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Why is a meteorite crater much wider than the object that made it?

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four impact craters — Meteorite crater Four impact craters of the same size (30 km [20 miles] in diameter) imaged by spacecraft on different solid bodies of the solar system and reproduced at the same scale. They are (clockwise from upper left) Golubkhina crater on Venus, Kepler crater on the Moon, an unnamed crater on Jupiter's moon Ganymede, and an unnamed crater on Mars. The images are oriented such that the craters appear illuminated from the left; the Venusian crater is imaged in radar wavelengths, the others in visible light.

A meteorite crater is significantly wider than the object that created it because the formation process is a hypervelocity impact, which functions more like an atomic bomb explosion than a simple mechanical indentation.1

When a meteorite strikes a planetary surface at speeds of several tens of kilometers per second, it releases an enormous amount of kinetic energy in a very small area over a short duration. This energy creates intense shock waves that propagate into the surface, vaporizing the meteorite and melting or crushing the surrounding rock.12

The resulting pressure gradients generate a subsurface flow that projects material upward and outward, excavating a cavity far larger than the original projectile. While the specific ratio depends on various factors, the diameter of the resulting crater is typically about 10 times that of the impacting object.1