PLUTO AND THE NEW HORIZONS MISSION

An analysis of several important discoveries made by the New Horizon’s mission.

DISCOVERY OF PLUTO

Discovered in 1930 by American astronomer Clyde Tombaugh, Pluto was considered by many to be the final planet in our solar system.¹ That changed in 2006 following the reclassification of the term “planet” by the International Astronomical Union.² With the discoveries of Ceres, Haumea, Makemake and Eris, the IAU reconsidered Pluto’s planetary status as Pluto had more similarities and qualities to these objects than to other planets in the solar system. Through the Dawn Mission, scientists were able to observe what are now known as dwarf planets and re-evaluate their classifications as they understood the universe in more depth. In 2015, the New Horizons mission successfully completed it’s mission to Pluto and several important discoveries were made as a result of it’s historic flyby.

PLUTO’S BLUE HORIZON

Pluto’s atmosphere is mostly made up of nitrogen, with carbon monoxide and methane also present.  The atmosphere was measured over 160 kilometres, larger than astronomers could have predicted ¹⁰. During New Horizons fly by of Pluto, it was noted that the atmospheric haze of the dwarf planet presented a bluish haze, when the dwarf planet is in front of the Sun.  Although there is material within the atmosphere which give off a reddish tint, the atmosphere appears blue due to sunlight scattering from haze particles ¹¹.  This red tinted material, called tholins, eventually falls back to Pluto, which is why New Horizons saw a reddish tint closest to Pluto’s surface.  With the photographic information New Horizons was able to capture, scientists saw white patches among the blue haze.  They found the patches to be where the sun reflected off Pluto’s surface, with the largest white patch being Cthulhu Region ¹².  Investigators with the New Horizons missions stated how glorious the sight of a blue sky within the Kuiper Belt was ¹³.

CHARON

Charon being the largest satellite in relative to its planet is half the diameter of Pluto at 1,214. kilometers made up of rock and ice.¹⁴ Charon is filled with mountains and canyons stretching over kilometers across its surface. Its largest Canyon stretches more than 1,699 kilometers which is four times as long as the Grand Canyon. These observations were possible through as NASA’s New Horizons spacecraft passed by Charon on July 14th, 2015 ¹⁴ . Through this mission they were able to observe Charon’s red polar cap. The polar cap is caused by complex compounds called tholins ²¹. Tholins are a result of energetic radiation processing of hydrocarbons through Charon’s extreme temperatures in its atmosphere as gasses from Pluto escape and are trapped by Charon’s gravity ¹⁵.

Through the discovery of the red polar cap and the mass terrain on Charon it has been discovered that Pluto has the largest known glacier in the solar system ranging over 1,000 kilometers wide heart shaped glacier being named Sputnik Planum ²⁰
The surface of Pluto is mostly nitrogen ices and some carbon monoxide ¹⁶. It has been estimated that the surface crust is 250km of ice ¹⁶. Sputnik Planum (SP) is a renowned as the largest known glacier in the solar system. An ironic discovery for the Milky Way’s once smallest planet. This massive glacier is estimated to be 4km thick and 20 degree radius. SP is a probable impact basin located near the anti-Charon point, meaning that it is on the direct opposite side of the planet that Charon remains ¹⁶.

Sputnik Planum is a unique discovery because of its location. The location resulted in the a true polar wander (TPW) for Pluto ¹⁶. A TPW is when a solid-body rotation of a planet on which the location of the north and south poles change, or “wander” ¹⁷. The movement is caused by the plant correcting itself so that the largest moment of inertia is in line with the spin axis ¹⁷. Although planets may appear ‘round’, they often have different moments of inertia because they are not perfectly symmetric. The Earth, for example, has three different moments of inertia ¹⁷.

Sputnik Planum is an anomaly; The probability of an anomaly occurring that close to a tidal axis is about 10% ¹⁶. The low probability adds to the the unique characteristics of Pluto’s structure. “The ability of any mass to reorient a body is counteracted by the plant’s elastic lithosphere, which may preserve an earlier rotational or tidal bulge”. The significance of the geographic presence of SP is that, at present, no bulge has been detected on Pluto.

THE KUIPER BELT

The Kuiper Belt is a disc-shaped region that extends beyond Neptune and is approximately 30 to 55 astronomical units (AU). The region was named so after Gerard Kuiper who, in 1951, proposed that a belt of icy bodies existed beyond Neptune’s orbit to solve the mystery of why we see comets. In 1992, Dave Jewitt and Jane Luu discovered strange objects beyond Neptune, which astronomers call Kuiper Belt Objects (KBOs). While the Kuiper Belt is largely made up of icy bodies and comets, the most famous feature that exists in the Kuiper Belt is the dwarf planet known as Pluto. Objects within the belt are said to be remnants from when the solar system formed around 4.6 billion years ago.

In 2004, astronomers discovered a planet-like trans-Neptunian object that was orbiting the Sun at an extreme distance of about 76 to 1,000 AU from the Sun. The object, who later was named Sedna, takes 10,500 years to orbit the Sun. A year later, in 2005, a KBO was discovered to be about 10% larger than Pluto. This object was eventually named Eris, who takes 560 years to orbit the Sun at about 38 to 98 AU, while Pluto travels around 29 to 49 AU. Eris has a small moon named Dysnomia that is slightly smaller than Pluto. Eris’s discovery forced astronomers to decided whether Eris should be classified as a tenth planet. Thus, in 2006, the IAU created the new qualifications for planet status and dwarf planet class. The recent exploration into the Kuiper belt by Nasa’s New Horizons spacecraft has flew past Pluto in 2015, being the first up-close encounter with a KBO. New Horizons continues to travel deeper into the Kuiper Belt, and is slated to flyby “2014 MU69” January 1, 2019. ¹⁹

CONCLUSION

The construction, launch and data retrieval from the New Horizons satellite was a tremendous success for NASA, producing mountains of new data. Several important discoveries were made, including advanced information about the atmosphere of Pluto and the geology of it’s moon Charon. The New Horizon’s satellite will continue to operate and relay data, it’s next target a Kuiper Belt Object named “2014 MU69”.