A potential hidden layer of meteorites below the ice surface of Antarctica

G W Evatt,P J Connolly,M J Coughlan,K H Joy,I D Abrahams,A R D Smedley

doi:10.1038/ncomms10679

Abstract

Antarctica contains some of the most productive regions on Earth for collecting meteorites. These small areas of glacial ice are known as meteorite stranding zones, where upward-flowing ice combines with high ablation rates to concentrate large numbers of englacially transported meteorites onto their surface. However, meteorite collection data shows that iron and stony-iron meteorites are significantly under-represented from these regions as compared with all other sites on Earth. Here we explain how this discrepancy may be due to englacial solar warming, whereby meteorites a few tens of centimetres below the ice surface can be warmed up enough to cause melting of their surrounding ice and sink downwards. We show that meteorites with a high-enough thermal conductivity (for example, iron meteorites) can sink at a rate sufficient to offset the total annual upward ice transport, which may therefore permanently trap them below the ice surface and explain their absence from collection data.

Highlights

Antarctica contains some of the most productive regions on Earth for collecting meteorites
When meteorites fall onto a large area of inland Antarctica, the subsequent ice flow dynamics direct many of them to localized surface regions called meteorite stranding zones (MSZs)[1]
With collection methods across Antarctica by different human searching programmes broadly similar, using visual inspection from snowmobiles or on foot, this further suggests that the physical cause for the disparity is more pronounced in regions of debris-free MSZ ice

Summary

Introduction

Antarctica contains some of the most productive regions on Earth for collecting meteorites These small areas of glacial ice are known as meteorite stranding zones, where upward-flowing ice combines with high ablation rates to concentrate large numbers of englacially transported meteorites onto their surface. While meteorite falls should be distributed almost uniformly across the Earth’s surface, meteorite collection data (see Table 1) reveals that the proportion of iron-based meteorites (iron meteorites and stony-iron meteorites) recovered from Antarctica, 0.7%, is significantly lower than the proportion recovered after witnessed falls (see Supplementary Note 2) from the rest of the World4–8, 5.5%—a statistical difference at over the 99.9% confidence level This comparison suggests that one or more physical mechanisms are resulting in an apparent shortfall of iron-based meteorite falls in Antarctica. This layer would lead to a significant increase in our library of iron and stony-iron meteorite types, which will directly help our understanding of early solar system-formation processes and the diversity of planetesimals that were present[14,15]

Methods

Results

Conclusion