Abstract
Dust dominates extraterrestrial flux on the earth (30,000 tonnes/yr), however only ~5% of the cosmic dust survives atmospheric entry which is basically in two forms: melted and unmelted. Melted micrometeorites undergo transformational changes due to heating during atmospheric entry which obliterate evidences regarding their precursors. Unmelted micrometeorites (UMM) survive atmospheric entry with minimal alteration, they provide direct evidence for their parent bodies. Recent investigations unravelled a wide range of UMM, there are however no quantitative estimates of sources that contribute to the cosmic dust accreted by the Earth.
Highlights
We present an unmelted micrometeorite collection that has so far the widest known range, comprising of a complex association of fine-grained scoriaceous particles, chondrules, composite particles, glassy meteorite matrices, individual mineral grains, refractory minerals and metal micrometeorites
Unmelted micrometeorites (UMM) from the polar regions enabled the identification of particles from different sub-groups of carbonaceous chondrites[4,5], ordinary chondrites[2,6,7,8], and from basaltic achondrites[9]
The magnetic fractions from five of these sediment samples were examined that led to the discovery of 195 UMM
Summary
During our earlier investigation[4], we sieved 293 kg of deepsea surficial sediments of the Indian Ocean from ten closeby locations. We isolated 481 cosmic spherules from these samples[4] These sediments covered a volume of 50 × 50 × 15 cm of the deepsea floor and based on the rates of sedimentation in this area, they were assigned a terrestrial age of 0 - ~50,000 years. The magnetic fractions from five of those samples (Table 1), from which the spherules have been removed, are examined for unmelted cosmic particles. These samples cover a volume of 250 × 250 × 15 cm of the seafloor and by virtue of the earlier assigned dates[4], they all have a terrestrial age range of 0 – ~50,000 years.
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
