When a cosmic impact strikes the sea bed

Most bolides that collide with the Earth hit the sea. Limited knowledge abo ut marine-target impacts hampers predictions about their perilousness. This study presents geological features that are particular to craters formed a t sea. The features are most likely a result of the influence of the target on the cratering process. Marine-target craters form only if the target se a is shallow enough to admit sufficient kinetic energy into the sea bed. Wh en the crater diameter is large compared to the water depth, the crater res embles its counterparts that are formed on land. Craters formed in deeper w ater are concentric, and often lack melt sheets and rim walls, but have dep osits and radial gullies formed by the resurge of the sea. Impacts on the d eep shelf are probably much more energetic than is suggested by the dimensi ons of the preserved crater.