📖 About Vesta

Vesta is the second-largest object in the asteroid belt after Ceres, with a mean diameter of 525 km. Unlike most asteroids, Vesta is a differentiated body—it has an iron core, a rocky mantle, and a basaltic crust, making it essentially a protoplanet that never completed its formation into a full planet. Vesta is so bright that it is occasionally visible to the naked eye, the only asteroid for which this is true.

The most dramatic feature on Vesta is the Rheasilvia impact basin at the south pole, spanning 505 km across—nearly the entire diameter of the asteroid. This colossal impact, which occurred about 1 billion years ago, excavated approximately 1% of Vesta’s volume and sent debris throughout the solar system. Many of the HED (Howardite-Eucrite-Diogenite) meteorites found on Earth originated from this impact, giving us actual pieces of Vesta to study in laboratories.

NASA’s Dawn spacecraft orbited Vesta from July 2011 to September 2012, mapping the entire surface in detail before departing for Ceres. Dawn revealed a complex geological history including ancient lava flows, a system of enormous troughs (Divalia Fossae) encircling the equator, and the massive Rheasilvia basin with a central peak 22 km high—more than twice the height of Mount Everest. Vesta provides crucial evidence about the earliest stages of planetary formation.

🔭 Key Features

🔬 Science & Future

Vesta is invaluable for understanding how rocky planets like Earth began forming. As a surviving protoplanet, it preserves the earliest stages of planetary differentiation—when heat from radioactive decay melted the interior, causing heavy iron to sink and light rock to rise. The HED meteorites allow scientists to study Vesta’s composition with laboratory precision, bridging remote observations with ground truth.

Comparing Vesta and Ceres—both visited by Dawn—reveals how different conditions in the asteroid belt led to very different outcomes. While Ceres retained significant water and never fully differentiated, Vesta became dry and rocky with a clearly layered interior. Future sample return missions could provide even more detailed information about Vesta’s history and the building blocks of the terrestrial planets.

📜 Discovery & Exploration

Heinrich Wilhelm Olbers discovered Vesta on March 29, 1807—the fourth asteroid found after Ceres, Pallas, and Juno. Named after the Roman goddess of home and hearth, Vesta was initially classified as a planet before being reclassified as an asteroid. It is the brightest asteroid and the only one sometimes visible without a telescope.

NASA’s Dawn spacecraft entered Vesta orbit on July 16, 2011, beginning a 14-month investigation. Using a framing camera, visible and infrared spectrometer, and gamma ray/neutron detector, Dawn mapped the surface at resolutions down to 20 meters per pixel. The mission revealed that Vesta is more planet-like than asteroid-like, fundamentally changing our understanding of these small worlds.