NASA’s Juno mission took the pictures as it orbited within 1,038 kilometers from Ganymede’s surface during an airplane, the closest a spacecraft has been to the moon since the Galileo spacecraft made its approach in May 2000.
“This is the closest a spacecraft has come to this mammoth moon in a generation,” said Juno Principal Investigator Scott Bolton of the Southwest Research Institute in San Antonio, Texas.
“We will take our time before we draw any scientific conclusions, but until then we can simply marvel at this heavenly wonder.”
At 5,270.4 kilometers (5,262.4 kilometers), this giant moon is larger than the planet Mercury.
The images ̵
The spacecraft has been observing Jupiter and its moons since July 2016.
The moon is named after a bowl bearer of the ancient Greek gods. Besides being the largest natural satellite in our solar system, Ganymede is also the only moon to have a magnetic field. This causes the northern lights to glow around the moon’s north and south poles.
Ganymede has an iron core covered by a layer of rock topped with a thick ice shell. It is possible that there is an ocean underground, and astronomers discovered signs of a thin oxygen atmosphere on the moon in 1996 using the Hubble Space Telescope. This atmosphere is too thin to support life.
Dark side of Ganymede
Using its green filter, the spacecraft’s JunoCam camera with visible light captured almost an entire side of the moon, which is trapped in water ice, NASA said.
NASA said it later hoped to provide a “color portrait” when it has versions of the same image taken with the camera’s red and blue filters.
In addition, Juno’s Stellar Reference Unit, a navigation camera that keeps the spacecraft on course, snapped a black-and-white image of Ganymede’s dark side (side opposite the sun).
“The conditions under which we assembled the dark side image of Ganymede were ideal for a low-light camera like our Stellar Reference Unit,” said Heidi Becker, Juno’s radiation monitoring line at NASA Jet Propulsion Laboratory. “So this is a different part of the surface than seen by JunoCam in direct sunlight. It will be fun to see what the two teams can put together.”
The solar-powered spacecraft’s encounter with the moon is expected to shed light on its composition, its magnetic field and its icy shell.