NASA’s Juno spacecraft recently captured intriguing images of Amalthea, Jupiter’s fifth moon, during its 59th close flyby of the gas giant. While Jupiter’s Galilean moons—Io, Europa, Ganymede, and Callisto—are well-known, Amalthea, discovered in 1892 by Edward Emerson Barnard, remains shrouded in mystery. According to NASA, Amalthea has a potato-like shape, lacking the mass to form a sphere, and is the reddest object in the solar system.
During its flyby on March 7, 2024, Juno provided researchers with a rare view of Amalthea as it transited Jupiter’s Great Red Spot. NASA’s blog detailed the event: “NASA’s Juno mission captured these views of Jupiter during its 59th close flyby of the giant planet on March 7, 2024. They provide a good look at Jupiter’s colorful belts and swirling storms, including the Great Red Spot. Close examination reveals something more: two glimpses of the tiny moon Amalthea.” The moon appeared as a small dot against Jupiter’s reddish, dark cloud bands.
In the released images, Amalthea was visible transiting the Great Red Spot, with Juno approximately 165,000 miles (265,000 kilometers) above Jupiter’s cloud tops at the time, at a latitude of about 5 degrees north of the equator. This rare sighting has reignited interest in the lesser-known moon.
Amalthea orbits within Io’s path, taking just 0.498 Earth days to complete one orbit around Jupiter. Despite its small size and irregular shape, Amalthea holds significant interest for scientists. It emits slightly more heat than it receives from the Sun, a phenomenon that has led to several theories. One suggests that Amalthea absorbs heat from Jupiter both directly and indirectly, while another proposes that tidal pressures within the moon, caused by Jupiter’s gravitational pull, generate additional heat.
Historically, Amalthea has been overshadowed by its larger siblings. The Galileo spacecraft, which previously visited Jupiter, revealed some of Amalthea’s surface features, including impact craters, hills, and valleys. However, detailed scientific discussions often omit this intriguing moon.
As Juno continues its mission, the new images and data from Amalthea offer scientists a fresh opportunity to study this enigmatic satellite and uncover more about its characteristics and its relationship with Jupiter.
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