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Today in History: Galileo discovers first asteroid moon around Ida

8/28/2026

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Summary

Story summary

On 28 August 1993, NASA’s Galileo probe, en route to Jupiter, executed a close flyby of asteroid 243 Ida. Images taken during the encounter revealed Dactyl, the first natural satellite discovered orbiting an asteroid, proving that minor planets can host moons and enabling new mass-density investigations.

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Story summary

On 28 August 1993, NASA’s Galileo probe, en route to Jupiter, executed a close flyby of asteroid 243 Ida. Images taken during the encounter revealed Dactyl, the first natural satellite discovered orbiting an asteroid, proving that minor planets can host moons and enabling new mass-density investigations.