  Recently Loeb et al. (2024, "Recovery and Classification of Spherules from
the Pacific Ocean Site of the CNEOS 2014 January 8 (IM1) Bolide", Res. Notes.
Amer. Astron. Soc. 8, 39) reported the magnetic collection of millimeter-sized
spherules from the seafloor near Papua New Guinea. About 22% had Mg/Si < 1/3
and were identified as a new "differentiated" variety of cosmic spherule
("D-type"). In a subset of 26 of these "D-type" spherules, 12 "BeLaU" spherules
were found to be dominated by Fe and Al, marked by low Si and even lower Mg
content, depletions of volatile species like Pb and Cs, and remarkable
enrichments of Be, La, U, Ba, and other elements. Loeb et al. claimed these
have exotic compositions different from other Solar System materials. We show
that in fact samples with these compositions are not just found on Earth, they
are from Earth; specifically, we identify them as microtektites of terrestrial
lateritic sandstone. Based on the location of the sample site, we associate
them with the Australasian tektite strewn field, generated 788 kyr ago by an
impactor that melted and ejected ~10^8 tons of sandstone, including a lateritic
layer, from Indochina. A tektite origin for the spherules is corroborated by
their terrestrial Fe isotopic compositions and the compound, non-spherical
nature of many of them, which preclude formation as ablation spherules from a
bolide. Due to the restriction of laterites to the tropics, iron-rich tektites
may be uncommon, but we predict they should comprise ~3% of the Australasian
microtektites.
