On July 4th, Juno, NASA’s spacecraft readied its engines for a half-hour orbit around the largest gas giant in our Solar System. After a five-year trek to Jupiter, Juno’s orbital mission has finally begun. The common person though wouldn’t necessarily think much of the event. After all, this is not the first spacecraft that made it to Jupiter, nor is it the only spacecraft dedicated to researching Jupiter. However, scientists state that Juno, unlike her predecessors will tell us much more about Jupiter.
Jupiter isn’t considered a gas giant for nothing: it’s huge and big enough to be spotted with the naked eye on a clear night sky. This quality is what allowed astronomers to study it for millennia, taking notes about the things they found interesting about Jupiter. It wasn’t until the 17th century, though, that Jupiter got much more interesting. In 1610, Galileo pointed his telescope toward the gas planet and made the amazing discovery of Jupiter’s multiple moons. At this time, the discovery of the moons was used to solidify the heliocentric theory rather than instigate more study into Jupiter’s nature.
Fortunately, observations on Jupiter persisted through the twentieth century. Astronomers were able to notice colorful cloud bands making their way across the planet, giant spots, and a myriad of new moons. They had also managed to recognize certain gases that existed in Jupiter, including ammonia and methane. However, telescopic observations from Earth to have their limitations. Only seeing Jupiter up close would solve our mysteries about it.
The first missions to send a spacecraft to Jupiter came from the Pioneer Program. Although the Pioneer program was originally known for its failure to send a vehicle to the moon, it’s eleventh mission managed to do something never done before. Pioneer 10, launched on March 3, 1972, was launched on a trajectory that would have it fly by Jupiter on its way out of the Solar System.
Traveling at over eighty thousand miles per hour, Pioneer 10 passed Jupiter’s gas clouds on December 23, 1973. Pioneer 11 did the same a year after, managing to get closer than its predecessor had gotten. Both Pioneers were able to gather up data on Jupiter in ways that hadn’t been done before. Information about Jupiter’s magnetic field, tilt, gravitational pull, cloud layer depths, and rings were all relayed back to Earth. A few years later, Voyager 1 and 2 managed to make more discoveries on the topic of Jupiter’s rings and moons. And this just barely scraped the surface.
The issue with the Pioneer and Voyager crafts were that they were merely flyby spacecrafts. None of them fell into Jupiter’s orbit to get a good look into Jupiter's true nature. This was changed in the 1990s with the Galileo mission.
Galileo was launched from the Space Shuttle Atlantis on a trajectory towards Jupiter on October 18, 1989. The probe was designed to fly into Jupiter and report on the planet’s chemical composition, atmospheric balance, lighting environment, among other things. Galileo had a longer lifetime permitting it to meticulously study the inner workings of Jupiter.
And that it did. Galileo revealed so much about Jupiter’s famous cloud belts and volcanic surface. It also brought light on the water condition on Jupiter. With a closer look at Jupiter, Galileo had rebuked the quantities of water that the Voyager and Pioneer had reported. This correction meant the improvement of planetary formation theories. Unfortunately, Galileo met a sad but fulfilled death in Jupiter’s thick clouds on September 21, 2003.
Juno, however, has made its way to Jupiter and carries the all the hopes of scientists who seek a better understanding of the planet. Scientists claim that it is “an in-depth study that will ultimately help us understand Jupiter’s origin and evolution, which will in turn explain our own Solar System as well as distant ones”. After all, who knows Jupiter more than Juno herself.