Asteroid Gaspra's Best Face . ... 12.07.1998 . ... Credit Copyright: The Galileo Project , NASA Explanation: Asteroid 951 Gaspra is a huge rock tumbling in space. Gaspra became one of the best-studied asteroids in 1991 when the spacecraft Galileo flew by. ... Gaspra is about 20 kilometers long and orbits the Sun in the main asteroid belt between Mars and Jupiter . ... NASA Web Site Statements, Warnings, and Disclaimers . NASA Official: Jay Norris. ... A service of: LHEA at NASA / GSFC . ...