On October 29, 1991, just over two years after its launch, Galileo performed the first close flyby of an asteroid by a spacecraft. It came a mere 1,600 km (1, 000 miles) of the asteroid Gaspra.

Gaspra was first discovered by Grigoriy Neujamin in 1916. Gaspra is a small and irregular body roughly 20 x 12 x 11 km (12.5 x 7.5 x 7 miles) in size. Not much attention was given to it until it was discovered that the trajectory of the Galileo spacecraft would take it close to Gaspra. It then became a prime target for exploration.

At closest approach, Galileo passed Gaspra at 8 km (5 miles) per second!