External forcing to the Earth system evolution—Odyssey of the Earth II

Just as understanding national history requires a global context, studying Earth’s evolution must account for extraterrestrial factors. The rapid advancement of space science and technology in recent decades has enabled an unprecedented convergence of astronomy and Earth sciences. The time has come for a more holistic approach of extraterrestrial processes as external driving forces for the evolution of the Earth system.During Earth’s formation, the early Solar System was highly unstable ─ a fact evidenced by the impact origin of the Moon. Later in Earth’s history, the asteroid belt became the dominant source of instability affecting our planet. The most noticeable phenomena are impact events caused by extraterrestrial bodies, reflecting how the evolutionary history of asteroid families influences Earth’s environment. Indeed, many major climate transitions throughout Earth’s history were driven by such extraterrestrial events. An example is the Chicxulub crater in Mexico, which records the impact event 66 million years ago that led to the mass extinction of dinosaurs. Beyond surface craters and meteorites, dust produced by collisions within the asteroid belt can also profoundly influence climate and the biosphere as revealed by geochemical signatures in geological records. While the efforts of locating meteorites and impact craters will continue, emphasis should also be placed on geochemical methods ─ particularly trace elements and isotope analyses.The detection of numerous exoplanets has highlighted the distinctive architecture of our own solar system. This uniqueness stems from an early solar system event known as the Jupiter’s “Grand Tack”, which positioned Earth and other inner planets within the “habitable zone” and led to the formation of the main asteroid belt. Although the era of major planetary migration has ended, chaotic gravitational interactions among Solar System bodies continue to affect Earth’s climate through orbital variations. This has inspired an emerging research direction: reconstructing the long-term evolution of celestial motions from geological records.Another major discovery is that organic molecules can be synthesized directly within interstellar nebulae, implying that life may not have originated on Earth. It is plausible that the emergence of life represents a new phase in cosmic evolution, with origins potentially beyond our planet. Perplexing, life appeared on Earth roughly a billion years after its formation, yet the evolution from prokaryotes to eukaryotes—or the formation of the cell nucleus—took additional two billion years. This irregular pace of evolution seems difficult to explain through terrestrial processes alone, making an extraterrestrial origin of life a compelling alternative.We believe that deeper integration of astronomy and Earth will form a cornerstone of the “upgraded Earth system science”. However, bridging the considerable gap between these disciplines poses immense challenges. They differ profoundly in spatiotemporal scales, methodologies, and even terminology. A phased approach is therefore recommend ─ starting with small-scale projects and workshops to fertilize interdisciplinary collaboration, with the ultimate goal of achieving transformative scientific breakthroughs in uncovering the roles of extraterrestrial forcing in the evolution of the Earth system.