Video: New Horizons animation

Thirteen years outbound from Earth and a billion miles past Pluto, NASA’s New Horizons probe is healthy and on course for a historic New Year’s Day flyby of its next target, a frozen remnant left over from the birth of the solar system 4.6 billion years ago, project scientists say.

Images from NASA’s New Horizons probe show Pluto is a surprisingly active world in the deep freeze of the outer solar system, with jagged 11,000-foot-high mountains of frozen water dusted with a veneer of nitrogen, methane and carbon monoxide ice amid smooth plains and jumbled terrain.

As NASA’s New Horizons probe closes in on Pluto, the Hubble Space telescope has been scouting its retinue of five known moons, discovering that at least two are tumbling chaotically in the complex gravity of the dwarf planet and its large moon, Charon, researchers said Wednesday.