As Earth orbits around the Sun, the Solar System revolves around the Milky Way’s center, moving through a continuously changing Galactic environment. In addition to its average velocity, the Solar System has a peculiar velocity relative to surrounding gas and stars, which causes it to traverse different regions of the interstellar medium (ISM) over time. The ISM is characterized by different gas and dust densities, temperatures, and pressures and is constantly shaped by a plethora of events and mechanisms, including supernova explosions, stellar winds, stellar radiation, Galactic shear, and magnetic fields. Encounters with dense gas regions, such as gas clouds or supernova shock fronts, can lead to various impacts on the Solar System. For example, the expected increase in the influx of interstellar dust into the Solar System and Earth’s atmosphere during one of the aforementioned encounters could potentially induce radionuclide anomalies on Earth. Moreover, increased extraterrestrial dust could directly alter Earth’s radiative balance, which, depending on the dust flux’s magnitude and composition, could produce distinct changes in climate. Finally, if the gas density encountered by the Sun is very high, the heliosphere could be compressed, directly exposing parts of the Solar System to the ISM.
Recent advancements in astronomy, geochemistry, and paleoclimatology highlight the importance of studying this topic. In astronomy, the European Space Agency’s Gaia mission has enabled major advancements, revolutionizing our understanding of the local Galactic environment. These achievements have led to the identification of previously unknown Galactic-scale gas structures and clusters (families) of stars, along with their relation to the past trajectory of the Solar System. In geochemistry, improved analytical techniques and new datasets have revealed anomalies in radionuclide and interplanetary dust records, some of which are already linked to astrophysical events, while others remain open questions. In paleoclimatology, new high-resolution records and modeling simulations representing the Earth system in the past are emerging. These advancements will aid in unraveling potential connections between our Galactic, Solar, and Terrestrial environments.
We aim to study and characterize the past and future Galactic environments encountered by the Solar System, identify possible connections between these environments and past changes in the Earth system, constrain the conditions under which interstellar densities can produce radionuclide anomalies or influence inputs of extraterrestrial particles to Earth, and foster interdisciplinary collaboration across these research fields.