Studies of particles for extraterrestrial origin: 2. A comparison of microscopic spherules of meteoritic and volcanic origin

We have sampled dust deposits from five Pacific Coast volcanoes to search for and analyze microscopic volcanic spherules that might possibly be similar to the supposed meteoritic spherules found in polar ice sediments. In the size range 10 to 100 μ, approximately 2 × 10−5 of volcanic particles are perfect or nearly perfect spherules, and 2 × 10−3 of them are rough magnetic spheroids. Chemical analysis, using an electron-probe microanalyzer, shows them to be made up typically of some 0.4 Fe, 0.2 Si, 0.1 Al, 0.03 Ti, and 0.01 K. In composition they are similar to only a few of the polar glacier particles analyzed by us. In addition, we find that the numerical ratio of spherules to irregular particles for the volcanic dust is so different from that for the ice sediments that a volcanic origin for the latter seems impossible. Therefore, a meteoroidal origin for the arctic and antarctic spherules is still the most reasonable hypothesis.