Low temperature spectroscopy and irradiation effects on Solar System ices - Kuiper belt objects as a case study

摘要

Since their discovery in 1992, Kuiper Belt Objects (KBOs)—small planetary bodies beyond the orbit of Neptune and 'precursors' to short periodic comets— have received considerable attention from the planetary sciences, astronomy, and physical chemistry community. At the low temperatures of KBOs of 30-50 K, a chemical modification of their surface ices such as water, nitrogen, carbon monoxide, carbon dioxide, methanol, and possibly ammonia is predominantly induced via non-equilibrium chemistry through ionizing radiation from solar wind particles, solar wind photons, and galactic cosmic ray (GCR) particles. Laboratory experiments simulating the interactions of ionizing radiation with icy surfaces at ultralow temperatures offer a remarkable opportunity for understanding the chemical processing of primitive bodies and allow for an establishment of a 'chemical' time-line dating back to the origin of our Solar System. Since pre-biotic molecules like amino acids and their precursors can be synthesized in these ices as well, those studies also explore scenarios where in our Solar System astrobiologically important molecules might have been synthesized since the formation of the Solar System 4.6 billion years ago.