A plucky spacecraft named Juno began a long journey to Jupiter today from Florida at 12:25 p.m. EDT despite a small anomaly with its rocket ride and a boat wandering into the launch zone. Named after the mythical Roman goddess and wife of Jupiter, Juno will take about five years to reach the gas giant and slip into orbit. It packs a suite of scientific instruments to study Jupiter, in addition to some Lego figurines. Once there, NASA expects the spacecraft to spend a year making at least 32 elliptical, pole-to-pole orbits before intense radiation bakes its circuits. “From Juno we’re going to go learn about Jupiter so we can start to put together the pieces of how the solar system was made,” said planetary scientist and mission leader Scott Bolton of the Southwest Research Institute in a video. “Jupiter’s got the first clues for us.” Jupiter orbits about 400 million miles away from Earth and is thought to be one of the first planets that formed in the solar system some 4.6 billion years ago. If nothing goes awry during the spacecraft’s trip, Juno will be the ninth spacecraft to visit the gas giant, but only the second to stick around for more than a flyby. The Galileo is currently the sole spacecraft to have orbited Jupiter. Those missions racked up some serious knowledge of Jupiter, but brought up perhaps more questions than they answered. In this gallery are six mysteries Juno may resolve before its radiation-induced death.

How Did Jupiter Form? Jupiter is the sun’s firstborn planet. It is also the biggest and most massive at roughly 318 times heavier than Earth. “If we can understand how Jupiter was made, that helps us understand how the whole solar system was made,” said space scientist David McComas of Southwest Research Institute and member of the Juno mission. “It’s getting really interesting with the discovery of planets around other sunlike stars.” Some models suggest our massive protector formed further away from the sun, then migrated inward. Others posit the gas giant was made about where it is today, and that comets provided its water. Measuring Jupiter’s water content will provide the best clues as to where the planet formed.

How Much Water Does Jupiter Have? When the Galileo spacecraft’s probe plowed through Jupiter’s thick clouds, its instruments looked for the presence of water. For the most part, the clouds it measured were bone-dry -- much like the ones above. “That doesn’t mean the whole planet is like that, however, because it’s one data point,” McComas said. “It’s like if you landed on Earth in the middle of an ocean or desert and determined the entire planet was like that one spot.” Juno won’t launch a probe like Galileo. Instead, it will peer deep into Jupiter’s clouds using radiometers able to measure temperatures. Those temperatures will provide indirect clues as to where the water is and how much is present. With those measurements made, pieces of other mysteries should come together. “Water is a big part of answering some of the how-did-Jupiter-form mystery and, as far as we know, also super important for life,” McComas said. “How Jupiter got its water will help tell us how Earth got its water.”

What is Going On Beneath Jupiter’s Surface? When the Galileo probe fell through Jupiter’s atmosphere, it didn’t get very far before it stopped transmitting data — about 22 bar (1 bar is the pressure of the atmosphere weighing down on Earth at sea level). Juno will monitor vast swaths of the planet from afar and should be able to peer at subsurface layers as deep as 100 bar. The spacecraft will use its radiometers -- also used to measure water content -- to provide the deepest and most complete picture to date of Jupiter’s swirling layers of clouds, perhaps even giant thunderstorms first spied by the Galileo spacecraft (below).

Does Jupiter Have a Rocky Core? Models of Jupiter’s interior abound. Some have rocky cores about 10 times the mass of Earth, but others portray the gas giant without one. “A lot of these models aren’t constrained by actual observations, so it’s a bit of a guessing game,” McComas said. “We should finally get a handle on this with Juno.” During Juno’s elliptically shaped orbits, slight wobbles in the spacecraft’s movement should provide clues about the core’s existence and size. “The spacecraft gets pulled and pushed by Jupiter’s gravity field, and we can sense that through the communication system back to Earth,” Bolton said.

Where Does Jupiter’s Magnetism Originate? Jupiter has an intense and far-reaching magnetic field. Exactly what drives the magnetic powerhouse and how deep inside the planet it originates, however, is unknown. “We generally know it takes a charged fluid moving inside the planet to do this,” McComas said. “Jupiter spins very quickly, about once every 10 hours, and almost all mass of the solar system [not in the sun] is locked up inside the planet.” That fast rotation means a lot of energy rotating cells of hydrogen fluid, and Juno will look for them by mapping the magnetic field in 3-D using a magnetometer.