Journal Article 1 Mention
The flux of meteorites to the Earth over the last 50 000 years
P. A. Bland1996
Thomas SmithA. J. T. Jull
Top 5% · 95th percentile
142 citations · Astronomy and Astrophysics
Open Access

TLDR

Meteorites have been falling to Earth at a steady rate for at least 50,000 years, and scientists can estimate how many arrive each year by studying how they weather in deserts.

Summary

1 Study Aim

The main goal of this paper is to determine how many meteorites have fallen to Earth over the past 50,000 years. The authors aim to do this by analyzing meteorites found in desert regions, measuring how much they have weathered (changed due to Earth's environment), and using this information to estimate the rate at which meteorites arrive on Earth. Scientists wanted to figure out how many meteorites hit Earth each year by looking at old meteorites found in deserts.

2 Study Design

The researchers studied 98 ordinary chondrite meteorites (a common type of stony meteorite) from three dry regions: New Mexico, the Sahara, and the Nullarbor Region in Australia. They used carbon-14 dating (a method to find out how long a meteorite has been on Earth) and Mössbauer spectroscopy (a technique to measure how much the meteorite has rusted or oxidized) to determine how quickly meteorites break down in these environments. By comparing the number, size, and age of meteorites found, they calculated how many meteorites of a certain size fall each year. The team collected and analyzed meteorites from deserts to see how fast they break down and used this to estimate how many fall each year.

3 Findings

The study reveals that between 36 and 116 meteorites larger than 10 grams fall per million square kilometers each year. This means that, for the whole Earth, thousands of meteorites in this size range arrive annually. The total mass of meteorites falling to Earth in the 10 gram to 1 kilogram range is estimated to be between 2,900 and 7,300 kilograms per year. The results from different desert regions agree closely with each other and with previous estimates from camera networks. The authors conclude that the rate at which meteorites fall to Earth has stayed about the same for at least 50,000 years. They also suggest that their method could be used in Antarctica to study even longer time periods. The research shows that meteorites have been hitting Earth at a steady rate for a very long time, and this can be measured by studying how they weather in deserts.

Abstract

98 ordinary chondrite finds, terrestrial age-dated using 14C analyses by Jull et al., from three arid/semi-arid meteorite accumulation sites (New Mexico, the Sahara, and the Nullarbor Region, Australia) have been examined by Mössbauer spectroscopy to determine quantitatively the terrestrial oxidation for each sample. A comparison of weathering over time, and its effect in ‘eroding’ meteorites, allows a calculation of a decay constant for meteorites from each hot desert site. This, together with the number and mass distribution of paired meteorites in each region, enables us to derive estimates of the number of meteorite falls over a given mass per year: we calculate between 36 and 116 falls over 10 g per 106 km2 yr−1. In addition, we constrain the total mass flux to the Earth's surface over the 10 g to 1 kg interval to between 2900 and 7300 kg yr−1. We find remarkable agreement in our estimates from each accumulation site, and also with the estimate of the present flux made from MORP camera network data presented by Halliday, Blackwell & Griffin, suggesting that the flux of meteorites to the Earth has remained essentially constant over the last 50 000 yr. This work is the first independent confirmation of the MORP estimate, and indicates that meteorite accumulation sites provide an alternative method of calculating flux. We suggest that the application of a similar methodology to the Antarctic meteorite population may be used to explore the possibility that the flux of meteorites to the Earth has varied over the 1-Ma time-scale sampled by these meteorites.

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