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NASA’s space probe called “Juno” is now passing by Ganymede, the largest Moon in the solar system soon, in the closest flyby in two decades of any spacecraft near the heavenly body named after the handsome son of King Tros, whom Jupiter transported to heaven …

Ganymede, the largest moon in the solar system, is now the subject of a NASA fly-by. Credit: NASA/JPL-Caltech/SwRL/MSSS – NASA – Juno Space Craft (using junocam)/Public Domain
NASAs space probe called “Juno” is now passing by Ganymede, the largest Moon in the solar system soon, in the closest flyby in two decades of any spacecraft near the heavenly body named after the handsome son of King Tros, whom Jupiter transported to heaven on his back.
Jupiter’s largest satellite is the largest moon in the entire solar system — even larger than the planet Mercury. 
The ninth-largest object in our entire solar system, Ganymede is the largest to not have a substantial atmosphere of its own. It has a diameter of 5,268 km (3,273 miles), making it 26% larger than the planet Mercury itself.
The lighter-colored regions of ridges and grooves on Ganymede overlap darker-colored terrain forming the icy shell of the moon, which is highly metallic in its geological makeup. The scar-like areas suggest to astronomers that its surface experienced violent geologic changes over time.
Ganymede mission will help astronomers understand moon’s composition, icy exterior
Ganymede is the only one of Jupiter’s moons that was named after a male figure from Greek mythology; it circles the planet every seven days, along with the smaller moons named Io, Europa and Callisto.
NASA’s Juno space probe is zoom by Jupiter’s largest moon Ganymede this week, collecting new data about it for the very first time in two decades. The spacecraft, which has been going around Jupiter in an orbital pattern for the last five years, will fly by and do its research 645 miles above Ganymede’s surface at a speed of 43,200 miles per hour, according to a report from Smithsonian Magazine.
The new research will give astronomers a better understanding of Ganymede’s crust, which is made up of ice, as well as its magnetic field, as a way to help prepare for future missions to Jupiter, National Public Radio reports.
Scott Bolton, Juno’s principal investigator at the Southwest Research Institute in San Antonio, Texas, said in a statement “Juno carries a suite of sensitive instruments capable of seeing Ganymede in ways never before possible.
“By flying so close, we will bring the exploration of Ganymede into the 21st century, both complementing future missions with our unique sensors and helping prepare for the next generation of missions to the Jovian system.”
The gigantic moon is the only such body in our solar system with its own magnetic field, according to a report from The Verge. Its iron core produces the magnetic field, which is responsible for creating visible ribbons of glowing auroras enveloping both its north and south poles.
Over the spherical shell of iron-rich rock, Ganymede is covered by a 497-mile-thick ice shell that makes up the moon’s visible surface.
The Hubble Space Telescope was the first space probe to discover evidence of a thin layer of oxygen-rich atmosphere trapped in Ganymede’s icy surface back in 1996. Although this atmosphere is much too thin to support life as we know it, astronomers speculate that at one time there could have been conditions that were conducive to life on Ganymede and other such satellites.
Juno’s current flyby is the closest any spacecraft has been to the frozen moon of Jupiter since the “Galileo” probe flew by Ganymede back in the year 2000.
Before that time, NASA’s dual “Voyager” probes had observed the moon years earlier, in 1979. “Pioneer 10,” launched on March 2, 1972, was the first spacecraft to pass through the asteroid belt and the first to make direct observations and obtain close-up images of Jupiter.
A report in Space.com says that the new probe has several instruments designed to take even more spectacular photographs of Ganymede and gather more data on how it is composed. Its state-of-the-art technology include three different cameras, an array of radio instruments, an ultraviolet spectrograph, a microwave radiometer, and the “Jovian Infrared Auroral Mapper.”
The new NASA probe will begin collecting its scientific data fully three hours before it even arrives at its closest approach to Ganymede.
CNN reports that there’s even some intriguing evidence that an ocean may lie beneath Ganymede’s icy exterior. Scientists will employ NASA’s microwave radiometer to identify what the lighter and darker patches on the moon consist of as well as how the moon maintains its frozen shell.
Southwest Research’s Bolton said in a statement “Ganymede’s ice shell has some light and dark regions, suggesting that some areas may be pure ice while other areas contain dirty ice.
“(The microwave radiometer) will provide the first in-depth investigation of how the composition and structure of the ice varies with depth, leading to a better understanding of how the ice shell forms and the ongoing processes that resurface the ice over time.”
NASA’s JunoCam, which has already taken magnificent images of Ganymede, is also responsible for taking the new photos of the largest moon of Jupiter. In the space of only 25 minutes it has already snapped five different pictures of the satellite as it raced by.
The new photos will be compared to the earlier Voyage and Galileo images to spot any differences in the striations and any other discernable marks on its surface.
Naturally, the gigantic planet of Jupiter — the largest in the solar system — will receive its due as part of the mission, as Juno will provide information to other Jovian missions, including the Europa Clipper, sponsored by NASA, as well as the European Space Agency’s upcoming Jupiter Icy moons Explorer (JUICE) mission.
Both of these efforts will focus on a search for life on the icy bodies and make detailed observations of their surfaces, according to CNN.
The Italian astronomer Galileo Galilei was the first to observe what he thought were three stars near Jupiter, on January 7, 1610.
The “stars” turned out to be Ganymede, Callisto, another body that turned out to be the combined light from the smaller moons of Io and Europa; on the next night he noticed that they had moved.
On January 13, Galileo observed all four bodies at once for the first time. By January 15, the brilliant astronomer came to the conclusion that the “stars” were actually some kind of heavenly bodies in orbit around Jupiter.
Its name was soon suggested by astronomer Simon Marius, after the mythological Ganymede, a Trojan prince desired by Zeus (the Greek counterpart of the Roman god Jupiter), who carried him off to be the cupbearer of the gods.
“Then there was Ganymede, the handsome son of King Tros, whom Jupiter, having taken the form of an eagle, transported to heaven on his back, as poets fabulously tell… The Third (moon) is called Ganymede by me on account of its majesty of light… Io, Europa, the boy Ganymede, and Callisto greatly pleased lustful Zeus.”