Transient atmosphere generated by large meteoroid impacts onto an atmosphereless cosmic body: gasdynamic and physical processes

Impact of a large meteoroid or a man-made projectile with an atmosphereless cosmic body (Moon, Mercury, asteroid and comet) produces a transient atmosphere. Several physical aspects in the early and late phases of the impact generated vapor plume evolution are considered numerically and analytically. Intensity of light flashes and velocities versus mass distribution function are determined. For a 10 kg mass of impacting meteoroid, the plume intensively interacts with the solar wind in the region with the size of several hundred kilometers. For a 350 kg man-made projectile of the Deep Impact Mission hitting the P9 Comet Temple 1 with the velocity of about 10 km/s the size of the disturbed zone is of the order of 10 4 km. The expulsion of the interplanetary magnetic field, formation of the collisionless shock wave structure associated with intense electrostatic turbulence, electron heating, and even production of X-rays lasting for several minutes are characteristic features of such impacts. These effects give the basis for new techniques of remote detection of meteoroid impacts.