New Horizons for Solar System Exploration: To Pluto and Beyond
To quote the late sci-fi author Douglas Adams, “Space is big, really big. You just wouldn’t believe how hugely, vastly, mindbogglingly big space is. You might think it’s a long way down the road to the chemist but that’s just peanuts to space.” It takes a really long time to traverse the vast distance of even interplanetary space from Earth to Mars. The recently deceased comet ISON spent the better part of a year travelling between Jupiter to the Sun before its demise in the Sun’s inferno. Jupiter is roughly 778,000 kilometers from the Sun and Saturn is nearly twice that far away at 1.4 billion kilometers away. Twice the distance from the Sun to Saturn is Uranus sitting a whopping 2.8 billion kilometers from the Sun. Even further still is icy Neptune, so far away it’s existence was predicted before it was directly observed sits an incredible 4.8 billion kilometers from the Sun. At this point in the solar system the Sun is nothing more than a small point of light almost appearing as just another background star in the Milky Way. But the orbit of Neptune is just the seashore of the cosmic ocean that is our solar system. Far beyond the orbit of Neptune lies a huge area known as the Kuiper Belt which is home to an unknown number of tiny icy worlds. The most well-known of the Kuiper Belt objects (KBO) is the dwarf planet Pluto. Until 2006 Pluto was recognized as the ninth planet in the solar system but was downgraded to dwarf planet when astronomers began discovering objects in its neighborhood that were both larger and smaller. Pluto lies a mindbogglingly 5.8 billion kilometers from the Sun. Together with its large moon Charon, Pluto marks the beginning of unexplored territory in our solar system. No human spacecraft has ever visited Pluto. Much of Pluto’s characteristics are unknown to us. The same goes for all of the KBO’s in Pluto’s neighborhood.
NASA is on the verge of changing that. The New Horizons spacecraft which was launched in January 2006 is just a year away from the beginning of its mission at Pluto. New Horizons is travelling at about 1 million miles per day as it speeds into uncharted waters so to speak. Currently approaching the orbit of Neptune, New Horizons is approximately 4 billion kilometers from the Sun. The probe will arrive at its closest approach of Pluto on July 14, 2015 but the science will begin well before that in January 2015. New Horizons is equipped with many instruments to help scientists analyze Pluto. One such instrument is the Long Range Reconnaissance Imager (LORRI) which is essentially a long focal length telescope with a CCD imager to take high resolution images of the Plutonian surface beginning in January 2015.
An Historic Mission
Pluto is part of a vast unexplored trans-Neptune region of the solar system called the Kuiper Belt. The inhabitants of the Kuiper Belt are thought to be the leftovers of planetary formation when rocky and icy bodies were being flung around the solar system. These icy worlds didn’t quite form into full-fledged planets but they are worlds nonetheless. Only five human spacecraft have ever traveled in this cold void before. New Horizons is the first spacecraft to be sent to directly study a new body since the Voyager probes thirty years ago. For my generation (milllennials) this is akin to the Apollo 11 moon landing in its scientific value. I can’t think of any mission that is more important to the understanding of our solar system than New Horizons.
New Horizons will provide scientists with a smorgasbord of priceless data about Pluto and the KBO’s nearby. Besides LORRI New Horizons is equipped with an ultraviolet spectrometer (ALICE) which will be used to analyze Pluto’s atmosphere, an optical/infrared instrument (RALPH) that will be used to create maps of the surfaces of Pluto and Charon, a particle detection instrument (PEPSSI) used to detect molecules escaping from the atmosphere, a particle instrument (SWAP) to measure the solar wind at Pluto, a radio instrument (REX) to observe the atmosphere and a student created instrument to collect dust particles that have traveled from the inner solar system. The only thing we know about the surface of Pluto is from Hubble which provide a low resolution map that can only resolve surface features that are hundreds of kilometers in size.
One of the more interesting observations New Horizons will make is the study of Pluto’s atmosphere. Pluto’s orbit is highly inclined to the ecliptic, the plane all the planets orbit in, and is highly eccentric (oval shaped). This means that Pluto’s distance from the Sun varies greatly depending on where it is in its orbit. The vast distance change is thought to cause molecules in Pluto’s atmosphere to condensate and sublimate and be lost to space. The ALICE, PEPSSI, and REX instruments on New Horizons will measure the constitution of Pluto’s atmosphere and the rate at which it is being lost to space.
Once New Horizons has completed its mission objectives for Pluto and Charon it will move on to studying some nearby KBO’s if any are in the vicinity. So little is known about the Kuiper Belt and its citizens so any information on these icy worlds is practically invaluable. The mission is slated to end in 2026 but if the spacecraft is still operational NASA has targeted the edge of the solar system just like with the Voyagers 1 and 2 missions. Hopefully New Horizons will be able to reach the heliopause (the region where the solar wind from the Sun begins to interact with interstellar particles) and map this boundary point. With the data from Voyager still inconclusive it is necessary to continue to explore this strange region of space. The spacecraft is predicted to be inoperable by 2038 signally the end of its lifetime. By then New Horizons will have contributed a massive volume of science and radically changed the way we view our solar system’s outer reaches. Who knows what we’ll see when it finally reached Pluto next July? Besides the data New Horizons provides, the probe is fulfilling our human curiosity and our desire to explore. Space is the last frontier and there sure is a lot out there!