Ganymede has a diameter of 5,268 km, about 8% larger than that of the planet Mercury and much larger than the dwarf planet Pluto itself. Discovered in 1610, it is the only moon in the solar system to have its own magnetosphere , causing it to have auroras in the regions around its north and south poles.
Now, NASA’s Juno probe has obtained the closest images of this moon, which is one of the four moons of Jupiter that Galileo Galilei discovered in 1610. The probe has come within 1,000 kilometers of Ganymede, the closest any spacecraft has ever been to this moon in more than two decades.
The images show the moon’s surface in great detail, including craters, bright dark terrain, and long structural features possibly related to tectonic faults.
“This is the closest a spacecraft has come to this gigantic moon in a generation,” Juno principal investigator Scott Bolton of the Southwest Research Institute in San Antonio said in a statement. “We are going to take our time before drawing scientific conclusions, but until then we can just be amazed at this celestial wonder: the only moon in our solar system larger than the planet Mercury.”
A color portrait of Ganymede
NASA experts will also soon create color images from Juno data using red and blue filters , which will provide a color portrait of the moon.
Since Ganymede has no atmosphere, the surface of its poles is constantly being bombarded by plasma from Jupiter’s magnetosphere, which has a dramatic effect on the moon’s ice. The ice sheet on the outside is very thick, perhaps 500 miles thick.
The Juno images will also be compared with those taken by the Galileo probe between 2005 and 2004, and by the Voyager probe in 1979, to see if there have been any changes during this time.
