Genre: Information/Explanation

The Juno spacecraft arrives at Jupiter on July 4 , 2016 , after a journey of nearly five years and 2.7 billion km ( 1 . 7 billion miles ) . It will be the first space probe to orbit Jupiter since Galileo plunged into that planet's atmosphere in 2003 . NASA / JPL-Caltech Jupiter is the most-massive planet in the solar system , and because it is so large , it retained all of the gas it was born with . Nothing could escape its gravitation by seeping into space , like the hydrogen in Earth's atmosphere . By studying the composition of Jupiter , Juno will be able to identify the gas that the planet formed with 4.5 billion years ago and thus maybe learn how Jupiter came to be . NASA / JPL The Great Red Spot is a storm larger than Earth ( about 16,500 km wide ) that has been swirling since at least the 1830s and maybe even since the mid-17th century . Although it 's been observed for centuries , almost nothing is known about it . What is powering it ? Why has it lasted for hundreds of years ? Juno will get a very close view of the spot , from just 4,600 km ( 3 , 000 miles ) away , which may clear up its mysteries . Not much is known about the core of Jupiter , or even if it really has one at all . Scientists have speculated that Jupiter's core is likely hydrogen that has been squeezed by the enormous weight of the atmosphere above it into a metallic form . As the probe's velocity changes as it orbits the planet , the frequency of radio waves that Juno transmits to Earth will change . From these changes , Juno will measure Jupiter's gravitational field and its internal structure precisely . NASA / JPL / Johns Hopkins University Applied Physics Laboratory Jupiter has the largest magnetosphere of any planet . The magnetic field lines stretch out over a space 75 times bigger than the planet itself . Juno is teeming with instruments to study the charged particles trapped in Jupiter's magnetic field . These measurements – when combined with the study of Jupiter's deep internal structure , where the magnetic field is generated – will give a much better understanding of this powerful magnetosphere . NASA / JPL / Space Science Institute Juno will be in a polar orbit around Jupiter in order to avoid encounters with the planet's strong radiation belts , which could damage the spacecraft . Thus , Juno will be the first probe to get a close-up view of Jupiter's poles . The polar regions of Jupiter are very interesting because of Jupiter's powerful magnetosphere , which generates strong aurora . The auroral oval even has spots from which currents of plasma flow from Jupiter's moons to the poles of the planet .