A comet’s potential for destruction is defined by its mass and speed.
What Is a Comet? | NASA Space Place – NASA Science for Kids Comet Impact
: Upon impact, comets can create massive vapor plumes that rise thousands of kilometers into the atmosphere, depositing debris that increases opacity and drastically lowers global temperatures. Historical and Theoretical Impacts A comet’s potential for destruction is defined by
: While asteroids typically hit at about 20 km/s, comets can reach speeds up to 71 km/s. Because kinetic energy scales with the square of velocity, a comet can deliver more than 100 times the energy of a similarly sized asteroid. Comet Impact
: Long-period comets can be pulled apart by the sun's gravity before reaching Earth, potentially hitting as a "cluster" of fragments rather than a single body.