July 20, 2015

New Horizons brings Pluto up close and personal

by Bonnie Denmark

All eyes are on Pluto, the latest darling of our galaxy. On the morning of July 14, 2015, the New Horizons spacecraft came within 7,750 miles of Pluto in a historic data-gathering flyby. At a brisk 31,000 miles per hour, New Horizons has traveled 3 billion miles (4.8 billion km) over 9 ½ years and is now phoning home with images that are surpassing the wildest dreams of space scientists. While still nearly a week away from the closest approach to Pluto, New Horizons returned a valentine from the dwarf planet: A heart-shaped feature that dominated Pluto’s surface.

NASA’s New Horizons spacecraft sent this image of Pluto taken on July 13, 2015, when the spacecraft was still almost half a million miles (768,000 km) from the surface. The view is dominated by a large, bright heart-shaped feature, now unofficially named Tombaugh Regio in honor of the American astronomer who discovered Pluto in 1930. The feature measures approximately 1,000 miles (1,600 km) across. Credits: NASA/APL/SwRI

The New Horizons mission was decades in coming, a story of perseverance, dedication, and dreams of testing the human potential. The Pluto story began in 1930 with Clyde Tombaugh, a high school graduate with a love of outer space. He lived on a remote farm in Kansas, where he taught himself astronomy and trigonometry. He built his own telescopes and patiently sketched his observations. His drawings so impressed astronomers at the Lowell Observatory that they invited Tombaugh to work with their new telescope in Flagstaff, Arizona. There, after two years and thousands of hours gathering and studying millions of images of stars, Tombaugh discovered Pluto. (Academy of Achievement, 1991).

Pluto long remained a mystery, a fuzzy blob of light even from the most powerful telescope, but there was little serious discussion of exploring the outermost edge of the solar system. The impetus for unlocking this new frontier came from Alan Stern, planetary scientist at the Southwest Research Institute and New Horizons principal investigator. While still a graduate student in 1989, Stern suggested a Pluto mission to NASA. For many years, a small band of fellow Pluto enthusiasts known as the “Pluto Underground” campaigned for the mission. In 2001, NASA finally approved the project and Stern began assembling a team, which now includes hundreds of scientists, engineers, and technicians, about a quarter of whom are female. Young people were deliberately selected to help ensure that the people who invested so much of their career in the project would be around to see the outcome. (The Year of Pluto, 2015)

New Horizons Principal Investigator Alan Stern of the Southwest Research Institute celebrates with New Horizons Flight Controllers after receiving confirmation that the spacecraft had successfully completed its flyby of Pluto, July 14, 2015, in the Mission Operations Center of the Johns Hopkins University Applied Physics Lab. Credits: NASA / Bill Ingalls

New Horizons set off from Cape Canaveral, Florida, on January 19, 2006, on a mission to collect data and images of Pluto, its moons, and other objects in the Kuiper Belt, the mysterious, icy “third zone” on the outer reaches of our solar system. When the mission began, Pluto was still known as the 9th planet in our solar system, but a mere seven months later it was relegated to the newly-defined category of “dwarf planet”  by the International Astronomical Union to the consternation of the public and many scientists alike. Two years before the spacecraft was launched, Stern stated the mission’s objective (The Year of Pluto):

[T]he key to planetary science is that you really have to go places to get the resolution, to get up close enough to really see what’s going on. We want to get up close and personal. —Alan Stern, New Horizons Principal Investigator, Southwest Research Institute

“Up close and personal” is a fitting description of the stunning images that New Horizons has been sending home. Outfitted with seven of the sleekest scientific instruments available, the spacecraft can record incredibly detailed images, make heat maps, measure solar wind, analyze gases and dust particles, and transmit all the data back to Earth.

Just days after the epic flyby, images from the space probe reveal an amazing, geologically active world with high ice mountains that rival the Rockies, frozen plains, hills, troughs, pits, canyons, and cliffs. New Horizons team members shared images, information, and working theories in a July 15 press conference and subsequent news releases. Among the exciting finds: Pluto is larger and younger than first thought; it is reddish-orange, not the blue seen in textbooks (the color comes from methane gas being acted upon by ultraviolet light); it has a plasma tail formed by nitrogen ions as the atmosphere is being lost to space; and frozen carbon monoxide covers the plains of Pluto’s icy heart.

The icy mountains of Pluto. Close-up images released July 15 of a region near Pluto’s equator reveal a giant surprise: a range of youthful mountains rising as high as 11,000 feet (3,500 meters) above the surface of the icy body. Credits: NASA/JHUAPL/SWRI

The “mind-blowing” data stream will continue for another 16 months, sending scientists on a quest to discover the processes behind Pluto’s atmospheric behavior and landscape features. For example, Pluto’s thin atmosphere is sending scientists looking for evidence of cryo-volcanoes or geysers that replenish nitrogen from an internal source. Also, since Pluto’s geological activity is not fueled by tidal heat (energy that results from gravitational interactions with another body) as on Jupiter, geophysicists are on a quest to find an internal heat source. (To understand the geological processes that form landscape features on Earth, read our module The Rock Cycle.)

To honor one of the last requests of the man who discovered Pluto, New Horizons carries part of Tombaugh’s ashes. Now that the space probe has passed Pluto, it will travel through and then past the Kuiper belt in the coming years. Eventually, New Horizons will carry Tombaugh’s ashes right out of our solar system and out into interstellar space. The discoverer of Pluto once said, “I used to think about how nice it would be to visit the planets.” Now he will be the first person to travel beyond the solar system.



What story will Pluto ultimately tell us? Keep up with developing news on the official site for New Horizons: NASA’s Mission to Pluto, where scientists at Johns Hopkins Applied Physics Laboratory post regular updates.

For more information on the New Horizons mission, including fact sheets, schedules, video and the latest images, visit http://www.nasa.gov/newhorizons

For more on how the New Horizons mission came into being, how it is carried out, and what it hopes to accomplish, watch the NASA documentary The Year of Pluto.

Read about the beginnings of the science of astronomy in our module Description in Scientific Research.

Interested in space science? Read about what astronauts do on manned (and womaned) missions in our profiles of Franklin Chang Díaz and Ellen Ochoa.



Academy of Achievement (1991). Interview with ClydeTombaugh, Discoverer of Planet Pluto: A Man of Universal Wonder. http://www.achievement.org/autodoc/page/tom0int-1

Johns Hopkins University Applied Physics Laboratory. New Horizons: NASA’s Mission to Pluto website. http://pluto.jhuapl.edu/

Johns Hopkins University Applied Physics Laboratory (2006.) Happy 100th Birthday, Clyde Tombaugh: NASA’s New Horizons Mission Salutes Pluto’s Discoverer, born Feb. 4, 1906. http://www.jhuapl.edu/newscenter/pressreleases/2006/060203.asp

NASA’s New Horizons website. http://www.nasa.gov/newhorizons

NASA (2015).  The Year of Pluto. https://www.youtube.com/watch?v=EJxwWpaGoJs


Written by

Bonnie Denmark holds an MA in linguistics and teacher certification in English, ESL, and Spanish. She has devoted her professional life to educational and accessibility issues as a computational linguist, multimedia curriculum developer, educator, and writer. She has also worked nationally and internationally as a language instructor, educational technology consultant, and teacher trainer. Bonnie joined the Visionlearning team as a literacy specialist in 2011, assisting the project by developing comprehension aids for science modules and creating other STEM learning materials.

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