Thursday, June 24, 2021

An overview of Astrobiology

We all feel fascinated when we hear the word aliens or extraterrestrial life, the detection of life outside our Earth has always been one of our primary quests in Astronomy or Science in general. While the idea of life out there has been bugging scientists for quite some time, some people have introduced a lot of unscientific/ pseudoscientific elements into it like conspiracy theories, unscientific claims, etc. These elements were never a part of science. We have a more formal discipline of study concerning Extraterrestrial life known as Astrobiology or Exobiology.

To give you a brief, astrobiology is an interdisciplinary field that concerns itself with study of life in the universe. It attempts to explain origins, evolution, distribution and future of life in the universe. One of the primary questions that Astrobiology seeks to solve is that whether extraterrestrial life actually exists and if it does then what could be the methods through which we could detect it. Astrobiology is an overlap of Biology and Astronomy. Astrobiology takes help of numerous scientific disciplines such as  molecular biology, biophysics, biochemistry, chemistry, astronomy,  cosmology, geology, etc.

➡ Astrobiology also includes  the study of the patterns of chemical evolution of ancestors of life, in the interstellar medium, and on the planets and small bodies of our solar system. 

➡ Astrobiology and Abiogenesis: 

Astrobiology also consists of studying the of life on Earth back to the very start, i.e Abiogenesis. As we know that the mechanisms involving Abiogenesis are not understood very well yet and much of the propositions of these mechanism are still in stage of hypothesis, we aim to get a clear understanding of Abiogenesis through Astrobiology. 

➡We can develop are more general guideline of how Abiogenesis occurs through Astrobiology. As the origin of life as we have studied is very specific to the environment of ancient earth, we should not expect life to arise the same way on other celestial bodies as it did on Earth.

When we are studying about the course of life in the universe we need to know about the origin of planetary systems as we need to peep into their habitable zones, we need insight into origin of organic compounds in space (Yes, we have detected some, it’s where Astrochemistry comes into play), research on biosignatures for the detection of life. 

➡ The Drake Equation and Astrobiology:

In 1961 Frank Drake proposed the following equation, to try to estimate the number of civilizations, N, capable of making radio communications in our galaxy where: N = number of civilizations in the galaxy that emit radio signals; R* = rate of star formation; fp = fraction of them with planetary systems; ne = number of habitable planets in each planetary system; fl = fraction of them that have developed life; fi = fraction of them that have developed intelligent life; fc = fraction of civilizations that perform interstellar communications; and L = length of time that these civilizations release detectable signals into space.

➡ The famous drake equation may look a little vague as we have not even discovered microbial life yet, but it’s very important in the field of Astrobiology, it formed the backbone of Astrobiology as a science It must be noted that  the usefulness of the Drake equation is not in the solving, but rather in the observation of all the various concepts which scientists must include when considering the question of life elsewhere, and gives the question of life a basis for scientific analysis. The equation has helped draw attention to some particular scientific problems related to life in the universe, such as abiogenesis, the development of multi-cellular life, and the development of intelligence.

➡Drake equation is of seminal importance because it is a 'road map' of what we need to learn in order to solve the fundamental question of life.

πŸ‘‰Let’s talk a little about the elements of Astrobiology πŸ‘‡

➡ Astrogeology: This field is concerned with the geology of the solid bodies in space, such as the asteroids and the planets and their moons. The information collected from Astrogeology helps measure a planet’s or a satellite’s ability to develop and sustain life.

➡ Astrochemistry: It is the study of abundance of molecules and their reactions in the Universe. Astrochemistry explains how molecular evolution occurred within various extreme astrochemical environments, such as the interstellar medium, the molecular clouds, the star-forming regions, and the planetary bodies. They examine the exotic chemistry occurring in the atmospheres and on the surfaces of planets, satellites, and other solar system bodies, e.g. comets and meteorites, that may nurture prebiotic molecules. Astrochemists study and detect organic molecules relevant to biology in space, and explore their implications for life on other planets.

➡ Cosmology: The establishment of cosmology as a science provided a parallel to the building-up of the scientific status of astrobiology. Prior to the discovery of the expansion of the Universe there was little that cosmology could contribute to the question of extraterrestrial life aside from probabilities. After our discovery of the expansion and evolution of the Universe the situation changed significantly. The entire cosmos was recognised as undergoing steady change. The history of the Universe took on the complexion of an unfolding in many stages, with the formations of first atoms and molecules, then galaxies and stars, and most recently, planets and life. The most important and simplest feature of the overall change in the Universe that the expansion produces is the rate at which it occurs. 

➡ NOTE:  

There are many other fields which Astrobiology takes help from, we could obviously not include all of them in one single presentation, also we did not include Biology and Astronomy as we assume that you posses a basic understanding of them.

➡While this overview of Astrobiology looks all good and it seems like there is ample of life in the universe, I would like to remind you of the fact that to date we have not detected any life/biosignatures beyond earth. 

Now there could be a ton of reasons that we have not detected life and this is an area where conspiracies began to flood.

➡The Fermi Paradox:

The Fermi Paradox highlights the apparent contradiction between the lack of evidence for extraterrestrial civilizations and various high estimates for their probability (such as the drake equation) 

Some of the points that highlight the apparent contradiction are:

•There are billions of stars in the Milky Way similar to the Sun.

• With high probability, some of these stars have Earth-like planets.

•Many of these stars, and hence their planets, are much older than the Sun. If the Earth is typical, some may have developed intelligent life long ago.

•Some of these civilizations may have developed interstellar travel, a step humans are investigating now.

•Even at the slow pace of currently envisioned interstellar travel, the Milky Way galaxy could be completely traversed in a few million years.]

•And since many of the stars similar to the Sun are billions of years older, the Earth should have already been visited by extraterrestrial civilizations, or at least their probes.

•However, there is no convincing evidence that this has happened.

➡ There are many proposed solutions to the Fermi Paradox, you can read them and about Fermi Paradox in detail in the our post of the Fermi Paradox, we will attach the link to that post at the bottom!

So, we come to end with this, hope you liked this small presentation of ours, also please note that Astrobiology is immensely complex and wide field and it is almost impossible to cover all of the contents into a single presentation though we hope you would have got a rough idea.

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