As the New Horizons spacecraft closes in on the icy dwarf planet Pluto and its system of moons, astronomers are learning more than ever about this distant family of bodies.

One of the latest discoveries is confirmation that Pluto possesses a thin layer of frozen methane on its surface. Astronomers first detected signs of methane on Pluto back in 1976, but the material has now been seen by an infrared spectrometer onboard the craft.

Methane is colorless and odorless, and is commonly found on Earth in the atmosphere, as well as underground. Astronomers believe methane on Pluto may be left over from the original material that formed the Solar System 4.5 billion years ago.

Pluto is known to be accompanied by at least five moons, and mission planners hope to find more as the spacecraft draws closer to the family of astronomical bodies. Dark and light regions are starting to be seen in more detail as the spacecraft draws nearer, and a dark polar cap has been spotted on Charon, the largest moon of Pluto.

"The science team is just ecstatic with what we see on Pluto's close approach hemisphere. Every terrain type we see on the planet, including both the brightest and darkest surface areas, are represented there; it's a wonderland! And about Charon — wow — I don't think anyone expected Charon to reveal a mystery like dark terrains at its pole. Who ordered that?" Alan Stern of the Southwest Research Institute said.

New Horizons, launched from Earth to Pluto in 2007, will make its closest approach to that body on July 14, 2015. Program managers announced that New Horizons will be passing over the more geologically-interesting hemisphere of the dwarf planet during this closest approach.

Following this close encounter, the piano-sized spacecraft will look back at Pluto, examining sunlight passing through the thin atmosphere of the dwarf planet. This will allow astronomers to study the composition of the material surrounding the distant, frozen body.

"New Horizons is now less than 11 million miles (18 million kilometers) from the Pluto system. The spacecraft is healthy and all systems are operating normally," NASA officials reported on June 30.

On June 30, New Horizons was located roughly 2.9 billion miles away from our home planet. After its encounter with Pluto, the vehicle will continue its journey away from the sun. Mission planners could send the spacecraft to examine a member of the distant Kuiper Belt, a collection of objects orbiting the sun well beyond the orbit of Pluto.