Galileo and the Exploration of Jupiter

Artist Impression of Galileo encountering Io

On October 18, 1989, the unmanned NASA spacecraft Galileo was launched on her mission to study the planet Jupiter and its moons. Named after the astronomer Galileo Galilei, it consisted of an orbiter and entry probe, which descended into Jupiter’s atmosphere.

It was Galileo Galilei, who connected us to the skies in 1609, when he demonstrated the improved instrument “for seeing things far away as if they were nearby” by Hans Lippershey – the telescope. In this period, scientists began dreaming of observing the stars and planets more detailed and more target-oriented than ever. Only a few centuries after, mankind began traveling into space as Jules Verne in 1865 already predicted. After the first successful moon landing, scientists needed further goals even farther away to explore the universe and its origins. It was worth it traveling to Jupiter for more than six years and even more years of development and construction efforts in order to gather better information. The spacecraft Galileo was supposed to collect the most detailed data on Jupiter, its moons and the many active volcanos and icy terrains on them.

Work on the spacecraft began already in 1977 just before Voyager 1 and 2 were about to launch. Galileo’s mission was originally named Jupiter Orbiter Probe and was scheduled to launch in 1984. Due to several re-developments and technological changes, the launch was rescheduled to 1986 on-board of the Atlantis spacecraft, but further changes forced the NASA to postpone the launch to October 18, 1986. As the the Atlantis climbed into the sky at the Kennedy Space Center Florida, the team on the ground was filled with hope to gather the most detailed information on Jupiter and its moons ever collected.

The four largest Jupiter moons

During its flight, Galileo did certainly not have enough power sources to get to Jupiter directly. The NASA “borrowed” energy through swing-by’s at Earth and Venus to slingshot the spacecraft to the distant Jupiter. On its way, Galileo took very detailed images of the asteroid belt, especially of asteroid Gaspra and in 1994, the spacecraft could perfectly “watch” Shoemeker-Levy 9‘s crash into Jupiter and delivered the only images of the direct impact as Earth-based telescopes had to wait until they rotated into the right view.

In July, 1995 the spacecraft’s probe was sent out to a solo flight, slicing into Jupiter’s atmosphere and releasing its parachute. Meanwhile, detailed weather data could be collected and it became clear that Jupiter’s atmosphere was a lot drier than expected. The probe recorded numerous thunderstorms with lightning strikes up to 1000 times more powerful than those on Earth. The spacecraft also investigated the four largest moons Ganymede, Callisto, Io and Europa and showed that especially Io has great volcanic activities. It was furtherly found out that the volcanic eruptions were quite similar to those of Earth’s early days. The data was then taken to explore conditions on Earth 3 billion years ago. During the mission, Galileo returned over 15000 pictures and next to Gaspra, it managed to view another asteroid, Ida that even had its own moon called Dactyl. It was the first known moon of an asteroid.

At yovisto, you may like the video lecture by Professor Ian Morrison. He presents the talk ‘Voyages to the Outer Solar System‘ at Gresham University.


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