Astrobiology

As an extremely inquisitive child, I would often bother my mother with endless questions related to the universe and the existence of life. My mother would very patiently answer them to the best of her capacity. Eventually most of them were answered by Google, of course, yet, some questions remained unanswered, including:

“Are we alone in the universe?”

I am sure all of you, or at least most of you must have encountered this mind-boggling question, leaving you sleepless for nights. The question whose answer has not been found yet, the question which can make you feel overwhelmed about your mere existence. For those who have not encountered this question, please take a moment to think about it. You do not have to be another Sagan to answer this question, all you need to do is think of the endless possibilities and you are a step closer to the answer.

Astrobiology helps you get scientifically closer to the answer. Astrobiology is the study of origin, evolution, distribution and future of life on earth. It also discusses the existence of extra-terrestrial life. Astrobiologists from different scientific disciplines work together to examine complex questions which no one field can answer alone. These questions are complementary to our main question, including:

How does life originate?

How does life evolve?

What kind of environment is necessary for life to survive?

What are the environmental limits or “extremes” under which life can survive?

What might life look like on another world?

Is there or has there been life elsewhere in our solar system?

How can we observe and identify a habitable – or even inhabited – world?

What is humanity’s future on Earth and beyond?

There has been profound research on the evolution of life on Earth. It is agreed that all life on earth evolved from a single primitive life form. LUCA (last universal common ancestor) is the most recent common ancestor of all life forms on earth, but it should not be assumed to be first life form on earth. There are many hypotheses and theories which have been established over the time and we are going to take a quick look at them. So, to begin with, we have the theory of Special Creation. It was believed that life originated on Earth in a supernatural event. According to most myths, the non-living world was created first and then came the creation of life. Elaborating on the myths from the theory of special creation was the Catastrophe theory. Next was the theory of Spontaneous Generation which propagated that life originated spontaneously from non-living matter. These theories may seem irrational to us today, but back then they were believed to be true. After these seemingly crazy theories came a more sensible one - Biochemical theory, which gave a better perspective, that the original spark of life may have begun in a warm little pond, with all sorts of ammonia and phosphoric salts, light, heat, electricity, etc. A protein compound was then chemically formed ready to undergo still more complex changes.

All the above-mentioned hypothesis state that “life” originated on earth, but is it possible that life originated elsewhere? Well, yes! According to Panspermia life exists throughout the Universe, which is distributed by meteoroids, asteroids, comets, planetoids, and also by spacecraft in the form of unintended contamination by microorganisms. Panspermia explains that microscopic life forms that can survive the effects of space, such as extremophiles, become trapped in debris ejected into space after collisions between planets and other small bodies that harbour life. Some organisms may travel dormant before colliding randomly with other planets. Under certain ideal impact circumstances (for example, into a body of water), and ideal conditions on a new planet's surfaces, it is possible that the surviving organisms could become active and begin to colonize their new environment. This is one of the very possibilities by which life could have originated on Earth.

We mentioned earlier about extremophiles, these are generally of keen interest to astrobiologists, as many organisms of this type are capable of surviving in environments similar to those known to exist on other planets. For example, Mars may have regions in its deep subsurface permafrost (rock or soil, at or below freezing point of water) that could harbour certain kind of life. The subsurface water ocean of Jupiter's moon Europa may harbour life, especially at hypothesized hydrothermal vents at the ocean floor.

Research into the environmental limits of life and the workings of extreme ecosystems is ongoing, enabling researchers to better predict what planetary environments might be most likely to harbour life. Missions such as the Phoenix lander, Mars Science Laboratory, ExoMars, Mars 2020 rover to Mars, and the Cassini probe to Saturn's moons aim to further explore the possibilities of life on other planets in our Solar System. Advancements in the fields of astrobiology and the discovery of large varieties of extremophiles which are capable of thriving in the harshest environments on Earth, means that life may possibly be thriving on other planets in the universe already! Exciting isn’t it?

Something more exciting is the Drake equation, which emphasizes on the high chances that life already exists elsewhere. It states that “The universe has 10 million, million, million suns (10 followed by 18 zeros) similar to our own sun. One in a million has planets around it. Only one in a million million has the right combination of chemicals, temperature, water, days and nights to support planetary life as we know it. This calculation arrives at the estimated figure of 100 million worlds where life has been forged by evolution”.

So again, “Are we alone in the universe?”.