Did meteorites foster life on Earth?

About 470 million years ago -- back when the Earth was ruled by insects and our ancestors were jawless fishes -- our planet was pounded by a series of enormous meteorites. The traces of that hammering survive today in ancient rocks in central China and southern Sweden, where researchers have found exotic mineral grains found only in meteorites. This week in the journal Nature Geoscience, scientists report that the impacts coincided with a drastic change. The diversity of life on Earth took a sharp climb right after the meteorites started falling.

From the paper:

The rise and diversification of shelled invertebrate life in the early Phanerozoic eon occurred in two major stages. During the first stage (termed as the Cambrian explosion), a large number of new phyla appeared over a short time interval 540 Myr ago. Biodiversity at the family, genus and species level, however, remained low until the second stage marked by the Great Ordovician Biodiversification Event in the Middle Ordovician period. Although this event represents the most intense phase of species radiation during the Palaeozoic era and led to irreversible changes in the biological make-up of Earth's seafloors, the causes of this event remain elusive. Here, we show that the onset of the major phase of biodiversification 470 million years ago coincides with the disruption in the asteroid belt of the L-chondrite parent body -- the largest documented asteroid breakup event during the past few billion years. The precise coincidence between these two events is established by bed-by-bed records of extraterrestrial chromite, osmium isotopes and invertebrate fossils in Middle Ordovician strata in Baltoscandia and China. We argue that frequent impacts on Earth of kilometre-sized asteroids -- supported by abundant Middle Ordovician fossil meteorites and impact craters -- accelerated the biodiversification process.

Read full paper in Nature Geoscience