Can meteorites tell us what is inside Earth?
Yes. Iron meteorites are samples of planetary cores, and chondrites show the raw materials Earth was built from, helping scientists estimate the composition of Earth's interior.
Nobody can drill to Earth's core, about 2,900 kilometres down. Even the deepest borehole, in Russia, reached only about 12 kilometres. So how do scientists know what Earth's interior is made of? Meteorites provide crucial clues.
Cores. Iron meteorites are pieces of the metal cores of small planetesimals that melted and separated. They show what planetary cores are made of: mainly iron with about 5 to 30 per cent nickel, plus sulfur, phosphorus and carbon. Earth's core is similar but must also contain lighter elements, because seismic waves show it is less dense than pure iron-nickel at those pressures.
Building blocks. Chondrites represent the undifferentiated material from which planets formed. By assuming Earth was built from chondrite-like material, scientists estimate its bulk composition. Subtracting what is known about the crust and mantle gives estimates for the core.
Mantle analogues. Pallasites, with olivine and metal, and some achondrites give insights into mantle minerals and how metal separated from rock.
Deep-Earth minerals. Shock veins in some meteorites contain high-pressure minerals, such as ringwoodite and bridgmanite, that are thought to make up much of Earth's mantle but are otherwise unreachable. Bridgmanite was first found in nature in the Tenham meteorite.
Timing. Isotopes such as hafnium and tungsten, measured in meteorites and Earth rocks, show that Earth's core formed within roughly the first 30 to 100 million years.
Together, meteorites and seismology give a much clearer picture of our planet's hidden interior.