Astronomy Picture of the Day

Discover the cosmos! Each day a different image or photograph of our fascinating universe is featured, along with a brief explanation written by a professional astronomer.

2023 October 23
Jupiter's moon Io is shown as photogaphred recently
by NASA's passing Juno spacecraft. The moon is nearly half-
lit by the distant Sun and shows a complex surface including
the colors yellow, orange, and dark brown. Near the top, the
plume of an active volcano can be seen.
Please see the explanation for more detailed information.

Moon Io from Spacecraft Juno
Image Credit: NASA, JPL-Caltech, SwRI, MSSS; Processing & Copyright: Ted Stryk & Fernando García Navarro

Explanation: There goes another one! Volcanoes on Jupiter's moon Io keep erupting. To investigate, NASA's robotic Juno spacecraft has begun a series of visits to this very strange moon. Io is about the size of Earth's moon, but because of gravitational flexing by Jupiter and other moons, Io's interior gets heated and its surface has become covered with volcanoes. The featured image is from last week's flyby, passing within 12,000 kilometers above the dangerously active world. The surface of Io is covered with sulfur and frozen sulfur dioxide, making it appear yellow, orange and brown. As hoped, Juno flew by just as a volcano was erupting -- with its faint plume visible near the top of the featured image. Studying Io's volcanoes and plumes helps humanity better understand how Jupiter's complex system of moons, rings, and auroras interact. Juno is scheduled to make two flybys of Io during the coming months that are almost 10 times closer: one in December and another in February 2024.

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Tomorrow's picture: unwinding galaxies

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