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On this day in space! Oct. 29, 1991: NASA's Galileo spacecraft flies by asteroid Gaspra and snaps amazing photos whil...
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On Oct. 29, 1991, NASA's Galileo spacecraft flew past asteroid Gaspra at about 18,000 mph. It passed within 990 miles (1,593 kilometers) and captured the first close-up images of an asteroid. The encounter was the first spacecraft visit to an asteroid.
NASA launched Galileo toward Jupiter in October 1989. The probe swung by Venus and Earth in 1990 before entering the asteroid belt and traveling about two months to Gaspra. The asteroid orbits near the inner edge of the main belt.
Galileo used cameras and a Near-Infrared Mapping Spectrometer to study Gaspra's shape and composition. Images showed an irregular, elongated, cratered body about 12 miles long and 7 miles wide. NASA described it as roughly 20 by 12 by 11 kilometers, covered by thin dust and rubble.
The flyby was a scientific pit stop near the midpoint of Galileo's six-year journey. Galileo later flew by Earth in 1992, asteroid Ida in 1993, and reached Jupiter in 1995. In July 1994, it observed Comet Shoemaker-Levy 9 crashing into Jupiter.
Galileo imaging team member Joseph Veverka said the picture showed something that "suffered a lot during its history." He suspected Gaspra was "the survivor of a series of catastrophic collisions in the past." The flyby demonstrated that asteroids could be studied closely by passing spacecraft.
Since then, NASA and other agencies have landed on asteroids, returned samples, and intentionally crashed probes into them. NEAR landed on Eros, OSIRIS-REx and Japan's Hayabusa missions returned samples, and DART tested planetary protection. Gaspra remains a milestone that opened asteroid exploration.
