Astronomers have been excited about Jupiter for over 400 years, but there’s always something new to learn!

So back in 2012, the European Space Agency announced a new mission to explore Jupiter and its moons. It’s called the Jupiter Icy Moons Explorer, or JUICE for short.

Because, you know... Jupiter is just a big orange and you want to squeeze it for its data! And as of this month, it’s still on schedule to launch in 2022.

But there's a lot of engineering to do before then. Any spacecraft that visits Jupiter has to be carefully designed, because conditions are so dangerous nearby. For one, Jupiter’s magnetic field is 20,000 times stronger than Earth’s, and it has really harsh radiation belts.

That means any scientific instruments on JUICE can be easily damaged without the right protective materials. And since Jupiter is much farther from the Sun, the spacecraft will need almost 100 square meters of solar panels to keep it powered. These requirements, plus other restrictions about visiting planets like making sure no microbes hitch a ride on the spacecraft means a huge project for ESA engineers.

But earlier this month, they finished the preliminary spacecraft design, including what instruments will be on board, like cameras, sensors, and radio-science experiments, and how they’ll all fit together. And this means they can start building a prototype for testing! They’ll have to simulate the extreme conditions of the launch and of space itself to make sure JUICE can survive, and the spacecraft design will probably change during the process.

But this is still a big milestone in getting the project off the ground! Which eventually will actually happen! Once JUICE gets to Jupiter in 2029, it will spend three and a half years studying its atmosphere, magnetic field, rings, and moons.

It’ll even spend eight months in orbit around the moon Ganymede, and that’ll be the first time we’ve ever orbited any moon besides our own! Some of their objectives include mapping Ganymede’s surface, studying its interactions with Jupiter, and exploring how its interior developed, since it likely contains a huge saltwater ocean. So while NASA’s Juno mission continues its research, with its own mission objectives, ESA engineers will keep working hard to get JUICE off the ground!

Elsewhere in the solar system, it looks like we’re still debating whether or not Pluto is a planet. Will it ever end? This week at the 48th Lunar and Planetary Science Conference, scientists on the team from the New Horizons mission to Pluto presented their argument for why Pluto should officially be a planet again.

Except this time, they went one step further actually more like 100 steps further. They proposed a new definition of the word “planet” that would not only include Pluto, but also over 100 other bodies in our solar system! The IAU, or International Astronomical Union, is responsible for naming objects like planets and comets.

Right now, there are three requirements for an object to be a planet: It has to orbit the Sun, have enough mass so that it’s basically a sphere, and it has to clear other objects, like asteroids or debris, from the neighborhood around its orbit. According to the New Horizons team, there are problems with that definition for one, it doesn’t include exoplanets or rogue planets without a parent star, because these don’t orbit the Sun. They also argue that, since asteroids are constantly crossing through the orbits of the planets in our solar system, none of them have technically cleared their orbits of debris.

Whether or not a planet can clear its orbit is also affected by the Sun’s gravity. So even an Earth-sized planet wouldn’t be able to do it if it were farther away from the Sun, like in the Kuiper Belt with Pluto. So the researchers proposed their own definition: A planet is a body less massive than a star that has never experienced nuclear fusion and that has enough mass to be roughly sphere-shaped.

In other words, planets are round bodies with less mass than stars. They only based their definition on the qualities of the object, not how it interacts with other things, like the IAU’s current definition. Still, even if the old definition is a little outdated, this new definition would add over 100 new planets to our solar system, including Pluto and Charon — but also including our moon!

Don’t start printing up your new, giant, planet flashcards deck just yet, though, because it’s not likely the IAU will accept this new definition. So, sorry, Pluto fans. We may have learned a lot about Pluto and Charon thanks to the New Horizons mission, and we’ll continue to study them and lots of other really great objects in our solar system and in space!

But that doesn’t mean they’ll be official planets anytime soon. Even though we’re… somehow… still arguing about it. Thanks for watching this episode of SciShow Space news, and thank you especially to our patrons on Patreon, who make this all possible!

If you’d like to help us keep making episodes like this, go to patreon.com/scishow and see what that’s all about. And don’t forget to go to youtube.com/scishowspace and subscribe!