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What Has New Horizons Discovered at Pluto?

Leonard Kelley holds a bachelor's in physics with a minor in mathematics. He loves the academic world and strives to constantly explore it.

Artist's depiction of the New Horizons probe in space.

Artist's depiction of the New Horizons probe in space.

Launch and First Encounter

After all the years of preparation and planning that goes into a new space probe, New Horizons finally launched on January 19, 2006, aboard an Atlas V rocket with a Boeing STAR 48B solid rocket motor. Just 45 seconds after liftoff, New Horizons separated from the rocket. It easily became the fastest space probe ever launched, making it to the moon in hours. It even reached faster velocities (up to 35,800 mph!) after its Jupiter gravity assist. Prior to that, New Horizons passed by 2002 JF56, a 4-kilometer-diameter asteroid, on June 13, 2006. NASA took the opportunity to test out some of New Horizons' instruments as it streamed by on its destination to the Kuiper Belt (Stern "The New" 11, Dunbar “NASA," Stern "NASA" 24).

Jupiter as imaged by New Horizons.

Jupiter as imaged by New Horizons.

Jupiter . . . and Beyond

On February 28, 2007, New Horizons finally encountered Jupiter 13 months after its launch. This was incredibly fast—5 times sooner than Galileo and 3 times sooner than Cassini. NASA turned on New Horizons instruments and began to look at Jupiter and its moons while taking pictures as well. Even though the gravity assist occurred the next day, New Horizons continued to observe Jupiter until June of 2007. After the assist, New Horizons now traveled at 35,800 miles per hour on its 3 billion-mile trip to the Kuiper Belt (Stern "The New" 1, 11; Dunbar “NASA," Stern "NASA" 24).

After this flyby, only 2 months of every year saw New Horizons turn on its instruments to ensure that they were operational as it moved to Pluto. Because it took 9 hours for signals to travel from New Horizons to us and back, the probe had to do most of the science collecting automatically. The actual flyby was quick, and the total amount of observational time amounted to a few months. Also, because New Horizons transmitted data at 1000 bits (not bytes!) per second, it took over a year for the full results to even reach NASA (Stern "The New" 11, Fountain 2, Guterl 55).

Pluto and Charon come into view.

Pluto and Charon come into view.

Arrival At Pluto and the Flyby

In January of 2015, New Horizons was woken up to begin its 6-month-long mission on Pluto, which was 135 million miles away when the probe was turned on for the main mission. Using its LORRI equipment, New Horizons began taking pictures of Pluto to help triangulate its position and maintain its course. As the probe neared Pluto, it was also taking data telemetry on particles including solar wind and interstellar dust, and taking additional pictures of Pluto. Pictures from mid-April of 2015 began to show surface details, including a potential polar ice cap. The resolution continuously improved until the best pictures of Pluto ever were taken during the flyby (Johns Hopkins 16 Jan). A brief scare was encountered by all when the probe entered safe mode 9 days before the flyby, preventing science from being collected. Fortunately, the problem (a timing error in preparation for the flyby) was resolved quickly and everything was back on track (Thompson "New Horizons Enters").

The final image before the flyby.

The final image before the flyby.

The days passed by quickly and New Horizons was already beginning to see features which would not be visible as the flyby occurred due to the hemisphere proximity. This included four spots which seem to be connected to each other and spaced at a seemingly regular manner. They are about 300 miles wide altogether and have sharply defined boundaries of light and dark, according to New Horizons program scientists Curt Niebur. Another interesting find prior to the flyby was the size of Pluto was finally determined to be 1,474 plus or minus 4 miles wide. Previous efforts had been thwarted because of Pluto's atmosphere obstructing a definite reading, making the boundaries murky. The official Mission specialist Bill McKinnon of the Washington University in St. Louis and the team came to their measurement based on readings from the LORRI instrument which were also looking out for Nix and Hydra. This makes it the largest KBO known to scientists at this time and also revises its volume and therefore density, having further implications as to its composition. The official value is now 1.86 +/- 0.01 grams per cubic centimeter., pointing to a (roughly) 60% rock and 40% ice make-up. And if this wasn't exciting enough more details emerged about the side that New Horizons would get to image in high-resolution, including what seemed to be a giant heart! (John Hopkins 11 Jul, John Hopkins 13 Jul, Chang, Stern "The Pluto" 26).

False color image of the surface.

False color image of the surface.

Download and Be Amazed

As New Horizons flew past Pluto and Charon at 30,800 miles per hour on July 14, 2015, its closest approach was at 7:49 am eastern time at 7,690 miles, just 74 seconds early and only 45 miles off the projected distance! Of course, to ensure that the flyby was a maximum gain event the New Horizons probe did not transmit any data until the flyby was well over, instead focusing all efforts on collecting as much info as possible. Scientists like Alan Stern had to wait over 13 hours post-Pluto flyby to know if New Horizons had even survived or had fallen victim to a possible space collision. But it had indeed made it through and started to send some amazing pictures that blew scientists away (Boyle "Its", Chang).

The RALPH Image.

The RALPH Image.

Within that initial download on the same day as the flyby many discoveries were made. The 3-filter color images that the RALPH instrument was able to capture shows differentiation in the surfaces not visible in the visible spectrum. Interestingly it shows that Pluto's "heart" is not a whole feature but rather two distinct halves made of different materials with one side being smooth and made of carbon monoxide ice (possibly indicating a young age) and the other full of craters (possibly indicating an old age) (Stern "The Pluto" 25, Boyle "New From," Talcott, Hupres).

Methane Madness

Shortly after the first image of Hydra was released, a methane map of Pluto was displayed from infrared measurements. The different colors refer to the different types of methane ice present on the dwarf planet. Other surface measurements indicate that it is all ice and is 90% nitrogen and 10% methane. The different colors seen could be due to particulates like tholin (which absorb blue light and reflect red like most organic materials), the age of the ice, or concentrations of nitrogen and methane (Freeman, Yuhas, Stromberg, Betz "Pluto's Bright", Thompson "First," Hupres).

Methane ice map generated by the Ralph/LEISA instruments, with purple indicating strong readings.

Methane ice map generated by the Ralph/LEISA instruments, with purple indicating strong readings.

Water Everywhere!

Near the end of January 2016, the New Horizons team released a false-color map of Pluto's surface uncovered by LEISA to show how water is distributed. The image below shows all the water on the surface. While the map shows more water than scientists suspected there was, it also points out an interesting absence of the material in Sputnik Planum and Lowell Regio, perhaps indicating how their age plays a role in the surface of Pluto. Also, water levels on this map corresponded to the red areas on the dwarf planet, perhaps indicating a correspondence to tholins and water production (NASA "Pluto's Widespread," Betz "Pluto Surprises").

A water map of Pluto.

A water map of Pluto.


In another first, Pluto became the first Kuiper Belt object to emit X-rays! Yes, as unlikely as it seems like it should be the dwarf planet is sending them out, but how? No one knows, for nothing energetic enough to produce them should happen that far out in the solar system. Why? Not enough solar wind nor a strong magnetic field (Hrala).

The Far Side of Pluto

Even though New Horizons zipped past Pluto in a hurry, it still had time to turn its cameras back and look at the far side of the dwarf planet. This was of course a dark place, not receiving light from the Sun to illuminate it. Fortunately, Charon was able to reflect light onto this, owing to its relatively large size when compared to Pluto as well as its great proximity. After moderate image processing, some details were found. For starters, it appears as though a nitrogen or methane ice deposit exists, due to a brighter than average spot seen. Also interesting was a darker-than-expected south pole, possibly hinting at seasons! (Crane "We")

Next Target: Arrokoth

At the end of August 2015, NASA announced that the follow-up to Pluto would be 2014 MU69, an object over 1 billion miles past Pluto, so long as it passed inspection and review. That was achieved on July 1, 2016. At a little under 30 miles long, it was one of 5 objects spotted by Hubble in 2014 as the New Horizons team was searching for the next phase of the mission. Targeted fuel burns got New Horizons to MU69 by January 1, 2019. Another window into the mysterious Kuiper Belt was revealed. To learn more, check out my follow-up over on my profile (NASA "New Horizons Selects," Wenz, NASA "NASA Releases").

Works Cited

Betz, Eric. "Pluto’s bright heart and Charon’s dark spot revealed in HD." Kalmbach Publishing Co., 15 Jul. 2015. Web. 18 Aug. 2015.

---. "Pluto Surprises With Blue Skies, Red Water." Astronomy Jan. 2016: 16. Print.

Boyle, Alan. "It's Pluto Flyby Day! Get In on the Climax of NASA's New Horizons Mission." NBC Universal, 14 Jul. 2015. Web. 17 Aug. 2015.

---. "New From New Horizons: 5 Things We Just Found Out About Pluto and Charon." NBC Universal, 14 Jul. 2015. Web. 18 Aug. 2015.

Chang, Kenneth. "NASA’s New Horizons Spacecraft Zips Past Pluto in Flyby." The New York Times Company, 14 Jul. 2015. Web. 17 Aug. 2015.

Crane, Leah. "We have had a good look at Pluto's dark side for the first time." New Scientist. New Scientist, 13 Nov. 2021. Print. 16.

Dunbar, Brian. "NASA's Pluto Mission Launched Toward New Horizons." NASA. NASA, 19 Jan. 2006. Web. 07 Aug. 2014.

Fountain, Glen H., David Y. Kusnierkiewicz, Christopher B. Hersman, Timothy S. Herder, Coughlin, Thomas B., William T. Gibson, Deborah A. Clancy, Christopher C. DeBoy, T. Adrian Hill, James D. Kinnison, Douglas S. Mehoke, Geffrey K. Ottman, Gabe D. Rogers, S. Alan Stern, James M. Stratton, Steven R. Vernon, Stephen P. Williams. “The New Horizons Spacecraft.” arXiv:astro-phys/07094288.

Freeman, David and Eliza Sankar. "Dazzling New Pluto Photos Are The Best Ever Taken Of The Icy Dwarf Planet." Huffington Post, 15 Jul. 2015. Web. 18 Aug. 2015.

Guterl, Fred. “Journey to the Outer Limits.” Discover: March 2006: 53-5. Print.

Hrala, Josh. "Pluto is emitting X-rays, and it's challenging our understanding of the Solar System." Science Alert, 18 Sept. 2016. Web. 23 Jan. 2017.

Johns Hopkins University Applied Physics Lab. "How Big Is Pluto? New Horizons Settles Decades-Long Debate." Kalmbach Publishing Co, 13 Jul. 2015. Web. 17 Aug. 2015

---. "New Horizons begins first stages of Pluto encounter." Kalmbach Publishing Co., 16 Jan. 2015. Web. 08 Feb. 2015.

---. "New Horizons' last portrait of Pluto's puzzling spots." Kalmbach Publishing Co., 11 Jul. 2015. Web. 17 Aug. 2015.

NASA. "NASA Releases Record-Breaking Photos From Beyond Pluto." Kalmbach Publishing Co., 14 Feb. 2018. Web. 20 Mar. 2018.

---. "New Horizons selects Kuiper Belt target." Kalmbach Publishing Co., 31 Aug. 2015. Web. 09 Sept. 2015.

---. "Pluto's Widespread Water Ice." Kalmbach Publishing Co., 29 Jan. 2016. Web. 10 Mar. 2016.

Stern, Alan. "NASA Sets Its Sights on Pluto." Astronomy: Feb. 2015: 24-5. Print.

---. "The New Horizons Pluto Kuiper Belt Mission: An Overview with Historical Context." Space Science Reviews 140.1-4 (2008): 3-21. Web. 07 Aug 2014.

---. "The Pluto System Explored." Astronomy Nov. 2015: 25-6. Print.

Stromberg, Joseph. "New Horizons' photos from the Pluto flyby are finally here — and they're amazing." Vox Media, 15 Jul. 2015. Web. 18 Aug. 2015.

Talcott, Richard. "Pluto and Charon show craters, dark spots, and even signs of snow as New Horizons flies by." 14 Jul. 2015. Web. 18 Aug. 2015.

Thompson, Amy. "First Pluto data reveals lots of terrain that is “not easy to explain” ars technica. Conte Nast., 17 Jul. 2015. Web. 19 Aug. 2015.

---. "New Horizons enters safe mode 9 days before Pluto rendezvous." ars technica. Conte Nast., 05 Jul. 2015. Web. 17 Aug. 2015.

Wenz, John. "New Horizons May Visit Twice the Object for the Same Price." Kalmbach Publishing Co., 04 Aug. 2017. Web. 27 Nov. 2017.

Yuhas, Alan. "Nasa unveils 'surprise' Pluto photos and New Horizons discoveries – as it happened." Guardian News, 15 Jul. 2015. Web. 18 Aug. 2015.

© 2015 Leonard Kelley


Leonard Kelley (author) on September 27, 2015:

By all means. I never mind someone citing a hub of mine.

Ruth Mata from New Mexico on September 27, 2015:

I am definitely going to look for that Hub, I may even reference it in the one I am currently writing, if that is okay?

Leonard Kelley (author) on September 26, 2015:

I have a hub on the Nice Model which discusses a bit of how that period may have arose. It will be nice to see a hub that goes into the whole story!

Ruth Mata from New Mexico on September 26, 2015:

I'm currently composing a new hub. This topic will be on the Late Heavy Bombardment, as well as other impacts that greatly affected and shaped our solar system.

Leonard Kelley (author) on September 23, 2015:

I don't know about more knowledgeable but certainly enthusiastic!

Ruth Mata from New Mexico on September 22, 2015:

Well i do have a gmail account :) ruth.eliza beth.angel@gmail com

It would be great to get to talk with someone with an equal admiration in astronomy and physics. And since you're more knowledgeable within the subjects than I am as of current, I feel I could learn quite a bit in the exchange of ideas and theories

Leonard Kelley (author) on September 22, 2015:

I do have a Google Plus website promoting this site but other than that this is it. It would be great though!

Ruth Mata from New Mexico on September 22, 2015:

1701TheOriginal, Do you have social media of any kind? I think it would be great to exchange ideas with you :)

Ruth Mata from New Mexico on September 14, 2015:

As am I. :)

Leonard Kelley (author) on September 14, 2015:

Thanks Ruth. I am even more excited for the data we haven't seen yet.

Ruth Mata from New Mexico on September 13, 2015:

Excellent work. The New Horizon's was revolutionary to our outer planetary research, I was thrilled to see high definition photo's of Pluto for the first time when the probe arrived.