Terrestrial weathering rates defined by extraterrestrial materials

In studies attempting to quantify the effects of climate on weathering rate, meteorites offer a number of advantages over terrestrial rocks—material from one outcrop (in this case, an asteroid parent body) delivers samples of similar composition and texture over the whole of the Earth's surface, in all climatic regimes; the starting composition prior to weathering is known in detail; the terrestrial residence time may be accurately determined from cosmogenic radionuclides; and the degree of weathering can be tracked by measuring the abundance of ferric iron. When analysing meteorites found in different deserts, we can discriminate a range of weathering rates. We observe a rapid initial weathering phase with the majority of weathering occurring in the first few hundred years after fall. Although the overall degree of weathering and the suite of weathering products observed will be specific to meteorites, the relative differences in weathering rate between different sites should be similar for terrestrial rocks.