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Scientists release first geologic map of Jupiter's moon Ganymede

Elizabeth Howell, News Writer
Feb 14, 2014, 8:00 UTC

Sen—The first global geologic map of Jupiter's moon Ganymede, the largest moon in the Solar System, has been released. The project was led by Geoffrey Collins of Wheaton College, and the map is published on the United States Geological Survey website.

This new map could provide areas of study for the European Space Agency's Jupiter Icy Moon Explorer (Juice) when it arrives in the moon's orbit in 2032, whilst NASA's Juno spacecraft is already en route to Jupiter and will arrive in 2016.

"This map illustrates the incredible variety of geological features on Ganymede and helps to make order from the apparent chaos of its complex surface," stated Robert Pappalardo of NASA’s Jet Propulsion Laboratory in California.

"This map is helping planetary scientists to decipher the evolution of this icy world and will aid in upcoming spacecraft observations."

Ganymede, the largest moon in our Solar System (it is in fact larger than Mercury), was discovered in 1610 by Galileo Galilei along with three other Jovian moons: Europa, Callisto and Io.

The Hubble Space Telescope detected a thin oxygen atmosphere around the planet in 1996, but it is too tenuous to support life.

As there is no mission at Jupiter right now, scientists combined data from three long-finished missions at the planet to compile the map: Voyagers 1 and 2, which passed by in 1979, and the orbiting Galileo spacecraft which was there between 1995 and 2003.

Putting images from these missions on one map has shown scientists a few new things, including the demarcation of three geologic periods: one that saw craters arising through meteor impacts, tectonic changes, and then geologic activity slowing down.

"The highly detailed, colorful map confirmed a number of outstanding scientific hypotheses regarding Ganymede's geologic history, and also disproved others," stated Baerbel Lucchitta, scientist emeritus at the U.S. Geological Survey in Arizona.

"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," added Lucchitta, who has been working on geological mapping of Ganymede since 1980.

Scientists added that the map of Ganymede will help in predicting features on other icy moons in the solar system, which include fellow Jovian moons Europa and Callisto as well as others such as Saturn's Mimas and Uranus' Miranda.

One area of Ganymede that could bear more study is its distinctive "grooved" features that can rise as high as 700 metres (2,000 feet) and run for thousands of kilometres across the surface. NASA states that the grooves likely arise due to water coming from below the surface.