New Horizons Explores Pluto and Its Moons

Pluto and its moons hold many secrets that New Horizons discovered through Alice – its sensitive ultraviolet imaging spectrometer.

Instruments have detected an atmospheric haze which could contain methane. Pluto Underground team has created a unique spacecraft designed to investigate this mystery.

The Mission

As New Horizons will pass Pluto this Wednesday, astronomers will finally have their chance to study it closely up close for themselves. Yet getting this mission off the ground required decades of effort. Following Voyager probes’ success, planetary scientists wanted to send another mission in order to examine Pluto’s five moons as well as Kuiper belt (a distant region beyond Neptune containing icy bodies).

In 1993, JPL scientist Weiler submitted what he called his Astronomical Options (AO) proposal to NASA administrator John Goldin. However, Goldin refused the proposal due to already planning a Europa mission that involved greater technology challenges and had longer timelines for completion.

Krimigis and Stern battled back, winning some battles but losing many more as time progressed. With science budgets constantly decreasing, year-to-year planning of programs was often impossible to implement effectively. After years of effort from Stern’s team led by him alone, in 1997 the National Academies’ decadal survey finally put Pluto-Kuiper belt missions near the top of its medium-sized missions list.

The Spacecraft

However, it was no easy feat launching the legendary Pluto mission. Due to budget cuts and failed proposals over time, its launch became delayed.

Stern persisted, and in 1989 it was discovered that Pluto has an orbiting satellite called Charon that greatly increases its significance and makes sending spacecraft there more attractive.

New Horizons will become the first probe to visit Pluto, an astonishingly varied world with mountains, ice caps and volcanoes. Furthermore, New Horizons will become the first spacecraft to investigate Pluto’s sister moons–including one suspected to contain an underground sea beneath its icy surface.

New Horizons will collect images and science data during its flyby of Pluto in July 2015 with multiple instruments. These include LORRI which will capture topographical maps of Pluto and its five moons; as well as Solar Wind Around Pluto (SWAP) instrument which measures interactions between Pluto and solar wind; comprising fast charged particles created by fast moving sun spots – created and assembled at Johns Hopkins University Applied Physics Laboratory (APL).

The Atmosphere

New Horizons provided breathtaking images of Pluto’s alien landscape, featuring ice dunes and mountains. Astronomers discovered an ongoing haze that cools its atmosphere; now five studies published in Science provide more details about Pluto’s unique, frozen atmosphere.

Studies using ground-based spectroscopy and stellar occultation observations to monitor Pluto’s atmosphere over decadal timescales reveal that nitrogen ice reservoirs, carbon dioxide, and methane all retain heat – similar to how beach sand seems warmer at noon than earlier hours when sunlight levels are highest.

Studies show that Pluto’s haze particles are powered by solar wind, which carries away electrons from neutral atoms to form “pickup ions.” SOFIA’s PEPSSI instrument observed these “pickup” ions streaming away from Pluto as “pickup” ions; SOFIA used that information to calculate particle speed and track how fast they left Pluto’s atmosphere.

The Surface

Scientists have finally seen Pluto in detail after more than six decades thanks to New Horizons’ photographs and maps taken by New Horizons, which provide topographical maps that allow scientists to examine its ice caps, volcanoes and basins.

Pluto’s ice crust displays evidence of recent geological activity. Fissures likely formed as water expanded under its surface and forced cracks and movement through it.

Astronomers also spotted giant mountains composed of nitrogen and methane ice. These mountains can be found in an area named Tombaugh Regio after Clyde Tombaugh, the principal investigator for the mission.

These mountains and other features indicate that Pluto is a young world with an active surface. Over its long orbit around the Sun, its surface experiences many solar interactions involving gas mingling with its surface before flowing deeper into its frozen atmosphere. At perihelion when Pluto is nearest the Sun, solar winds hit and transport gases even deeper into its interior.