Answer:
What happens when an impactor hits?
When an impactor strikes the solid surface of a planet, a shock wave spreads out from the site of the impact. The shock wave fractures the rock and excavates a large cavity (much larger than the impactor). The impact sprays material — ejecta — out in all directions. The impactor is shattered into small pieces and may melt or vaporize. Sometimes the force of the impact is great enough to melt some of the local rock. If an impactor is large enough, some of the material pushed toward the edges of the crater will slump back toward the center and the rock beneath the crater will rebound, or push back up, creating a central peak in the crater. The edges of these larger craters also may slump, creating terraces that step down into the crater.
What are the major parts of a crater?
Floor – The bottom of a crater, either bowl-shaped or flat, usually below the level of the surrounding ground.
Central peaks – Peaks formed in the central area of the floor of a large crater. For larger craters (typically a few tens of kilometers in diameter) the excavated crater becomes so great that it collapses on itself. Collapse of the material back into the crater pushes up the mound that forms the central peak. At the same time, the rock beneath the crater rebounds, or bounces back up to add to the peak.
Walls – The interior sides of a crater, usually steep. They may have giant stair-like terraces that are created by slumping of the walls due to gravity.
Rim – The edge of the crater. It is elevated above the surrounding terrain because it is composed of material pushed up at the edge during excavation.
Ejecta – Rock material thrown out of the crater area during an impact event. It is distributed outward from the crater's rim onto the planet's surface as debris. It can be loose materials or a blanket of debris surrounding the crater, thinning at the outermost regions.
Rays – Bright streaks extending away from the crater sometimes for great distances, composed of ejecta material.
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