Early aqueous alteration, explosive disruption, and reprocessing of asteroids

Several classes of chondritic meteorites experienced heterogeneous aqueous alteration and subsequent brecciation before agglomeration into the final p arent bodies. These processes resulted in intimate mixing of materials alte red to various degrees. In the past, this mixing has been attributed solely to impact processes. However, our investigation of the physical consequenc es of aqueous alteration processes in bodies accreting from a mixture of si licate and ice grains shows that aqueous alteration was commonly accompanie d by substantial gas production. The asteroids may have become so internall y pressurized by these gases that the sudden onset of gas release led to pa rtial or complete disaggregation of the body. In some cases, fragments may have escaped completely from the parent asteroid and could potentially have been incorporated into other accreting asteroids. In other cases, fragment s originating from different parts of the initial body, having various size s and temperatures and exhibiting varying degrees of alteration, may have r e-accreted into a second-generation object and undergone further stages of alteration. Such events could have been repeated two or three times during the lifetime of Al-26, th, likely heat source for these processes.