Pluto mania took the world by storm last year when New Horizons flew by Pluto in July 2015. For the first time ever, we were able to see this miniature world up close, and we made some surprising and stunning observations that scientists are still interpreting today.
One of the most significant observations is that there is evidence of surface activity on Pluto. The heart shaped area on Pluto as well as other spots are some of the most reflective surfaces in the solar system, scientists have found. What does this mean? Well, throughout the solar system there are moons and even planets that have what is called "early epoch cratering." These craters were formed long ago, and are still visible today because the surface of the planet hasn't changed. All solid beings in the solar system have been bombarded by other beings at one point. Asteroids smash into each other and into planets. Some smash into each other and coalesce into bigger objects. If the surface of a being in the system is NOT active, the craters from these impacts stay as they are. There would be very few smooth surfaces in the solar system without activity from impacts (things smashing into the body, causing cratering and melting rock), tectonics (the motion of plates in the planet itself, resulting in rifts and volcanoes), or erosion (the wearing away of surfaces via friction of air, particles, or fluids), the three types of planetary activity. The fact that Pluto exhibits one of the most reflective surfaces in the solar system means it has one of the smoothest, and therefore NEWEST surfaces we've seen. It hasn't been hit very much yet by other objects in space.
One thing missing from the equation that suggests surface activity on Pluto is evidence of landslides (which of course might have just been missed--we just did a fly-by, after all). Landslides were detected, however, on Pluto's moon Charon. Landslides like this have been seen on other rocky planets and moons (Mars and Iapetus, most notably), but this is the furthest out in the solar system scientists have seen them, and they are curious to see if other bodies out in the Kuiper Belt have landslides as well.
Pluto exhibits a notable red color, which surprised a lot of people, but this is an indication of the type of material it's made of. Charon's northern hemisphere is also stained red, and scientists think this is material from Pluto that made its way to the moon. The red color comes from chemically processed methane, some of the oldest material in the solar system, which came from Pluto's atmosphere. Scientists believe the methane was caught by gravity and pulled to the surface, where it became frozen to the icy surface. After that, ultraviolet radiation from the sun turned the methane into heavier hydrocarbons, which eventually formed a red organic material called tholins.
The exciting thing is that the discovers of the New Horizons mission may have only just begun. Now that it has passed Pluto, New Horizons is on its way deeper into the Kuiper Belt, one of the least studied areas in the solar system. And its next target, 2014 MU69, also bears that same red coloring, perhaps even stronger than Pluto. New Horizons is set to intercept this small Kuiper Belt Object on January 1, 2019.
Not only have scientists learned more about the surface of Pluto, but they have also seen evidence of potential clouds, which means that Pluto's weather (and at this point, my inner astronomer voice is squeeing, I have to admit--"PLUTO HAS WEATHER!!") is far more complex than scientists imagined.
What does this mean? Well, Alan Stern, the principal investigator from Southwest Research Institute in Boulder, CO, says, "Now, with our spacecraft transmitting the last of its data from last summer's flight through the Pluto system, we know that the next great exploration of Pluto will require another mission to be sent there."
I'm very excited to see what the Kuiper Belt has in store for us, information-wise. We are looking a the building blocks of the solar system when we look at Pluto and Charon, and perhaps even more excitingly when we look at the red tholins, of life itself. Studying these things can help us learn more about how the solar system formed, how life formed, and can answer questions we haven't even thought of yet. But we have to be patient! It's going to be over two years before New Horizons hits its next target!
Have any questions about Pluto, Charon, or the Kuiper Belt? Ask away! I'll be happy to answer anything you throw at me--and if I don't know the answers, I'll interview someone who does!
Melanie R. Meadors is an author and editor of science fiction and fantasy, blogger at The Once and Future Podcast, and a professional author publicist. She studied physics and astronomy at Northern Arizona University, where no day was complete without a heated debate over relativity versus quantum mechanics. You can find her at her website, melaniermeadors.com, on Facebook, and Twitter, @melaniermeadors.