Atmospheric collection of debris from the Revelstoke and Allende fireballs

In two separate events, Revelstoke and Allende, the air through which a fireball had been observed to pass was sampled for meteoritic debris. Particulate matter was collected on fibrous filters, which were mounted on aircraft and flown downwind from the site of the meteorite fall at altitudes of 10,000–12,000 m. From Revelstoke, a highly distinctive assemblage of particles was collected. Included were large numbers of magnetite spherules, transparent siliceous spherules, and several types of irregular nickel-bearing particles. The Allende collections yielded only slightly more magnetite and siliceous spherules than background and no nickel-bearing particles. Revelstoke and Allende are believed to be representative of two different types of events. In the Revelstoke type, large amounts of meteoritic debris are left in the atmosphere and little reaches the ground in large coherent fragments; in the Allende type, little material remains in the atmosphere but large fragments reach the ground in the fall area.