A reserve of iron-rich meteorites could lie hidden beneath the surface of the Antarctic ice sheet, according to a study published in Nature Communications this week. The paper suggests that meteorites - key indicators of early Solar System formation processes - could lie trapped, out of sight, tens of centimetres beneath the ice surface.
Although meteorites fall evenly across the Earth’s surface, over two thirds (about 35,000) of the world’s total number of collected specimens have been recovered from Antarctica. This is primarily because ice flow dynamics transport meteorites buried at depth in the ice for hundreds of years, up to localised surface regions, known as Meteorite Stranding Zones (MSZs), allowing for efficient recovery. However, fewer iron-rich meteorites have been found in Antarctica compared to anywhere else on Earth. The reason behind their conspicuous scarcity in this region has remained unclear up to now.
Geoffrey Evatt and colleagues propose that this under-representation of iron-based meteorites might be the result of the Sun’s rays penetrating the clear ice in MSZs during the summer months and warming the iron-rich rocks more than non-metallic rocks. Such warming is hypothesised to melt the surrounding ice and cause the meteorite to sink, thus offsetting annual ice upwelling and permanently trapping the rocks below the ice surface. The authors combine laboratory experiments with mathematical models to show that thawing and freezing processes will typically negate all annual upward transportation of a MSZ meteorite with a high-enough thermal conductivity (e.g. containing iron), whilst allowing meteorites with lower conductivities to emerge from the ice.
The filtering mechanism identified by the authors indicates that sub-layers of ice tens of centimetres beneath the ice surface of a MSZ potentially contain iron-rich meteorites, which, if accessed, could aid our understanding of the early Solar System formation.