Xenoliths in maars and diatremes with inferences for the moon, Mars, and Venus.

Some field observations of the occurrence of deep-seated rock fragments in three terrestrial volcanic features that may have counterparts on the moon or Mars are reviewed, and results of numerical hydrodynamic calculations of the eruption of these types of volcanoes are presented. In particular, the transport of entrained fragmental debris is investigated for the surface (muzzle) velocity of fragments that it yields as a function of fragment size and various values of surface gravity. The implications of these observations and inferences for possible future space missions are examined.