Last Friday, December 2, 2011, NASA’s New Horizons spacecraft became the closest spacecraft ever to Pluto, a record previously held by Voyager 1 which came within 983 million miles of Pluto on January 29, 1986. This marks the beginning of a new period in the New Horizons mission, when every day – every moment, in fact – is the closest a manmade vehicle has ever come to the distant dwarf planet!
“What a cool milestone!” said Alan Stern of the Southwest Research Institute and New Horizons Principal Investigator. “Although we’re still a long way – 1.5 billion kilometers from Pluto – we’re now in new territory as the closest any spacecraft has ever gotten to Pluto, and getting closer every day by over a million kilometers.”
Launched on January 19, 2006, New Horizons has been traveling at incredible speeds through the solar system for 2,149 days (as of the time of this writing.) The spacecraft is one of the fastest machines ever created, speeding through interplanetary space at up to 47,000 mph. That’s over twenty times the speed of a rifle bullet – almost 13 miles a second!
Yet, even at that rate, it will take New Horizons another 3 1/2 years to finally reach Pluto, a frozen and enigmatic world holding court with its four (known) moons at the far reaches of the solar system. At its closest Pluto is still over 4.2 billion miles from Earth. From that distance the Sun is just an extra-bright star in an eternally twilit sky, casting about as much heat as the pad of sticky-notes on your desk.
Still, over the course of its 248-year-long orbit that heat is enough to visibly change the coloration of its surface, at least as most recently seen by the Hubble Space Telescope in a series of images acquired from 2002-2003. Likely an effect of surface materials sublimating and re-freezing across Pluto’s surface, these shifting patterns indicate that Pluto is a dynamic place that undoubtedly has many more surprises in store for NASA’s steadily approaching spacecraft.
New Horizons will ultimately make a close pass by Pluto on July 14, 2015, imaging the dwarf planet with a suite of science instruments, in particular its high-resolution LORRI (Long Range Reconnaissance Imager) camera which will be able to resolve features on its surface as small as 200 feet across.
After its close encounter with our solar system’s erstwhile ninth planet New Horizons will continue outwards into the Kuiper Belt, an even further region where icy bodies and even more worlds like Pluto reside, orbiting the Sun in ever larger and longer orbits.
New Horizons may even visit one of these distant worlds, should the mission be extended.
Ultimately, in another few years (1,312 days and counting, to be exact) we will learn more about Pluto in one sudden and glorious burst of information than we ever have in the 81 years since its discovery, thanks to New Horizons. Until then we can only imagine what it might find.
See you in 2015!
Read more about the New Horizons mission on the Johns Hopkins University/APL mission page.