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How are impact craters formed on planetary surfaces?

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continental landform Davis's proposed landscape-development states. The morphology shown is not actually time-indicative. For example, A could be a gully system in soft sediment or a canyon such as the Royal Gorge in Colorado, which is millions of years old. The ridge-ravine topography of B would normally develop under humid conditions, but the river meandering on alluvium indicates a prior or extraneous non-humid aggrading mechanism. The riverine plain of C implies a complex history of planation and aggradation in a current fluvial mode.

Impact craters are circular depressions formed on planetary surfaces primarily by the hypervelocity impact of asteroidal or cometary objects. Contrary to the simple analogy of a pebble hitting sand, these events are physically similar to atomic bomb explosions, releasing massive amounts of kinetic energy in a localized area.12

The process follows a specific sequence:
* Excavation: Upon impact, shock waves vaporize the meteorite and crush surface material. Subsequent rarefaction waves create pressure gradients that project material outward, forming a parabolic bowl surrounded by an ejecta blanket.1
* Simple Craters: Smaller impacts conclude with this excavation stage, resulting in a simple, bowl-shaped depression.1
* Modification: For larger impacts, the initial cavity is unstable and collapses. This stage creates complex features such as flat floors, central peaks, or inner rings caused by material rebounding toward the center, as well as faulting along the inner rims.1

While common on many bodies in the solar system, these features are less frequently observed on Earth due to atmosphere protection and erosion.2