EXPERT REACTION: Juno's Jupiter jaunt

Because it is so massive, Jupiter had a huge impact on the evolution of our Solar System - this means understanding Jupiter is crucial to understanding the Solar System. Juno will shed light on different formation scenarios and, by determining the early structures that kickstarted the planet–making process, give new insights into the question  how did we get here?

To do this required an immense amount human endeavour, creativity and intelligence. Combined with the Pluto New Horizons mission, we are witnessing some of the most significant events in the history of space exploration. NASA continues to impress.

Juno aims to deepen our understanding of Jupiter -- its formation and evolution -- and help us learn more about planet formation. After a 5-year journey travelling through space, Juno has successfully obtained orbit around Jupiter and is ready to begin its science goals. Juno will use its instruments to investigate properties of Jupiter, such as its atmosphere, its magnetic field and its gravitational field, with a goal to learn about Jupiter's internal structure and to shed light on how it formed. Jupiter's enormous size suggests that it has played a critical role in the formation of our Solar System. Similarly, large gas giants like Jupiter in other systems may also influence the formation of those systems, and so learning about Jupiter's birth and evolution will help us not only understand the formation and history of our own Solar System, but also the history of others.

It has been exciting to watch the nearly five year journey to Jupiter, surviving the harsh environment of the radiation of space and the rocks around Jupiter. The current orbit, or rather the reached orbit of 53.5 days, was crucial to avoid the radiation belts around Jupiter, and be in a gravitationally stable orbit with Jupiter. Had it not reached this level, and perhaps ended up going too close, it would have not be able to orbit for as long.
 
I’m quite excited about the measurements of the core of Jupiter, allowing us to figure out what the core of these gas giants are. Moreover, given how closely Jupiter resembles  a Brown Dwarf star, it is a good chance to get some analogues of these types of stars too.

It’s a stunning effort by all at NASA and the Juno team to reach Jupiter. After a 2.8 billion km journey, the spacecraft had to hit a target just 20 km across, akin to hitting the bulls-eye from the other side of a city, all on autopilot. This five year journey could easily have ended in disaster as the spacecraft passes just 5,000 km above the cloud-tops; to get a sense of scale, this is skimming just 8 mm above the surface of a basketball. The reason it’s going so close is to duck beneath the deadly radiation belts that surround the equator of Jupiter like a doughnut. Even then, the spacecraft will receive 100 million dental X-rays-worth of radiation by the time the mission ends, but for now the hard bit is over and the team can relax before the next plunge towards the planet in just over a month.

I can’t wait for the science to begin! We will learn about what Jupiter is made of, revealing how and where it formed in our Solar System. We will learn whether it has a solid core or if you’d fall into ever-thicker and denser clouds if you were to fall into Jupiter. There may even be a strange form of metallic hydrogen which is what hydrogen gas turns into when subject to enormous pressures deep inside the gas giant. All of these mysteries will be revealed in the coming years now that Juno has safely reached the King of the Planets.