Final Report Summary - ASTROGEOBIOSPHERE (An astronomical perspective on Earth's geological record and evolution of life)
We are performing the first reconstruction of the variations in the flux of different types of meteorites to Earth through geological time. We have built the world's first laboratory for recovering thousands of mineral grains originating from different parts of the solar system at different times through Earth's history. The grains are recovered from large samples of ancient sediments that are dissolved in acids. We have shown that the type of meteorites falling on Earth about 500 million years ago were as different from those falling today, as life was different compared to today. The meteorites that fell 500 million years ago are dominantly achondrites that are very rare on Earth today. We have also located "extinct" meteorite types whose parent bodies have been consumed by collisions. The observed turnover in the meteorite flux from dominance of achondrites to dominance of the ordinary chondrites today represents a major conundrum in our understanding of how the late solar system has evolved. Our project is establishing the first "meteorite stratigraphy", that complements existing bio-, chemo- and magneto-stratigraphies for Earth's geological record. In our project we have been able to relate, with a very high temporal resolution, ancient events on Earth with events in the solar system, such as asteroid parent-body breakups or perturbations of the orbits of planets and orbital resonances. We have observed that the onsets of the major ice ages the past billion years tend to coincide with disturbances of the asteroid belts, as observed in changes in the meteorite flux. This represents the first empirical evidence that large-scale astronomical disturbances of the solar system may have triggered the ice ages. The traditional view has been that the ice ages are related to changes in ocean circulation or in the concentration of atmospheric carbon dioxide. By linking the changes in the meteorite flux and ancient events on Earth to the results of the recent Gaia mission, where billions of stars in our galaxy will be mapped, we are aiming at an integrated history for Earth, the solar system and the galaxy.