Have you ever wondered about the origin of life on Earth, and whether there is life elsewhere in the universe? There are countless planets in the galaxy, many of which are similar to Earth. However, no evidence of life has been found beyond Earth to date.
Scientists, specifically astrobiologists and astrochemists, are trying to answer some of these exciting questions. The three main topics in astrobiology are understanding the origin of life, habitability and limits of life, and signs of life.
The origin of life on Earth
As evidence for life beyond Earth is yet to be found, one of the ways to guide our search is through understanding the origin of life on Earth. Understanding abiogenesis, which is the transition from chemicals (e.g. phosphorus) to the prebiotic phase with molecular building blocks and finally to living systems that are capable of replication is the key. Researchers explored the environmental conditions of early planetary surfaces, and how they interact with prebiotic chemistry, particularly in the formation of essential building blocks of life such as nucleic acids and amino acids from elements and chemicals.
Habitability and limits of life
The other method of searching for extraterrestrial life is through identifying environments that are habitable and understanding how organisms cope with extreme environments. For example, scientists studied the life strategies of the microbial community on stone pebbles in the Atacama Desert, one of the most extreme environments on Earth with steep wet-dry cycles, huge temperature differences and high irradiation to provide perspective for the search for life beyond Earth and broaden the scope of “habitable”. One of the consensuses in the astrobiology community is that liquid water is required for life formation, either through exogenous sources such as comets or endogenous sources such as atmospheric synthesis. Efforts have been made to study the existence of water in ancient Mars, and the possibility of life in the subsurface of rocky planets. A recent research study showed that metal-rich stars are less likely to evolve complex forms of life on land compared to metal-poor stars due to the higher ultraviolet radiation on the planet’s surface.
Signs of life
Lastly, evidence of life beyond Earth could be harnessed by studying biosignatures of cells and their remnants derived from extraterrestrial samples.
Various missions have tried to detect organic matter on Mars and search for signs of extinct life in biomineralized or fossilized forms.
Conclusion and future prospect
Space experiments are commonly conducted in astrobiology research as the space environment allows long-term measurements and a specific space radiation environment that is difficult to replicate on Earth. With the commercialization of space and the advancement of space technologies, the costs of launching rockets have significantly lowered. This offers new opportunities to conduct long-term and more complex experiments in space, which would help to understand the origin and limits of life, as well as aid the search for biosignatures on other planets.