- Pallas is the third-largest object in the asteroid belt and the second asteroid ever discovered, identified in 1802 by German astronomer Heinrich Wilhelm Olbers, just one year after the discovery of Ceres.
- With an average diameter of about 512 kilometers (318 miles), Pallas accounts for roughly 7% of the asteroid belt’s total mass. Despite its size and early discovery, Pallas remains relatively understudied compared to Ceres and Vesta, largely due to its highly inclined and eccentric orbit, which makes close spacecraft encounters more challenging. Its orbit is tilted at about 34.8 degrees relative to the plane of the solar system—a feature that distinguishes it from most large asteroids and may reflect a dynamic and possibly violent early history.
- Pallas is classified as a B-type asteroid, a subclass of carbonaceous asteroids. This type is rich in volatile compounds and primitive materials believed to be among the oldest in the solar system. Its dark surface suggests the presence of carbonaceous material and possibly hydrated silicates, indicating that Pallas may have undergone some degree of aqueous alteration. Unlike Vesta, which experienced extensive internal differentiation and volcanic activity, Pallas appears to have preserved much of its primordial composition, making it a valuable object for studying the solar system’s earliest solid material.
- The surface of Pallas is heavily cratered, suggesting an ancient and relatively unchanged crust. Observations from Earth-based telescopes and the Hubble Space Telescope have revealed large impact features, but details of its topography remain limited. In recent years, the European Southern Observatory’s Very Large Telescope and adaptive optics imaging have begun to shed more light on Pallas’s shape and surface features, revealing an oblate, somewhat irregular form with evidence of massive craters that point to a history of high-energy collisions.
- Pallas is considered a protoplanet—an early planetary building block that never fully developed into a planet. Its combination of size, carbon-rich composition, and orbital uniqueness makes it an important target for understanding the distribution of water and organic materials in the early solar system. While no spacecraft has visited Pallas to date, its scientific value remains high, and it is considered a candidate for future exploration missions. As a relic from the dawn of planetary formation, Pallas holds important clues about the conditions that gave rise to the planets and possibly to the origins of life-supporting molecules on Earth.
