New Horizons extended mission approved; Sputnik Planum nitrogen ice shows intricate patterns
NASA has officially given the green light to the mission extension of their New Horizons spacecraft – a visit to the small Kuiper Belt Object (KBO) known as 2014 MU69, located close to a billion miles beyond Pluto. The small KBO was found with the Hubble Space Telescope after ground-based observations failed to find a suitable object for the spacecraft to visit after Pluto.
Four engine burns, conducted between October and November of 2015, placed New Horizons on track to its second target.
Frozen in the Kuiper Belt, MU69 has remained largely unchanged since the formation of the Solar System 4.6 billion years ago. Studying it will provide scientists with insights into the Solar System’s building blocks.
MU69 measures approximately 30 miles (45 kilometers) across, about 10 times larger and 1,000 times more massive than the average comet.
At 0.5 percent the size of Pluto with one-ten-thousandth of Pluto’s mass, MU69 is of an intermediate size for a KBO, significantly larger than a comet yet much too small to be a dwarf planet.
The flyby will occur on January 1, 2019. New Horizons will come four times closer to it than it did at Pluto, just 1,900 miles (3,058 kilometers) from the KBO’s surface.
From that distance, imaging and mapping spectroscopy will be of higher resolution than obtained at Pluto.
All seven of the spacecraft’s science instruments will observe MU69. Studies will focus on its surface composition, surface mapping, the search for an atmosphere, and a search for moons.
The total data collected will take 20 months to return to Earth and is expected by late 2020.
If the extended mission had not been approved by NASA’s 2016 Planetary Mission Senior Review Panel, New Horizons’ instruments would have been turned off after the return of the spacecraft’s Pluto data is completed this autumn.
“The New Horizons mission to Pluto exceeded our expectations, and even today, the data from the spacecraft continue to surprise,” said Jim Green, NASA Planetary Science Division Director. “We’re excited to continue onward into the dark depths of the outer Solar System to a science target that wasn’t even discovered when the spacecraft launched.”
Southwest Research Institute scientist Alex Parker, who works for the New Horizons mission, describes in his June 28 blog entry, “A World Beyond Pluto: Finding a New Target for New Horizons“, the process by which the mission’s second target was found.
Parker recounts the arduous search, which began in 2004, even before the spacecraft launched. He came on board in 2011 and played a key role in writing the software used in the successful 2014 Hubble search, which located five potential KBOs in New Horizons’ path.
MU69 is a “cold classical KBO”, meaning it is a remnant of the proto-planetary disk from which the Solar System formed that has remained virtually unchanged.
New Horizons’ extended mission will also observe approximately 20 other KBOs from a distance, Parker notes.
In a second blog entry dated July 1, titled “From Canada to Pluto and Beyond“, he discusses Canada’s contributions to the mission, including continued tracking of MU69 in anticipation of the 2019 flyby.
Data from the Pluto encounter, now nearly one year ago, continues to be returned, with the most recent showing intricate surface patterns in the nitrogen ice plains of Sputnik Planum, the left side of Pluto’s “heart” feature.
Two photos (shown below) present an enlarged view of the region highlighted in the rectangle on the sphere of Pluto seen at the extreme left. The inset on the left uses enhanced color to emphasize the region of Sputnik Planum in greater detail.
All the data in these images was collected by the Ralph / Multispectral Visible Imaging Camera (MVIC). The left inset has a resolution of about 2,230 feet (680 meters) per pixel. It was taken from a distance of 21,060 miles (33,900 kilometers) only 44 minutes before closest approach.
The enlarged image on the right is a “scattering map” of the polygonal plains composed of two separate pictures of the area taken at different angles. It depicts both bright and dark areas in this sector of Sputnik Planum. The bright areas are those that have smooth textures and, therefore, reflect sunlight forward, in the direction away from the Sun. In contrast, the dark regions have rougher textures and reflect sunlight toward the Sun.
With the combined image, mission scientists can see distinct patterns within the polygonal cells not visible in earlier images.
Of the two photos used to create the scattering map, the first has a resolution of 1,620 feet (495 meters) per pixel. It was taken 29 minutes before closest approach at a distance of 15,380 miles (24,750 km). The second image was taken approximately 9,940 miles (16,000 km) from Pluto, 18 minutes before closest approach, and has a resolution of 1,050 feet (320 meters) per pixel.
The location of smooth versus rough terrain likely results from the convective flow of nitrogen ice within Sputnik Planum. While the centers of the cells, with some exceptions, are made up of smooth terrain, their edges are rougher and contain more pits. In many cases, the brightest and smoothest areas are actually the boundaries between the cells.
Scientists think that the convective flow of nitrogen ice in this region is akin to the process in a lava lamp, with warmer ice rising in the cells’ centers, then moving outward, and subsequently flowing back down at their edges.
In some areas, the cell boundaries are covered in smooth terrain, a feature that could be caused by the convective system being unstable, with cells continually breaking apart and re-forming. The specific mechanism by which convection creates these patterns in surface textures is not well understood.
Laurel Kornfeld is an amateur astronomer and freelance writer from Highland Park, NJ, who enjoys writing about astronomy and planetary science. She studied journalism at Douglass College, Rutgers University, and earned a Graduate Certificate of Science from Swinburne University’s Astronomy Online program. Her writings have been published online in The Atlantic, Astronomy magazine’s guest blog section, the UK Space Conference, the 2009 IAU General Assembly newspaper, The Space Reporter, and newsletters of various astronomy clubs. She is a member of the Cranford, NJ-based Amateur Astronomers, Inc. Especially interested in the outer solar system, Laurel gave a brief presentation at the 2008 Great Planet Debate held at the Johns Hopkins University Applied Physics Lab in Laurel, MD.