Shop Windows to the Universe

Please help support Windows to the Universe, and our activities to help Earth and space science teachers, with a tax-exempt donation today!

Ganymede's Atmosphere

The Galileo mission discovered that Ganymede not only has a magnetosphere, but its own atmosphere as well, although it is very, very thin. The atmosphere is created when molecules from the magnetosphere, moving very fast, hit the surface and knock out a water molecule. Because there is a magnetosphere, the atmosphere of Ganymede does not simply ‘float away’ like the atmosphere of Europa does.

One of the instruments on the spacecraft measured a stream of hydrogen molecules flowing away from the moon over its north pole. Another instrument measured the presence of an Ionosphere, a part of the atmosphere that is filled with ions. If molecules are leaving Ganymede all the time, that means they have to be replaced all the time, and that means there must be an active process that is creating the atmosphere. This image from the Hubble Space Telescope shows ozone on Ganymede. Ozone is an important constituent of the Earth’s atmosphere.

Even though Ganymede and Callisto have thin atmospheres, there does not seem to be a Ganymede or Callisto torus, the way there is at Europa and Io.

Last modified September 19, 2003 by Jennifer Bergman.

Shop Windows to the Universe Science Store!

Our online store includes books on science education, classroom activities in The Earth Scientist, mineral and fossil specimens, and educational games!

Windows to the Universe Community

News

Opportunities

You might also be interested in:

Cool It! Game

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

Magnetosphere of Ganymede

When the Galileo spacecraft flew by Ganymede, it found something that was a big surprise to everyone -- a very strong magnetic field. This is the first time a strong magnetic field had been found near...more

The Atmosphere of Europa

The Galileo mission discovered something amazing! 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...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

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

Galileo Reaches the End of its Road

The Galileo spacecraft has finally reached the end of its road. Galileo has been orbiting Jupiter since 1995. On September 21, 2003, Galileo will dive into Jupiter's atmosphere and burn up. This crash...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

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

Windows to the Universe, a project of the National Earth Science Teachers Association, is sponsored in part by the National Science Foundation and NASA, our Founding Partners (the American Geophysical Union and American Geosciences Institute) as well as through Institutional, Contributing, and Affiliate Partners, individual memberships and generous donors. Thank you for your support! NASA AGU AGI NSF