In just a few weeks NASA's New Horizons will begin turning what has been up to now little more than a tiny dot of light into a living, vibrant world equipped with multiple, whirling moons. It will visit Pluto, a profoundly
alien place, distant, dark, exceedingly cold, unlike any we have explored to date. To call the spacecraft the
Nina or
Magellan of our planetary journeys is no exaggeration—judged by sheer time and space, this is the most ambitious voyage we have ever undertaken as a species. It has taken almost 10 long years, blazing away across the solar system at more than 10 miles a second, with an extra fling past mighty Jupiter, to bridge the stupendous distance from the inner system to the closest edge of the Kuiper Belt, where Pluto and its icy moons reside. For those of us in our middle years or beyond, this is about as far as any spacecraft will ever actively explore in our entire lives.
We profiled the mission just prior to the halfway point, back in 2009. Now, here we are, finally, and the team is more excited than a kid on Christmas Eve and they're not the only ones! Join me below, as we examine the mission and recognize a dedicated, brilliant team of men and women who have devoted their professional lives to enriching our own.
The New Horizons spacecraft was launched on Jan. 19, 2006, from Kennedy Space Center by a Lockheed Martin Atlas V 551 rocket, equipped with five side boosters on the main stage, and an added third stage to boost to solar escape velocity, meaning the probe will eventually leave the solar system forever. It was moving so fast that it crossed the orbit of the moon within nine hours and hurled past Jupiter about a year later.
The spacecraft has been described as having the size and approximate shape of a baby grand piano. It carries three separate imaging instruments to provide high-resolution pics and wavelength data for weeks before and after encounter: the Long Range Reconnaissance Imager (LORRI) is a highly sensitive, silicon-carbide telescope married to a marvelous camera. It will likely provide the most distinctive overall images for public consumption. There are two other specialized camera-sensors: Ralph, designed for low levels of visible and near infrared light, and Alice, a violet/UV spectrometer to isolate trace constituents in Pluto's wispy, alien atmosphere.
Those instruments and a couple of others have a huge workload ahead of them. Pluto has five known moons, two of which were just confirmed a few years ago. The largest, Charon, is big enough and orbits close enough that it almost makes Pluto a binary planet system. The other four smaller moons are appropriately called Nix, Hydra, Kerberos, and Styx, named after ferocious minions and hellish features deep in the heart of the ancient Roman Greek underworld. There may well be more. This is a complex, whirlagig system shrouded in perpetual night, guarding a rich story for the better part of five billion years.
Fortunately, mission planners designed for more than a weekend at Pluto to learn that story. As New Horizons approaches the system over the next several months, its cameras are able to linger, taking long looks at planet and satellites. As the probe closes, they're able to scale up, to snap faster and faster pics. They have to do this from a platform moving through the system at orbital velocity in ridiculously low light levels, where the sun is a thousand times fainter than it appears from Earth.
Derived from an artist’s impression of how the surface of Pluto might look in plain UN-amplified visible light. The hypothetical image shows ice on the surface, with the large moon Charon in icy crescent to the left, and a spark of a sun to the right barely lighting a thin wisp of atmosphere on the horizon. In reality, we have almost no idea what the surface actually looks like.
Mission planners think that as early as mid-May we may already see better images of Pluto than have ever been taken by Hubble, and they will only get better from there. At closest approach on July 14, New Horizons will skim a mere
7700 miles above Pluto and pass within 18,000 miles of Charon, both at about 10 miles a second, while the entire system is moving transversely in its lazy orbit across the spacecraft's line of approach at another 2 to 3 miles a second. Think of an ultra-high-velocity projectile shot three billion miles and hitting a target moving at mach 10 the size of a parking lot, a feat that would make New Horizons the most accurately aimed "bullet" ever fired.
But that's not the half of it. As it blazes through the system, the spacecraft will have to roll and pan, precisely, on its own, stuck out there so far away that even the speed of light spells a 10-hour round-trip signal lag, to get the sharpest images possible of Pluto and Charon. The landscapes it will capture speeding above and below are, for now, a mystery. We have almost no idea what they will look like in detail. We have to go back to the days of Voyager plying through the moons of Jupiter to fully appreciate how precious this thin window of discovery will be. Once through safely, it will turn around and observe the same valuable real estate for as long as it can, until Pluto and its moons once again recede into starry points and disappear into the diamond-studded, pitch-black cosmic canvas they inhabit.
What happens next is not fully decided. But there is tentative planning for another encounter beyond Pluto in the years to come, with several candidate objects under consideration, all in the 20- to 30-mile diameter range. This is the mysterious realm of the Trans-Neptunian Objects or TNOs, a poorly known nether region of icy bodies spread thinly through a vast volume of space.
These TNO's may all be distant and mostly tiny, but their numbers are legion, and research has shown those numbers were intimately involved in the development of the inner solar system. For the most part, they were cast in ice and rock, near and far from the newly born sun, almost five billion years ago. Millions upon millions were then exiled into distant orbits in wave after wave by the interactions of the newly formed, growing gas giants. About 4.2 billion years ago, it appears Uranus and Neptune were also ejected from their original orbits between Jupiter and Saturn.
The arrival of Neptune and Uranus wreaked havoc on the established orbits of millions of previously exiled smaller bodies, scattering them widely, sending them by swarms into the inner solar system for hundreds of millions of years, many to fiery deaths in glowing craters in a process called Late Heavy Bombardment. This was a dynamic, critical time in planetary history, and it scarred the moon for life and may have nearly split Mars and Mercury wide open.
Despite temporary global destruction, these objects may have delivered critical water and other exotic ices to Earth, and it was right on the heels of that ultra-violent bombardment, about 3.7 billion years ago, when the signs of life first flow so delicately into the geologic record. How and why this happened is the fundamental question in biology, maybe in all of science. The opportunity to examine one or more of those ancient surviving sentinels for any answers is simply too good to pass up. We can do more than hope Congress will fully fund the mission beyond Pluto; we must insist, as the alternative, turning New Horizons off when it's right there, seems unthinkable.
*****
Nothing short of catastrophic collision will stop the probe's ultimate trajectory, because that path is already etched into the sky by 10 years' worth of Newton's best legal work. It may take decades, as the hazy edge of our sunny neighborhood is measured, but soon enough New Horizons will coast beyond the sun's final grasp. The last warm blasts of dying atoms splitting in its power cell will trickle away. The probe will slowly cool to cosmic background as it sails for millennia past the farthest icy sentries of the Oort Cloud, and fade forever into the infinite majesty of deep interstellar space.
Although now silent, its cosmic journey has barely begun. The probe's physical essence, as loyal witness to our own, will ride on for eons to come. It will indeed trek past many stars, but it does not come close to any system in the foreseeable future. If it survives encounters, New Horizons is destined to outlast the pyramids, and it will probably outlast our oceans and mountain ranges. It may even outlast the Earth and the sun. Just imagine how far and wide this bold little spacecraft will have traveled by then.
