If you have problems with this question, check Chapter VI.8B,C in the Review 9. The laws of gravitation could be studied from how fast the meteorites fell to the ground. Until very recently meteorites were the only matter from outer space which could be studied in the laboratory. The impact of meteorites produce most of the earthquakes. If you have problems with this question, check Chapter VI.8C in the Review 10.
Iridium is poisonous for dinosaurs.
Iridium is much more abundant in meteorites than in the Earth's crust. Iridium is created in the melting of the Earth's crust during a meteorite impact. Iridium is dug out of the Earth's interior during a meteorite impact. If you have problems with this question, check Chapter VI.8C in the Review 11. If you have problems with this question, check Chapter VIII.2A in the Review 12.