Galileo Cruises the Inner Jovian System

The Galileo spacecraft, which has been orbiting Jupiter since 1995, will crash into the planet on September 21, 2003. The crash is not an accident! Scientists want to make sure Galileo will never accidentally crash into Jupiter's moon Europa, so they are destroying the spacecraft by crashing it into Jupiter. Scientists think there could be life on Europa, so they want to make sure that any microbes from Earth that may be riding on Galileo cannot infect Europa. Since the team of scientists and engineers controlling Galileo knew that it would be destroyed, they decided to send Galileo on a risky orbit close to Jupiter in November 2002. The space near Jupiter is filled with deadly radiation, and Galileo had stayed away from that area earlier in its mission. Mission planners didn't want Galileo to get fried! But on November 5, 2002, Galileo swung very close to Jupiter, deep within the planet's powerful radiation belts. Galileo was able to collect new data from this region that had never been measured before!

The animation below shows some of the information Galileo gathered on the November 2002 encounter (known to Galileo mission team members as the the "A34 pass"). You will need to have the latest version of the Flash player to see this animation. There is more information about the features shown in the animation further down this page.

The animation shows the area close to Jupiter. Jupiter has moons; the five closest to the planet (Adrastea, Metis, Amalthea, Thebe, and Io) are shown here. Jupiter also has a series of rings, like the famous rings of Saturn. Jupiter's rings are much fainter and smaller than are Saturn's. Saturn's rings are mostly ice, while Jupiter's are made of dust. Jupiter has three major rings. The Main Ring is very narrow and thin. The Halo Ring is closer to Jupiter than the Main Ring, and is a larger, diffuse cloud of particles. Outside the Main Ring is the wispy Gossamer Ring. It has two parts: Thebe Gossamer Ring (further out) and the Amalthea Gossamer Ring (closer in). Data from Galileo led scientists to discover the source of the ring material! The material in the rings is fine dust hurled up from the surfaces of Jupiter's inner moons by meteor impacts.

Although it is nearly invisible, the dust of Jupiter's rings fills much of the space near the giant planet. There are other, even less visible, features near Jupiter that Galileo's instruments helped us detect. The space near Jupiter is seething with powerful magnetic fields, intense storms of radiation, and swarms of energetic particles.

There are three types of data shown in the animation: radiation, energy, and electron density. The radiation values represent the general background radiation levels, and are expressed in units of counts. This type of radiation is caused by bombardment by electrons. The energy values are measurements from an instrument designed to register counts per second of sulfur ions in a certain energy range. Sulfur from Io's atmosphere "leaks out" into the space around Jupiter. The sulfur in Io's atmosphere comes from eruptions of Io's many volcanoes. Scientists are uncertain whether the instrument for measuring sulfur ion counts worked correctly. It may have been "swamped" by electrons, and given false readings. That instrument, called the Energetic Particle Detector, also measured counts of many other types of ions in various different energy ranges. The third value shown is electron density. It is expressed in terms of electrons per cubic centimeter. There are a lot of electrons zooming around the space near Jupiter!

If you want to learn more of the details about these values, check out the text in the "Advanced" version of this page.

Last modified October 7, 2003 by Randy Russell.

You might also be interested in:

Cool It! Game

Check out our online store - minerals, fossils, books, activities, jewelry, and household items!...more

Galileo

The Galileo spacecraft was launched on October 19, 1989. Galileo had two parts: an orbiter and a descent probe that parachuted into Jupiter's atmosphere. Galileo's main mission was to explore Jupiter and...more

Europa

Europa was first discovered by Galileo in 1610, making it one of the Galilean Satellites. It is Jupiter's 4th largest moon, 670,900 km from Jupiter. With a diameter that is about half the distance across...more

Adrastea

Adrastea is a small moon of Jupiter. Of Jupiter's 60 moons, it is the second closest to the planet. Adrastea was discovered by David Jewitt and Ed Danielson of the Voyager team in 1979. Adrastea is tiny...more

Amalthea

Amalthea was discovered by E Barnard in 1872. Of the 17 moons it is the 3rd closest to Jupiter, with a standoff distance of 181,300 km. Amalthea is about the size of a county or small state, and is just...more

The Rings of Jupiter

Jupiter has a series of rings circling it! Unlike Saturn's rings, which are clearly visible from Earth even through small telescopes, Jupiter's rings are very difficult to see. So difficult, in fact, that...more

Saturn's Rings

Many people like Saturn's rings. Although Saturn isn't the only planet with rings, it is the only planet famous for them. Almost every image or drawing of the planet has the rings included. But few people...more

Galileo Discovers Origin of Jupiter's Rings

Scientists recently discovered the origin of Jupiter's rings. With the help of the Galileo spacecraft, scientists figured out that the rings are made from dust that was kicked off of the small moons surrounding...more

Windows to the Universe, a project of the National Earth Science Teachers Association, is sponsored in part is sponsored in part through grants from federal agencies (NASA and NOAA), and partnerships with affiliated organizations, including the American Geophysical Union, the Howard Hughes Medical Institute, the Earth System Information Partnership, the American Meteorological Society, the National Center for Science Education, and TERC. The American Geophysical Union and the American Geosciences Institute are Windows to the Universe Founding Partners. NESTA welcomes new Institutional Affiliates in support of our ongoing programs, as well as collaborations on new projects. Contact NESTA for more information. NASA ESIP NCSE HHMI AGU AGI AMS NOAA