Extraterrestrial organic compounds

The organic compounds in chondrites were originated from the interstellar media, and they were precursor components of the solar nebula. The organic compounds incorporated with other material into asteroids and planets by accretion processes. In the parent bodies of meteorites, organic compounds underwent various degrees of aqueous alteration and thermal metamorphism. Regardless of their abiogenic origin, extraterrestrial organic matter is very complex, consisting mainly of kerogen-like insoluble macromolecular materials with less abundant soluble organic material (SOM). Most of the SOM have identical counterparts in the terrestrial biosphere, but the former has distinct isotopic compositions of C, H and N, the critical evidence for their extraterrestrial origins. The irradiation of cosmic rays and UV light in the nebula and the secondary processes (e.g., aqueous alteration and thermal metamorphism) in meteorite parent bodies are the main contributions to the evolution of the organic matter. The extraterrestrial organic compounds have probably played a critical role in the origins of life. Meanwhile, Mars exploration has showed that at least the paleoclimate on Mars was favorable for the existence of microbes. In addition, several hints for past biotic processes were found in Martian meteorites. The first evidence of extraterrestrial life will likely be found on Mars in the future.