The New Horizons spacecraft is closing in on Pluto. It will rendezvous with the dwarf planet one year from now on July 15, 2015. Since its launch in 2006, the spacecraft has been speeding through interplanetary space at nearly a million miles per day. New Horizons, the first probe to travel to Pluto, is now only about 280 million miles from its historic close approach with the planet and its moons.
New Horizons will try to help scientists understand where Pluto and its largest moon, Charo,n "fit in" with the other objects in the solar system. We classify the solar system into zones. Earth, Mars, Venus and Mercury are the rocky "terrestrial" planets. In contrast, thick, molecular hydrogen atmospheres dominate the “gas giant” planets, which include Jupiter, Saturn, Uranus and Neptune. Pluto is the second largest body in the Kuiper Belt, the icy "third zone" of our solar system.
The Kuiper Belt is a vast reservoir of icy objects just outside of Neptune's orbit and extending out to about 5 billion miles from the sun. This region is thought to be the source of most short-period comets, those with orbits shorter than 200 years. These bodies have solid surfaces, but, unlike the terrestrial planets, a significant portion of their mass is icy material such as frozen water, carbon dioxide, molecular nitrogen, methane and carbon monoxide.
No spacecraft has ever explored Pluto and Charon, so this visit to the new frontier of our solar system promises to tell scientists about the surface properties, geology, interior makeup and atmospheres on these bodies and about the origins of our solar system.
The Hubble Space Telescope recently concluded a preliminary search of Kuiper Belt objects the spacecraft can visit after its flyby with Pluto. A more intensive search of these outer solar system objects with Hubble is planned by mission managers.