Chondrule formation: Nebular gas confinement of impact splashes

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The formation of chondrules is one of the oldest unsolved mysteries in meteoritics. One of the theories states that they are formed as a result of collisions between planetesimals in which the impact melt forms small droplets which solidify to become chondrules. Some constraints from meteoritics suggest that the material reaccreted rather soon after these chondrules were formed. However, immediate gravitational re-accretion of impact splashes is hard if the collision happened at very high velocity. On the other hand, low velocity collisions can only produce impact melt if the planetesimals were already nearly fully molten by 26Al decay before impact. I propose to study the effect of the decelleration of the impact splash by the nebular gas, which can cause the impact splash to remain confined and form dense "bullets". The densities of these "bullets" likely remain above the Roche density, so that they will be gravitationally bound and form new planetesimals. Reaccretion can thus occur even for high-speed impacts. We have performed two pilot studies. This proposal is to perform the full study and test of this scenario.