NASA’s Juno mission took pictures as it rocked 1,038 kilometers from Ganymede’s surface in flight, the closest spacecraft to the moon since the Galileo spacecraft made its approach in May 2000.
“This is the closest any spacecraft to this mammoth moon of a generation,” said Juno chief researcher Scott Bolton of the Southwest Research Institute in San Antonio, Texas.
“We’ll take some time before we can draw any scientific conclusions, but until then we can just marvel at this heavenly wonder.”
At 3,270 miles in diameter (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 the cupbearer of the ancient Greek gods. As well as being the largest natural satellite in our solar system, Ganymede is the only moon with a magnetic field. This makes the northern lights shine around the north and south poles of the moon.
Ganymede has an iron core covered with a layer of rock that is covered with a thick ice shell. There may be an underground ocean, and astronomers found evidence of a thin oxygen atmosphere on the moon in 1996 using the Hubble Space Telescope. This atmosphere is too thin to sustain life.
The dark side of Ganymede
Using its green filter, the spacecraft’s JunoCam visible light camera captured almost the entire side of the moon, which is inlaid with water ice, NASA said.
NASA said it hoped to provide a “color portrait” later when there were versions of the same image taken with the camera’s red and blue filters.
In addition, Juno’s star reference block, a navigation camera that keeps the spacecraft in motion, captures a black-and-white image of Ganymede’s dark side (the side opposite the sun).
“The conditions under which we collected Ganymede’s dark side image were ideal for a low-light camera like our star reference unit,” said Heidi Becker, head of Juno’s radiation monitoring laboratory at NASA’s Jet Propulsion Laboratory. “So it’s a different part of the surface than seen by JunoCam in direct sunlight. It’ll be fun to see what the two teams can combine.”
The solar-powered spacecraft’s encounter with the moon is expected to shed light on its composition, its magnetic field and ice sheet.