3rd Year Biotechnology Student
Thadomal Shahani Engineering College
Some of you might wonder what astrobiology is. The modern term ‘astrobiology’ was familiarized by Wes Huntress at the NASA headquarters in 1995. NASA describes astrobiology as the study of the origins, evolution, distribution, and future of life in the universe. It is the branch of science involved in the study of the origin and evolution of life on Earth and the possible diversity of life elsewhere in the Universe.
Although the concept of astrobiology emerged in full force in the 1990s, it is not a new idea, no matter how bizarre it might sound. Thales (c. 600 BC), frequently referred to as the Father of Western Philosophy, advocated the concept of the plurality of worlds containing life. The Greek scholars Leucippus, Democritus and Epicurus also supported this pluralism. Metro Dorus (c. 400 BC), a student of Democritus wrote ‘It is unnatural in an extensive field to have only one stalk of wheat, and in the infinite universe only one living world’. These views were shot down by Plato and Aristotle, and for over a thousand years people believed that the Earth was the center of the Universe.
When the renaissance scholars determined that the earth orbited the sun, it began renewed conjectures about extraterrestrial life. Johannes Kepler (1571–1630), Christiaan Huygens (1629–95) and Immanuel Kant (1724–1804) believed in life on the various other planets of our solar system. The late 19th century showed a growing interest in life on other planets from a scientific perspective, but a lack of visible success resulted in this interest fading once again during the mid-20th century.
Astrobiology nurses the challenging issue of what exactly is ‘life’. The attributes of life can be listed as growth, responsiveness, reproduction, adaptation, structured order of cells and energy utilization (metabolism). But all of these are what life performs or executes, not what life ‘is’. They are also not exactly unique to living organisms. Growth can be seen in a bushfire, responsiveness and adaptation can be seen in a river bed where the water cuts a path through rock, many couples don’t have children and are perfectly happy without reproducing, structured order of cells can also be seen in crystals, and machines utilize energy in the form of fuel metabolism. All this proves that we can’t define life based on these properties (Catling, 2013).
Erwin Schrödinger said that every living organism must have some sort of code to run on, which we now know is called the genome of an organism. Genome is an inheritable blueprint of life, capable of minor errors to facilitate evolution through the generations. This brings us to the two, in-use definitions of life, ‘a self-sustaining chemical system capable of Darwinian evolution’ and ‘a self-sustaining, genome-containing chemical system that has developed its characteristics through evolution’. The second definition was brought into the picture due to the fact that the first one wouldn’t be of any use in formulating an experiment.
It is believed that life originated on Earth around 4 billion years ago in the tepid oceans present at that time. This is hypothesized to have happened due to soluble organic compounds present in ocean waters interacting with each other, transferring chemical information, and making errors required for evolution. The issue here is that we don’t know how many compounds were used for the initial creation of life, and they have since been expunged from Earth. For this genesis to be replicable on another suitable celestial body, it will have to start with a small number of molecules and it will have to be a fast reaction. If genesis of even single-celled primitive life forms required a multitude of molecules and centuries of time, this phenomenon may be unique to Earth.
There have already been a few experiments to analyze if microbes can survive the harsh conditions of outer space. The Tanpopo mission has provided conclusive evidence that Deinococcus aetherius can survive after a yearlong exposure to the extreme conditions of the orbit of the International Space Station (ISS) (Yamagishi et al., 2018). The Tanpopo mission objectives were to test the panspermia hypothesis and to analyze if organic compounds may have been transported to Earth before the origin of life (Yamagishi et al., 2018). Their experiment has been a huge step forward for scientists in the field who are trying to find evidence of life beyond Earth. But they are not the only ones to perform such experiments. Another study demonstrated that Halorubrum chaoviator and Synechococcus (Nägeli) survived space vacuum for two years at the ISS with 90 ± 5% survival rate (Mancinelli, Horneck, Panitz, & Martins, 2015). Even though this rate was seen only in the samples kept unexposed to UV-radiation, it still shows a remarkable ability of microorganisms to survive and thrive even when faced with such inhospitable conditions (Mancinelli et al., 2015). These findings are instigating evaluation into the known origin of life on our planet.
Many scientists are now convinced that microbial life is not confined to Earth. But without proof, it is just a hypothesis. Even now, scientists are on the lookout for planets that are capable of supporting multicellular, complex life forms, and a recent study (Schulze-Makuch, Heller, & Guinan, 2020) has theorized that a list of 24 planets or planet-like objects seem to have some or all the properties required to be superhabitable. Of these, only one Kepler Object of Interest (KOI), namely KOI 5715.01, seems to fit all the criteria for habitability. Although it has a lower overall predicted temperature than Earth, if it has a stronger greenhouse effect, it will be a strong contender for our search for extraterrestrial life.
These ventures have dipped into the possibility of life beyond Earth, and if we continue down this path, we are likely to encounter success. What will happen when we do is yet to be determined.
About the author:
Siddhi Bhutada is a third year Biotechnology student from Thadomal Shahani Engineering College. Her aim is to work in cancer genetics, in the targeted medicine field. She has published a paper titled ‘Applications of Immunoglobulin Isotypes in Cancer Immunotherapy – A Review’ last year and is currently working on another publication on Horizontal Gene Transfer. She is extremely passionate about research and is working hard to accomplish her goal of leading her own research team in cancer therapeutics.