Impact on rock, water, and air

It is argued that the meteorite-impact accretion is a process vital to the formation of the earth and terrestrial planets and that the evolution of the surfaces with time is affected by impacts. The paper reviews the previous calculations of Ahrens and O'Keefe of the effect of meteorite impacts on the rock surface of the earth, on the ocean, and the atmosphere, and presents some new work on the mechanism of impact-induced atmospheric escape. Using the similarity solution, the mass of atmosphere lost due to the impacts of 1 to 5 kg radius projectiles is calculated. It is shown that no atmosphere is lost for surface sources with energies less than 10 to the 27th erg. Impact of objects in the energy range 10 to the 27th to 10 to the 30th ergs causes gas losses of 10 to the 11th to 10 to the 14th kg (i.e., 10 to the -8th to 10 to the -5th of the total present atmospheric budget). Impact energies of greater than 10 to the 30th ergs cause little increase in atmospheric loss.