Juno captures the reddest object in the solar system: Amalthea

NASA’s Juno spacecraft captured these views of the small red moon Amalthea and its parent planet during a flyby on March 7, 2024.

Amalthea, also known as Jupiter V, is Jupiter’s third moon in order of distance from the gas giant.

Discovered in 1892 by American astronomer Edward Emerson Barnard, the Moon is irregular and measures approximately 250 x 146 x 128 km (155 x 91 x 80 miles).

Amalthea orbits Jupiter at a distance of 181,400 km (112,717 miles) and takes 0.498 Earth days to complete one orbit.

Each time it orbits Jupiter, it rotates once on its axis, always keeping the same side facing the planet.

Amalthea is the reddest object in the solar system and appears to emit more heat from the Sun than it receives.

This is likely due to the fact that the moon’s core contains electrical currents as it orbits within Jupiter’s strong magnetic field.

Alternatively, the heat could be due to tidal forces.

These images from Juno show Jupiter’s small moon Amalthea. Image credit: NASA / JPL-Caltech / SwRI / MSSS / Gerald Eichstädt.

“Amalthea is potato-shaped and lacks the mass to pull it into a sphere,” the Juno scientists said.

“In 2000, NASA’s Galileo spacecraft revealed several surface features, including impact craters, hills, and valleys.”

“Amalthea orbits Jupiter inside the orbit of Io. Io is the innermost of Jupiter’s four large moons and takes 0.498 Earth days to orbit.”

“At the time the first of these two images was taken, Juno was approximately 265,000 kilometers above Jupiter’s clouds and at a latitude of approximately 5 degrees north of the equator,” the researchers added.

“Citizen scientist Gerald Eichstedt created these images using raw data from Juno’s JunoCam instrument and applied processing techniques that enhance the clarity of the images.”