If all has gone according to plan, by the time you read this, New Horizons will have passed the last unseen planet in the solar system.

At 7:49:58 am Eastern, the little spacecraft will pass Pluto at 7,750 miles, a distance just shy of Earth's diameter, and the closest it will ever get to the dwarf planet. A few hours later, New Horizons will turn back toward the inner solar system and send a simple message home: Mission accomplished.

The journey has taken more than nine years. New Horizons launched from Cape Canaveral atop an Atlas V rocket in 2006, after a speedy four-year construction. Prior to that, the so-called Pluto Underground spent more than 15 years trying to get NASA to greenlight the project.

Since launch, the small probe has traveled for 3,463 days and 2.97 billion miles—about 32 times the distance between the Earth and the sun. When New Horizons left, a Super Nintendo game offered better resolution than our best images of Pluto. Though the best are still to come, the probe already has sent back color pictures measured in megapixels.

But this is mere icing. The rest of the cake won't come out of the oven for another 18 months. Downlink speed is slow—about two kilobytes per second—and it takes four hours for a signal to reach Earth.

So far, New Horizons has only sent back the tiniest fraction of the data it will collect. But let's take a moment to revel in all we've learned so far. During the last few days, New Horizons has treated us to increasingly detailed images of the geography on Pluto's surface. Astronomers didn't even know Pluto's true size until yesterday. "We are already seeing complex and nuanced surfaces that tell us of history of these two bodies that is beyond our wildest dreams on the science team," says Alan Stern, the mission's principal investigator.

But to those watching carefully, those details are staggeringly slim. You're hungry for information. The scientists are hungry for information. Every single person in the Pluto press corps is starving for information. The crumbs we've been given so far are so sweet, but feel like empty calories.

There's a reason nothing is very substantial, and it's not because NASA is trying to whet our appetites for more. Every bit of information that these scientists give out must be weighed against what's to come. Speculate too much, and bringing the information back in will take twice as much effort. "We know that there’s better energy and imagery and spectra coming in the days ahead," says Kimberly Ennico, New Horizons' deputy project scientist.

The New Horizons team will spend the coming days, weeks, and years analyzing the data streaming back across the solar system. What do we stand to learn?

For certain, we'll learn more about Pluto's geology. Pluto is especially valuable because it's the only other dual planet system in attainable reach. Pluto and its main satellite, Charon, are the only other planets thought to have formed the same way as Earth and its Moon: catastrophic collision. The geologic differences between Pluto and Charon could provide insights to our own dichotomous planetary system.

And within the system itself, there are so many unanswered questions. Pluto's nitrogen-rich atmosphere is leaking into space, but scientists don't know at what rate, or by what mechanism (if any) it is replenished. New Horizons already is encountering escaped nitrogen. "This may mean that Pluto's escape rate is higher than we thought," says Stern. Astronomers here are pondering even weirder questions: Does Pluto have a ring system? Does it share its atmosphere with Charon? New Horizons' infrared imager, radio dish, and plasma spectrometer could provide answers.

That doesn't even begin to cover New Horizons' life after Pluto (assuming it survives the encounter). After it sends back its data, New Horizons will change course and head to the Kuiper belt, our solar system's third region—a trove of comets, asteroids, and more than 100,000 objects sufficiently large enough to be considered worlds.

NASA will begin teasing at those finer points Wednesday morning, when New Horizons begins dumping data in bulk. Until then, we'll all look forward to what's possibly the most important transmission of all. At approximately 8:53 pm ET the probe will transmit some equipment updates, telemetry, and packets indicating its roll, pitch, and yaw. Seemingly boring stuff, but in the context of where New Horizons has been and what it has done, it is the equivalent of an interplanetary A-OK sign saying, "Guys, I've made it."