What Did We Learn About Pluto?

Article written: 31 Aug , 2015
Updated: 24 Feb , 2017
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We’ve only had blurry images of Pluto up until New Horizons. So what did we learn when we got up close and personal with Pluto and its moons?

Clyde Tombaugh first discovered Pluto in 1930. He saw only see a single speck of light moving slowly in front of the background stars as he flipped photographic plates back and forth. Sadly, this was the best anyone could do for decades. Even the mighty Hubble, the most sensitive instrument ever focused on Pluto, could only resolve a few grainy pixels.

It’s because Pluto is really really far away: 7.5 billion kilometers. Just the light alone from there takes over 4 hours to reach us. In order to get any more information, humanity needed to reach out and send a spacecraft to Pluto, and photograph it, up close and personal.

In 1989, Alan Stern and a group of planetary scientists began working on a mission. Their work culminated in NASA’s New Horizons spacecraft, launched in 2006, beginning a 9 and a half year journey. And unless you’ve been living in a lunar lava tube, you know that New Horizons finally reached its destination in mid July 2015, passing a narrow 12,472 kilometers above the surface.

For the very first time in human history, we saw a member of the Kuiper Belt right up in it’s business. And now I retire these old low quality images Pluto! Begone artist’s illustrations!

From here on out, we’re all about sick high def photos of the surface and its moons. I for one am going to revel in them for a while.

So fashion shoots aside, what did we actually learn about Pluto? The primary mission was to map the geography of Pluto and its biggest moon, Charon. It would study the surface chemistry of these icy worlds, and measure their atmospheres, if they even exist at all.

The mission had a few other objectives, and of course, planetary scientists knew that the spacecraft would just surprise us with stuff we never expected. Kuiper Belt objects like Pluto and Charon are ancient; geologists expected them to be pockmarked with craters, large and small.

Views of Pluto during New Horizons' approach. Credit: NASA/Damian Peach

Views of Pluto during New Horizons’ approach. Credit: NASA/Damian Peach

Surprisingly, New Horizons showed relatively smooth surfaces on both worlds. Pluto has a Texas-sized region newly named Sputnik Planum, where exotic ices flow like glaciers. Frozen nitrogen, carbon dioxide and methane ices act just like the ones we have here on Earth. We can see from the relative lack of craters that this process is still happening.

Pluto has mountains. Mountains! Close ups show a young range with peaks as high as 11,000 feet, or 3,500 meters. Here’s the crazy part. Those exotic chemicals that act like snow and ice? They’re not hard enough to make mountain peaks like this.

At extreme cold temperatures, water ice becomes as hard as rock. These mountains are made of ice, and they’re very young, probably less than 100 million years old. There could be plate tectonics on Pluto, but with ice, not rock. My mind is blown.

Pluto’s moon Charon has a huge chasm longer and deeper than the Grand Canyon in Arizona and although scientists hoped to see an atmosphere, the reality was beyond anyone’s expectations.

Backlit by the sun, Pluto’s atmosphere rings its silhouette like a luminous halo in this image taken by NASA’s New Horizons spacecraft around midnight EDT on July 15. This global portrait of the atmosphere was captured when the spacecraft was about 1.25 million miles (2 million kilometers) from Pluto and shows structures as small as 12 miles across. The image, delivered to Earth on July 23, is displayed with north at the top of the frame.  Credits: NASA/JHUAPL/SwRI

Backlit by the sun, Pluto’s atmosphere rings its silhouette like a luminous halo in this image taken by NASA’s New Horizons spacecraft around midnight EDT on July 15. This global portrait of the atmosphere was captured when the spacecraft was about 1.25 million miles (2 million kilometers) from Pluto and shows structures as small as 12 miles across. The image, delivered to Earth on July 23, is displayed with north at the top of the frame. Credits: NASA/JHUAPL/SwRI

New Horizons detected a thin nitrogen atmosphere at Pluto. It could be snowing nitrogen on Pluto right now. There could be faint winds, since there are regions on Pluto that look like they might have undergone weathering.

Take a look at this photograph as New Horizons zipped away. You can see the atmosphere clearly surrounding the dwarf planet, interacting with the solar wind and creating a tail that stretches away from the Sun.

Here’s my favorite thing we learned. Pluto is about 80 km larger than previous estimates, which makes it the largest Kuiper Belt Object found so far. Even bigger than Eris, which is still a little more massive. So maybe it’s time to revisit that Pluto planethood debate again. I’m just messing with you. No good will ever come from having that debate. It will only end in tears.

Interestingly, the data connection between Earth and New Horizons is tenuous. Possibly the worst internet since AOL. It can only transmit back about 1kb of data per second, which means that we’ll need to wait about 16 months for the photographs and data to be sent home during the first few days of the flyby.

As an extra bonus, this isn’t the last we’re going to hear from New Horizons. Because it’s so far away, as the spacecraft can only trickle data back to Earth. It’s going to take almost 2 years for all the images and measurements it gathered during its flyby to get back to Earth for scientists to study. Expect many more discoveries and announcements over the coming years, and more videos from us.

Now that Pluto has finally been explored, where do you think we should go next in the Solar System? Tell us in the comments below.

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5 Responses

  1. laurele says

    I hope we do revisit the debate over Pluto’s planethood, which has remained active since its discovery and especially over the past nine years.

    How about a follow up mission to Pluto to answer all the questions the data from New Horizons will raise? It would be great to have an orbiter or at least a flyby of the other side of Pluto, of which we did not get high resolution images.

    We should visit the other dwarf planets as well, plus send orbiters to Uranus and Neptune. How many missions could be funded with the money spent on decade-long wars in Iraq and Afghanistan?

  2. There is no guarantee the debate will end in tears. That is not how Science is conducted, anyway. The current definition of a planet is absurd, and need to be revised. End of story. Dwarf stars are stars. Dwarf galaxies are galaxies. Most cashews consumed worldwide are dwarf cashews, even. The IAU was wrong to exclude dwarf planets as a subcategory. If you are an American, need I remind you we are the home of the brave? Wipe away your tears and walk with Pluto!

    To answer your question, I would like to see a follow-up mission to Pluto and a trip to Haumea.

  3. Malus says

    What is the possibility of ever returning to Neptune or Uranus for further study?

  4. Gaugain says

    the debate on Pluto Planet is coming from another problem: the inability of the average american to remember the names of more than 8 planets. To understand how weird is that we have to see the way they try to remember their names: by inventing a phrase that contains all the initials of 8 planets (the limit i told you about). So instead remembering 8 or 9 planets by name, you must remember a phrase , take the initials of every word and try to remember what planet reveals every initial…how weird is that ?

    • laurele says

      There is no need to memorize a list of names. We don’t ask kids to memorize the names of all the rivers or mountains on Earth, just to know what makes something a river or mountain. Memorizing planets dates back to the days when we knew little else about them other than their names. Today, it is more important for kids–and adults–to learn the different subtypes of planets and their characteristics.

      While memorizing isn’t important here, it’s also not true that Americans can’t memorize more than eight or nine names. Many kids successfully learn and memorize the names of all 50 US states in school. My nephew’s class did that in first grade.

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