This day in space! Aug. 28, 1993: Galileo spacecraft flies by asteroid Ida on the way to Jupiter only to find a tiny moon!

On Aug. 28, 1993, NASA’s Galileo spacecraft flew past the asteroid Ida on its way to Jupiter and made a landmark discovery: a tiny moon called Dactyl. Galileo was the first spacecraft to fly by an asteroid in the asteroid belt, and Ida was the second target it visited after Gaspra in 1991. During the encounter, Galileo passed at nearly 28,000 mph and came within about 1,500 miles (around 2,400 kilometers) of Ida’s surface. The flyby confirmed Dactyl as the first confirmed asteroid satellite, strengthening the idea that asteroids can have moons. Ida, an S-type asteroid, was discovered in 1884 by Johann Palisa.