The global accretion rate of extraterrestrial materials in the last glacial period estimated from the abundance of micrometeorites in Antarctic glacier ice

Abstract

The accretion rate of micrometeorites in the last glacial period was estimated from the concentrations of micrometeorites in the blue ice around the Yamato Mts. in Antarctica. The samples from this study were collected from the five sampling points (M03, K02, K11, J09 and J10) in the blue ice. The blue ice was melted and filtered, and the micrometeorites were handpicked from the collected “glacial sands”. The weight of the micrometeorites in the blue ice was estimated from the abundance of recovered micrometeorites and the solar noble gas concentrations in the “residue” after handpicking. The age of the blue ice from the K area was estimated to be 27–33 kyr before present based on oxygen isotope data. The estimated accretion rate to the whole Earth ranges from 5300 × 103kg/a to 16000 × 103kg/a. However, the lower end of this range probably represents lower limits due to possible loss of solar noble gases during long residence in the glacier ice. Hence, we estimate that the accretion rate of micrometeorites 27–33 kyr before present to be in the range between (11000 ± 6600) × 103kg/a and (16000 ± 9100) × 103kg/a. These results, as well as the other estimates, suggest that the accretion rate of micrometeorites in the last glacial period was comparable to that in the present. Micrometeorite k]accretion rate k]Antarctica k]last glacial periods k]noble gas k]interplanetary dust particle