After a journey that has lasted the better part of a decade, the answer to “are we there yet” is finally “yes,” for NASA’s New Horizons spacecraft. After a brief glitch over the weekend, all systems are once again go for an historic encounter, 3 billion miles from Earth.

Since we discovered Pluto in 1930, we’ve learned all kinds of things about it. That it’s a little smaller than our moon. That it’s mainly rock and ice. That it takes about 247 years to complete one orbit around the sun. And yet, we still don't even know what it actually looks like.

“We could learn a lot about Pluto from the ground with the best telescopes but soon you run into a wall,” said MIT Planetary Science professor Richard Binzel, who has studied Pluto for three decades says “You reach a limit that you just simply can’t answer any more questions until you go there.”

These days Binzel is down at NASA’s science operations center in Maryland as the science team co-investigator for New Horizons, NASA’s first mission to what was once considered our solar system’s last planet.

The Pluto mission has been an effort that has been ongoing for almost 25 years with various starts and stops and has taken a lot of persistence even to finally get the launch pad in 2006.

The plucky spacecraft has traveled nearly 3 billion miles over the last nine years. It’s so far away, it takes 4 hours for a single bit of data, traveling at the speed of light, to reach scientists back here on earth. And the data has been coming in.

“So far we’re seeing that Pluto is even more strange and bizarre than we could have imagined,” says Binzel.

So far we're seeing that Pluto is even more strange and bizarre than we could have imagined

Already, we’ve learned that Pluto has at least five moons, not three. It has huge bright patches and enormous dark spots made of – who knows. The big reveal comes on Tuesday night, when New Horizons will whiz past Pluto at about 7 miles per second, close enough to snap detailed photos of the surface, and measure everything from it’s atmosphere to it’s weather.

“I’m excited to try to get a complete picture of what Pluto is as a world,” says Binzel. “We think Pluto might have seasons, which seems crazy for an object that is roughly 3 billion miles from the Sun right now.”

Over at the BU Astronomy department, professor Paul Withers says the excitement is palpable. Event though Pluto isn’t his specialty, he says that anything new that we learn effects everything else we know – or think we know - about our solar system.

“The solar system really is a very connected series of objects. It’s not just a rock here and another rock a few million miles away,” says Withers. “It’s grown and evolved together in the billions of years since it formed together.”

And the best part?

“The most exciting thing we’re gonna find at Pluto is something we’re not expecting at all,” says Withers.

And really, says Binzel, that’s the whole point. Not since Voyager revealed Neptune in the 1980s have we seen a planetary object for the very first time. And never in human history, have we seen something this far away this closely.

“This is historic exploration,” says Binzel. “Get into it, feel it. This should touch you at your very core of your curious being. It’s that innate human desire to explore that we’re expressing with this mission.”

After its Pluto flyby New Horizons will investigate it’s largest moon, Charon, and then a few of the thousands of objects in Pluto’s neighborhood – the Kuyper belt. Pretty big stuff for a little metal object the size of a grand piano.