Extraterrestrial Components from Deep Sea Sediments of Indian Ocean

Abstract

Two different types of extraterrestrial particulate matter collections were undertaken during the last few years – by using
magnets encased in dredges that were dragged along the seafloor and by sieving massive quantities of deep sea sediments
from which cosmic spherules were subsequently isolated. Detailed investigations on close to 1000 sectioned cosmic
spherules revealed the presence of Pt-group nuggets in all the three basic types of cosmic spherules – all of whom had
carbonaceous chondritic meteorites as precursors, thus in a way unifying them. Further, Fe-Ni beads in all types of the
investigated cosmic spherules further confirmed this finding. Oxygen isotopes of relict-grains in silicate cosmic spherules
suggested chondrules from carbonaceous chondrites to be major contributors. In addition, relict chromite grains and dusty
olivines observed in several cosmic spherules suggested that at least 3% of the cosmic material that rains on the earth is
sourced from ordinary chondrites. The Australasian microtektites found in the Indian Ocean retained unique microimpact
features generated while they were in flight due to inter-particle collisions in the ejecta. This unique phenomenon outlined
the importance of the impact process during estimation of cosmic dust fluxes estimated from lunar materials.