Animation of a rotating globe of Jupiter's moon
Ganymede, with a geologic map superimposed over a global color mosaic. The
37-second animation begins as a global color mosaic image of the moon then
quickly fades in the geologic map.
Image Credit:
USGS Astrogeology Science
Ctr/Wheaton/ASU/NASA/JPL-Caltech
Feature Link:
To present the best information in a single view of
Jupiter's moon Ganymede, a global image mosaic was assembled, incorporating the
best available imagery from NASA's Voyager 1 and 2 spacecraft and NASA's Galileo
spacecraft.
Image Credit:
USGS Astrogeology Science
Center/Wheaton/NASA/JPL-Caltech
Feature Link:
More than 400 years after its discovery by astronomer Galileo Galilei, the
largest moon in the solar system – Jupiter's moon Ganymede – has finally claimed
a spot on the map.
A group of scientists led by Geoffrey Collins of Wheaton College has produced
the first global geologic map of Ganymede, Jupiter’s seventh moon. The map
combines the best images obtained during flybys conducted by NASA's Voyager 1
and 2 spacecraft (1979) and Galileo orbiter (1995 to 2003) and is now published
by the U. S. Geological Survey as a global map. It technically illustrates the
varied geologic character of Ganymede’s surface and is the first global,
geologic map of this icy, outer-planet moon.
“This map illustrates the incredible variety of geological features on
Ganymede and helps to make order from the apparent chaos of its complex
surface,” said Robert Pappalardo of NASA’s Jet Propulsion Laboratory in
Pasadena, Calif. “This map is helping planetary scientists to decipher the
evolution of this icy world and will aid in upcoming spacecraft
observations.”
The European Space Agency's Jupiter Icy Moons Explorer mission is slated to
be orbiting Ganymede around 2032. NASA is contributing a U.S.-led instrument and
hardware for two European-led instruments for the mission.
Since its discovery in January 1610, Ganymede has been the focus of repeated
observation, first by Earth-based telescopes, and later by the flyby missions
and spacecraft orbiting Jupiter. These studies depict a complex, icy world whose
surface is characterized by the striking contrast between its two major terrain
types: the dark, very old, highly cratered regions, and the lighter, somewhat
younger (but still very old) regions marked with an extensive array of grooves
and ridges.
According to the scientists who have constructed this map, three major
geologic periods have been identified for Ganymede that involve the dominance of
impact cratering, then tectonic upheaval, followed by a decline in geologic
activity. The map, which illustrates surface features, such as furrows, grooves
and impact craters, allows scientists to decipher distinct geologic time periods
for an object in the outer solar system for the first time.
“The highly detailed, colorful map confirmed a number of outstanding
scientific hypotheses regarding Ganymede’s geologic history, and also disproved
others,” said Baerbel Lucchitta, scientist emeritus at the U.S. Geological
Survey in Flagstaff, Ariz., who has been involved with geologic mapping of
Ganymede since 1980. “For example, the more detailed Galileo images showed that
cryovolcanism, or the creation of volcanoes that erupt water and ice, is very
rare on Ganymede.”
The Ganymede global geologic map will enable researchers to compare the
geologic characters of other icy satellite moons, because almost any type of
feature that is found on other icy satellites has a similar feature somewhere on
Ganymede.
“The surface of Ganymede is more than half as large as all the land area on
Earth, so there is a wide diversity of locations to choose from,” Collins said.
“Ganymede also shows features that are ancient alongside much more
recently formed features, adding historical diversity in addition to geographic
diversity.”
Amateur astronomers can observe Ganymede (with binoculars) in the evening sky
this month, as Jupiter is in opposition and easily visible.
The project was funded by NASA through its Outer Planets Research and
Planetary Geology and Geophysics Programs. NASA's Jet Propulsion Laboratory is
managed by the California Institute of Technology,
Pasadena.
NASA
Guillermo Gonzalo Sánchez Achutegui
