Astrobiology is an interdisciplinary field that aims to understand the origin and evolution of life on Earth and elsewhere in the Universe. It combines research from biology, biochemistry, organic chemistry, inorganic chemistry, astronomy, astrophysics, and astrochemistry, in order to bring answer to the origin and evolution of life in the most possible general way and using approaches from different angles.
Through astronomical observations, we know that ices are ubiquitous in the Universe’s cold environments and mainly composed of H2O (most abundant component), CH3OH, CO, CO2, NH3, CH4, as well as other small and more complex species that condense on the surface of cold, silicate or carbonaceous grains. Ionizing radiation in the form of UV photons or cosmic rays (energetic particles such as protons and other atomic nuclei) that interact with such ices alter their chemical composition and result in the formation of new, more complex species.
Laboratory experiments conducted since more than 20 years in which astrophysical ice analog mixtures consisting of H2O, carbon sources (CO, CO2, CH3OH, etc.), and nitrogen sources (NH3, HCN, etc.) are irradiated with UV photons or bombarded with energetic protons have shown that numerous new molecules are formed and can be identified. Among those compounds, several complex organics such as amino acids, carboxylic acids, amphiphilic compounds, nucleobases, and sugar-related compounds were found in the residues that are recovered at room temperature after warming up the samples.
Most of these compounds have also been found to be present in carbonaceous meteorites, suggesting that such meteoritic compounds were formed abiotically under astrophysical conditions via processes that are similar to those simulated in the laboratory. The presence of such a wide variety of prebiotic compounds in meteorites also supports a scenario in which comets and asteroids may have seeded the primitive Earth, as well as maybe other telluric planets around other stars, with all the material needed to trigger the first reactions leading to the emergence of life on our planet. Although the processes leading to biological systems from a chemical inventory pool are not fully understood yet, the fact that it happened on Earth several billion years ago is a good incentive to think that it may also have happened elsewhere at some point in the history of our Universe.
By Dr. Michel Nuevo