Shop Windows to the Universe

Our Glaciers: Then and Now activity kit helps you see the changes taking place in glaciers around the world. See all our activity kits and classroom activities.
A schematic of the environment nearest Jupiter, showing magnetically trapped particles in a portion of Jupiter's extensive radiation belts in red, the neutral gas of the Io torus in green, and the neutral gas of the Europa torus in blue. The picture is derived from data taken by the Cassini spacecraft.
NASA

The Atmosphere of Europa

The Galileo mission discovered an amazing thing. Europa has its own atmosphere, although it is very, very thin. This atmosphere is created when fast moving molecules in Jupiter's magnetosphere hit the surface of Europa and knock out a water molecule. This process is known as "sputtering". The surface may also evaporate, or "sublimate" when the Sun is shining, the way a comet does. Because there is little gravity however, a small moon cannot hold onto an atmosphere for very long.

Water molecules lost from the surface are quickly separated into the constituents oxygen and hydrogen. These molecules can also be quickly ionized by ultraviolet radiation and charged particles in the vicinity. Thus Europa has a neutral atmosphere as well as an ionosphere. These molecules may float around Europa for awhile, but because of Europa's weak gravity, the "atmosphere" rapidly drifts away.

A neutral component of oxygen near Europa was detected by the Cassini spacecraft as it flew by Jupiter in the year 2000, and is illustrated in the drawing to the left. This suggests that the components of Europa's atmosphere that float away create a torus of material inside Jupiter's magnetosphere. This belt of material is called the "Europa torus". Io also has a torus. Even though Ganymede and Callisto also have thin atmospheres, they do not seem to produce torii in Jupiter's inner magnetosphere. This probably has something to do with the shape of Jupiter's magnetosphere.


Last modified September 18, 2003 by Roberta Johnson.

Shop Windows to the Universe Science Store!

Learn about Earth and space science, and have fun while doing it! The games section of our online store includes a climate change card game and the Traveling Nitrogen game!

Windows to the Universe Community

News

Opportunities

You might also be interested in:

Traveling Nitrogen Classroom Activity Kit

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 primary mission was to explore the Jovian...more

An Overview of Jupiter's Magnetosphere

Jupiter's magnetosphere is a unique object in the solar system. It is the biggest object in the entire solar system. Not only is it big enough to contain all of Jupiter's moons, but the sun itself could...more

Cassini

The Cassini probe began its journey to Saturn on October 15, 1997. It flew by Earth in August, 1999, before heading towards the distant planet. Cassini passed Jupiter in 2000 and then burned towards its...more

The Io Torus

A satellite which has an atmosphere, such as Jupiter's moon Io, and which also is inside a magnetosphere (unlike the Earth's moon), will leave a cloud of particles behind as it orbits the planet. This...more

Callisto

Callisto was first discovered by Galileo in 1610, making it one of the Galilean Satellites. Of the 60 moons it is the 8th closest to Jupiter, with a standoff distance of 1,070,000 km. It is the 2nd largest...more

Europa

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

Galileo Reaches the End of its Road

The Galileo spacecraft, which has been orbiting Jupiter since 1995, has finally reached the end of its road. On September 21, 2003, Galileo will make a fiery plunge into Jupiter's atmosphere and be vaporized....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