Mars years earlier, with the Viking Program’s twin landers, and had done stunning flybys of Jupiter and Saturn and the ice giants with the Voyager and Pioneer probes’ Planetary Grand Tour. So this July 2015, as the days of the week ticked by, and the news and images of Pluto from the New Horizons space probe dribbled in, capturing the attention of the world, I felt like I was once again in my bedroom, staring up at that old map of the planets. Except now, I had words and colors and features I could add to my ten year old self’s vocabulary for Pluto’s lonely realm. Words like Charon and Hydra and Nix. And dark, mysterious names for its newly-discovered features like Mordor and Cthulhu, Balrog and Meng-p’o. Spine-chilling names borne of H.P. Lovecraft and J.R.R. Tolkien and Buddhist and Mayan mythology that would seem more at home in one’s nightmares than a planetary map. I had been waiting decades for these moments to arrive, for a time when I could finally fill in those gaps in my imagination for Pluto. And now that they are here, New Horizons has bridged the three billion mile chasm between my adult self and the ten year old boy who still dwells inside me, eager to learn more about Pluto and its moons.

What we knew about Pluto before New Horizons screamed by the dwarf planet at a blistering 30,000 mph we could fit in a small chapter of a textbook about our solar system. What we know now however, and will continue to learn over the next sixteen months as the remainder of the data is downloaded, will fill its own textbook. One we should call “Pluto: The Dynamic Dwarf Planet of the Underworld.” And what we will have gleaned from New Horizons’ myriad set of instruments as they continue to scan these far-flung, icy worlds, can only serve to influence and change our understanding of planets and their formation for generations to come. It’s a truly wonderful time to be alive and to bear witness to the fact that there are still awe-inspiring discoveries to be made in these modern times.

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If one wants to get an interplanetary spacecraft as far away as Pluto as quickly as possible, while everyone who has a vested interest in the study of the dwarf planet is still alive, the easiest way to do that is to make the probe as small as possible and strap it to a gigantic rocket. In January of 2006 NASA did just that, packing the radioactively-powered, grand piano-sized New Horizons atop a towering Lockheed Martin Atlas V rocket. New Horizons, with its massively powered lift-off and subsequent escape from Earth, has been referred to as the fastest spacecraft ever launched, with the probe attaining a launch speed of well over 36,000 mph! Traveling at that rate, the probe only took nine hours to reach the moon later that day.

On its decade long journey to Pluto, New Horizons fired its rockets several times to pick up additional speed and used a gravitational-slingshot from Jupiter, less than a year after its launch, to further accelerate. Using Jupiter’s relative movement as it tugged downward on the approaching spacecraft, New Horizon was able to pick-up an additional 9,000 mph in speed from the planet, rocketing it further onwards, pushing its velocity up over 50,000 mph and shortening its travel time by three years. During the lead-up to Jupiter’s closest approach, the space probe used the time before its encounter with the planet’s gravity to perform a four-month, intensive study of the Jovian System, turning its state-of-the-art cameras and scientific instruments on the planet and its moons. It returned stunning panoramas of the gas giant, observing its dynamic atmospheric conditions and analyzing the structure and composition of its vibrantly-colored clouds. It spied volcanoes erupting on one of its moons, Io, and detected the signatures of Jupiter’s faint, gossamer rings.

jupiter

After its visit to the Jovian System, New Horizons continued onwards, entering into hibernation mode for the bulk of its remaining journey, passing by the orbit of Saturn in June of 2008 and Neptune in March 2011. Then in July of 2013, New Horizons awoke from its slumber to train its cameras on Pluto, and for the first time was able to resolve the dwarf planet and its primary moon Charon, as separate objects. And then in December of last year, NASA scientists finally sent the signal to awaken New Horizons from its deep sleep and to begin its main Pluto Scientific Operations. Since that moment it has been a wild ride for the New Horizons team, and every byte of data that arrives is one more piece of information that we’ve never had before.

The data trickling in now from New Horizons will take almost a year and a half to be fully downloaded, due to the incredible distances involved (over three billion miles and counting!) and the low rate of power available to the space probe to transmit it to us. New Horizon packs a pair of 12-watt radio transmitters as a way of speaking to NASA and its Deep Space Network, but that’s less power than is needed to light a single lightbulb and that low bit-rate of data, traveling at the speed of light, still takes four hours and twenty-five minutes to cross the great gulf to Earth. But the data is arriving, slowly but surely, and the full-story of the flyby still remains to be seen, but what New Horizons has sent us so far is already telling us that Pluto and its moons are full of awe and wonder.

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New Horizons closest approach to Pluto will have brought it just over 7,800 miles above its surface. During that time, the space probe executed a complicated series of tiny, pre-loaded maneuvers, numbering in the hundreds, that allowed it to capture data on Pluto, its largest moon Charon, and the surrounding system. To their complete surprise, NASA’s New Horizons team of scientists have already learned from those maneuvers that Pluto is geologically active. Even now, its icy surface is being sculpted, but not by outside forces such as tidal heating, wherein the gravitational interactions with a much larger planetary body causes it to warm, but by Pluto’s own internal heat. What that means for our understanding of a planet’s geologic capabilities is epic, for never before have we encountered the possibility that a world could do this and it suggests that some other, unknown process is causing its geologic activity. According to John Spencer of the Southwest Research Institute in Boulder, Colorado, and the deputy lead of New Horizons Geology, Geophysics and Imaging Team, “This may cause us to rethink what powers geological activity on many other icy worlds.” It’s a historic finding, not to be underplayed, for it has the potential to send a lot of geophysicists back to the drawing board to rewrite the book on planetary dynamics. In addition, new close-up images of Pluto’s surface near its equator, have revealed another surprise, giant ranges of mountains, composed of the dwarf-planet’s water-ice “bedrock”1 and towering over 11,000 feet, putting them in league with the western United States Rocky Mountain range. Formed likely no more than 100 million years ago, a relatively youthful age compared to the 4.5 billion year or so age of our solar system, these towering ice mountains are one example of why scientists feel that Pluto may still be geologically active, based primarily on the fact that there are no impact craters surrounding them. One would expect on a planet as old as Pluto, that over billions of years, its surface would be pock-marked and heavily cratered with the telltale signs of impacts, but that is hardly the case.

pluto surface

Pluto’s largest moon, Charon, is fast emerging as its own world as well. Roughly half the size of Pluto, and gravitationally locked to its parent so that the two objects keep the same face towards the other, the moon exhibits relatively few craters, indicating a young surface that has been recently reshaped by geologic activity. Scientists had expected its surface to appear ancient and covered in craters but instead found a varied and fractured terrain. There is a large swath of cliffs and troughs stretching left to right across the moon for upwards of 600 miles that suggest a fractured crust likely due to internal geological processes and to its upper right, there is what appears to be a massive chasm, deeper than Earth’s Grand Canyon, and plunging an inconceivable 4-6 miles into Charon’s icy depths. A vast reddish dark region to the north of the moon, with diffusely defined boundaries suggesting a thin deposit of material that came from Pluto, has been named Mordor, after the fiery region in J.R.R. Tolkien’s fictional universe of Middle Earth occupied and controlled by the great evil Sauron. The space probe has also revealed more about one of Pluto’s numerous smaller moons, Hydra, revealing it to be an elongated object composed mainly of water ice and to be about 27 by 20 miles in size.

There is still more data to come, and lots more science for New Horizons to perform. With each successive data downlink we’ll learn more and more about this icy system orbiting out in the inky blackness, billions of miles away from our sun. We’ll learn about the dwarf planet’s other moons, Kerberos, Styx and Nix. We’ll learn about Pluto’s atmosphere and how it behaves and whether Charon has one too. We’ll learn about all this and more, and as the brave space probe rockets forever onward, moving past the Plutonian System into the outer regions of our solar system, it will find new targets to train its instruments on. As I type this, New Horizons is already racing away from Pluto and its moons at 30,000 mph, peering back at the system and collecting as much data as it can. But what lies ahead is just as fascinating to behold as what it will leave behind, for New Horizons has already taught us how varied and diverse objects flung this far out from the sun can be. And as New Horizons plunges further into the unknown, it’ll become the first space probe to visit the mysterious Kuiper Belt, a ring of icy blocks encircling our solar system and filled with thousands of stalled worlds that are the building blocks of planets our solar system never made. And beyond that, who knows, for New Horizons is unstoppable and could go the way of the Pioneer and Voyager space probes. It could travel on for decades to come, eventually passing beyond the influence of our solar system, and break-out into true, interstellar space. What lies out there one can only guess, but I’m confident the ten year old inside of me will be eagerly awaiting the news.



  1. “At Pluto’s temperatures, water-ice behaves more like rock,” -deputy GGI lead Bill McKinnon of Washington University, St. Louis []

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