We're all on the cusp of something big.
For the first time in history, a spacecraft will be able to see the possible cliffs and crags of Pluto up close, revealing a new world to humans who have been waiting patiently for more than nine years back on Earth.
On Tuesday, NASA's New Horizons craft will close the gap from its current location millions of miles from Pluto to about 7,800 miles above the dwarf planet's surface for its closest pass of the tiny planet.
People paying attention to space travel in earlier decades were treated to a tour of the major bodies of the solar system by the Mariner 4, Mariner 10 and the Voyager 1 and 2 probes that caught the first close-up views of the planets.
Now, those worlds are as recognizable to us as our own planet, from the clouds of Jupiter to the rings of Saturn.
We've started to understand these planets — and have learned a little more about our own — because of humanity's robotic emissaries sent out into the cosmos. The farther we push out into the solar system and beyond, the more familiar the universe becomes for people on Earth.
But it took until 2015 for Pluto, the mysterious dwarf planet in the outer reaches of the solar system, to get its closeup.
The Voyager probes weren't able to make a flyby of the dwarf planet during their solar system tours in the 1970s and 1980s, and no separate mission was launched to take a look at Pluto until decades later.
NASA had originally planned to fly a mission to Pluto as part of that grand tour of the solar system, but it didn't happen due to budget cuts.
"Really, Pluto fell by the wayside as a result of those budget cuts, 40 years ago now," New Horizons principal investigator Alan Stern told Mashable in an interview.
Pluto was discovered by Clyde Tombaugh in 1930, but since then, it has largely remained enigmatic. The Hubble Space Telescope photographed Pluto and its five moons — Charon, Hydra, Kerberos, Styx and Nix — throughout the years.
Hubble gave us hints of Pluto's surface features and data about its thin atmosphere, but the icy world is so far away that even the powerful space telescope couldn't get a high-resolution look at it. We were still looking at a blurry space object.
We needed to get closer.
Maybe, in some ways, it's a good thing it did take a while. A new generation of people now has the chance to see arguably the last well known solar system object come into view. Humans that weren't alive for (or can't remember) the flybys or landings on other planets now get to see a brand new object revealed for the first time.
Stern, who has worked on New Horizons for more than a decade, estimates that about half of the people in the United States today do not remember, or weren't alive for, Voyager 2's observations of Neptune, meaning that millions of people on the planet today have never witnessed a previously unseen world come into sharp focus.
Even before New Horizons launched on its long journey to Pluto in January 2006, people were excited for the flyby. Along with its imaging equipment and data links back to Earth, New Horizons is carrying a CD filled with an electronic guestbook, containing the names of more than 430,000 people around the world.
Is it over?
But at the same time, when the baby grand piano-sized spacecraft makes its closest approach to Pluto on Tuesday morning, eastern time, it could also be seen as a beginning, rather than an end to a mission.
Yes, once Pluto is explored, all of the major, well-known bodies in the solar system will have been seen at close range.
But there are so many new worlds we have yet to explore, and New Horizons might just open the door to many of them.
Pluto exists in a part of space known as the Kuiper Belt — a group of icy objects outside of Neptune's orbit. By learning more about Pluto itself, scientists could unlock the secrets of a whole class of unexplored objects in our own cosmic backyard, so to speak.
"The Kuiper Belt was discovered in the early 90s, and all of the sudden, Pluto fit into context," Stern said.
"It wasn't just a random, oddball ninth planet that was different from all the others. It became the harbinger, it became the archetype of a whole new class of small planet."
Icy Kuiper Belt objects are thought to be some of the oldest bodies in the solar system, so by learning more about them, we could also find out something about the evolution of every planet, including Earth, in this part of the Milky Way.
It's even possible that New Horizons will get the chance to make a close pass of another object in the Kuiper Belt after it speeds past Pluto, giving scientists a better chance to see what other icy bodies in that part of space are like.
Or perhaps the budget axe, which nixed a Pluto probe four decades ago, will strike again. (A mission extension would require more funds to keep the program going.)
Scientists also think that Pluto isn't exactly a typical kind of small body in the Kuiper Belt either, so visiting another object out there could be beneficial to researchers hoping to learn more about how those bodies behave.
Pluto, the oddball
The flyby should also help scientists learn basic things about Pluto itself.
For example, we don't know exactly what the tiny world's atmosphere is made out of, or the composition of Pluto's patches, some of which are incredibly dark, and others brightly-colored.
"There are regions on the surface [of Pluto] that have to be as dark as anything we've ever seen in the solar system," New Horizons co-investigator Marc Buie told Mashable in an interview.
"At the same time, if you travel on Pluto, if you get in the car and drive 500 or 600 miles to the northeast of that dark region, then you're in a region that is as bright as anything we've ever seen in the solar system, yet it's all the same object," he said.
New Horizons has already sent back incredible images showing surface features that have never been seen before on Pluto. New photos have shown that much of Pluto is not white or blue, but is actually a rusty red color.
For example, a whale-shaped dark patch and a bright white heart-shaped blotch both came into focus in a July 7 image taken by the probe when it was still about 5 million miles from the dwarf planet.
Who knows what other features might be revealed when the craft gets closer?
Is it a planet?
In August 2006, just after New Horizons launched, scientists at the International Astronomical Union's general assembly voted to "demote" Pluto from its status as a "major planet" to that of "dwarf planet." The controversial vote was met with disdain by the public and planetary scientists alike. It made Pluto the underdog and a planetary cult hero.
Stern, for his part, never stopped believing in Pluto's status as a planet, even if it is little.
"A planet is an object in space that is large enough to be called big, therefore a planet. What is the definition of big? Rounded by gravity," Stern said.
"Anything that's big enough to be round, we call a planet, as long as it's not a star."
Major planet or not, mission managers have been waiting a long time to see Pluto, and their patience is about to pay off. Most of the people working with New Horizons today were helping with the development of the mission well before it launched.
"It's really becoming real," Alice Bowman, New Horizons mission operations manager, told Mashable. "It's pretty amazing to be involved in it."
"It’s the first time in 25 years that we’ve approached an unknown world of this size," New Horizons scientist John Spencer told Mashable.
Buie, for his part, has been waiting to see Pluto in focus for most of his professional life.
He has spent days staring at images of Pluto taken by the Hubble Space Telescope to create the best maps of the dark and light areas on the dwarf planet's surface through the years, but those images can't hold a candle to the way New Horizons will see that world.
"On a purely personal level, I have been working on studying Pluto for 30 years, and I have been working with very, very limited data and these are very difficult investigations," Buie said. "Was I right?"
Now, those decades of patience are about to pay off.
Good luck, New Horizons, and thank you for showing most of us a new world for the first time.