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Today in History: Galileo images of Ida reveal first asteroid moon

8/28/2026

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Summary

Story summary

On 28 August 1993 NASA’s Galileo probe, en route to Jupiter, performed a close flyby of asteroid 243 Ida. Images captured revealed a natural satellite—the first moon ever found orbiting an asteroid—making Ida the second asteroid visited by a spacecraft and the first known to host a moon.

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Story summary

On 28 August 1993 NASA’s Galileo probe, en route to Jupiter, performed a close flyby of asteroid 243 Ida. Images captured revealed a natural satellite—the first moon ever found orbiting an asteroid—making Ida the second asteroid visited by a spacecraft and the first known to host a moon.