Gaspra (Asteroid 951) was discovered by Grigoriy N. Neujamin in 1916. Neujamin named Gaspra after a Black Sea retreat that was visited by contemporaries such as Tolstoy and Gorky. Gaspra was just another small asteroid that was given very little attention until it was discovered that the trajectory of the Galileo spacecraft would take it close to Gaspra. Following this discovery, observers through out the world made Gaspra a prime target of study. Gaspra was found to have an elongated shape with a rotational period of 7.04 hours.
On October 29, 1991, Galileo came within 1,600 kilometers (1,000 miles) of Gaspra. They passed each other at 8 kilometers (5 miles) per second. This was the first time that a spacecraft made a fly-by of an asteroid. Gaspra is an irregular body with dimensions of about 20 x 12 x 11 km (12.5 x 7.5 x 7 miles). Its surface reflects approximately 20 percent of the sunlight striking it. Gaspra is classified as an S-type asteroid and is likely composed of metal-rich silicates and perhaps blocks of pure metal. It is a member of the Flora family.
Several craters are visible on Gaspra, but none approach the scale of the asteroid's radius. The fact that Gaspra is irregular in shape and lacks any large craters suggests that it has a comparatively recent origin, most likely from the collisional breakup of a larger body. Gaspra has probably been in its present state for the last 300 to 500 million years.
MEAN RADIUS: 5x5.5x9 km MASS: ? (Earth=1) DENSITY: ? (gm/cm) GRAVITY: ? (Earth=1) ORBIT PERIOD: 3.28 (Earth years) ROTATION PERIOD: ? (Earth days) SEMIMAJOR AXIS OF ORBIT: 2.21 au (Earth=1) ECCENTRICITY OF ORBIT: 0.173 (Earth=0.017)