How Asteroids Help Us Understand the Formation of the Solar System
An artist’s impression of the one of two asteroid belts in the Epsilon Eridani solar system some 10.5 light years from Earth. With the right gravitational conditions, an asteroid belt such as this can form a protoplanetary disk that may eventually lead to the formation of rocky terrestrial planets.
Owing to their incredibly diverse nature, it’s not easy to define asteroids based on composition alone. Some are made largely of iron and nickel, while others, such as Ceres, appear to consist of a rocky core covered by vast amounts of water ice. More precisely what asteroids are made of remains shrouded in mystery, with most of what we know being down to educated guesswork based on observations of the reflectivity (albedo) of their surfaces.
Some 4.6-billion years ago, our solar system consisted of a chaotic primordial soup in the form of a protoplanetary disk rotating around a young star. Heavier elements, such as iron, came together to form the first meteoroids, asteroids and comets. Areas with higher concentrations of these fundamental building blocks saw much larger amounts of material came together, bound by gravity, to form the terrestrial planets such as Earth.
Asteroids represent the left-over building blocks from the formation of the planets. However, since those far-off times, they have diversified enormously, owing to countless collision events over the aeons. Vesta, the second-most massive asteroid, for example, may actually be the left-over core of a failed protoplanet, as indicated by its crust of solidified lava. Ceres, on the other hand, may even have a subsurface ocean, indicating that asteroids, perhaps along with comets, could have brought water to the early Earth.