Geochemical evaluation of cosmic spherules collected from the Central Indian Ocean Basin

Abstract

Micrometeorites (MMs) significantly contribute to the extraterrestrial material the Earth receives and represent a broader range of precursors than known meteorites. Low sedimentation rates prevalent in the deep-sea regions far away from land provide a unique opportunity for collecting MMs from these least disturbed regions. In the present study, we have studied 305 cosmic spherules recovered from the Central Indian Ocean Basin (CIOB); that have undergone melting during hypervelocity entry into the Earth's atmosphere. During the atmospheric entry, primary signatures of MMs are lost depending upon the extent of heating, complicating the identification of the parent body. Nevertheless, we have tried to relate these cosmic spherules to their respective parent bodies based on elemental ratios present in them, considering atmospheric ablative losses of various elements. The chemical analyses indicate that many deep-sea cosmic spherules are linked to carbonaceous chondrites. Around 239 porphyritic olivines (PO), 42 relict olivines are studied for their textural development and composition during recrystallisation during atmospheric entry. Thirty-zoned olivines are analysed from rim to core to understand various elements behaviour during atmospheric entry. Seawater plays a vital role in eroding these cosmic spherules material, and its effect is also discussed. As most of the recent micrometeorite collections focus on the polar region, these deep-sea spherules will significantly add to the information about the extraterrestrial matter reaching the Earth.