Guided Exploration: Building Planets
Overview: As the solar system was forming, countless small objects smashed into each other, gradually forming larger and larger bodies such as asteroids and planets. The meteorites in this section illustrate this process of accretion. Relatively rare, they are important in understanding the formation of planets, including Earth.
1. Crust, Mantle, Core, and Iron Crystals
As a planet forms, it melts and differentiates into layers. (The densest materials, like iron, sink to the center, while the lightest, like stones, float to the surface.) We can’t go deep inside planets, even our own, so meteorites from objects that were broken up after differentiation help us understand the process. Compare the specimens in the Crust, Mantle, and Core cases to understand the relationship between how meteorites look and where they originated. Next, examine meteorites in the Iron Crystals case that display the characteristic criss-crossing known as the Widmanstatten pattern. Explore how this pattern forms, and how scientists know that it’s found only in meteorites.
View specimens from Vesta, an asteroid that “lives” in the asteroid belt. What does comparing the three types of HED meteorites tell us about the processes that shaped Vesta?
Scientists figured out these meteorites came from a large planet that had water and volcanic activity. Mars fit the bill. But it wasn’t until NASA’s Viking probes landed in the 1970s and measured the composition of the Martian atmosphere that we had conclusive evidence: gases trapped inside these rocks were a perfect match. Explore these samples and the evidence they contain.