If you are planning to work on finding life beyond Earth, this latest piece of work is just the thing you needed.

It is a well-known fact that scientists are exploring different parts of our universe in quest of finding alien life. The Kepler Space Telescope of NASA has found thousands of exoplanets, which may support life, since its launch in 2009. One of the most important factors which makes a planet habitable is its distance from its host star. It must be present in the Goldilocks Zone of the star to ensure that liquid water can exist at its surface. Among the discovered exoplanets, astronomers have found some rocky, Earth-sized heavenly bodies that are considered as potential candidates for extraterrestrial life and scientists are performing further research on them.

Recently, some of the leading experts of Planetary Habitability came up with a massive help for finding life on other planets as a series of 5 review papers was published in Astrobiology. These papers covered events from past, present, and future to provide a complete guidebook for searching life beyond Earth. They represent two years of work done by the Nexus for Exoplanet Systems Science (NExSS) and the Astrobiology Institute of NASA. They will serve as ‘Biosignatures’, which is a name given to the signs of life, for future telescopic observations.

The first paper was written by Edward Schwieterman, a postdoctoral researcher in the Department of Earth Sciences at the University of California. Contrary to a popular belief that only water is needed, he identified 3 types of Biosignatures that were used by previous astrobiologists to propose whether life could exist on a planet or not. First one of them is Surface Biosignatures. All the life-induced changes in the reflection and absorption of light on the surface of the planet fall in this category.

Then, we have Gaseous Biosignatures which include the presence of byproducts of life in the atmosphere of the planet. A perfect example of that is the production of Oxygen on Earth as a result of Photosynthesis done by plants. Lastly, we have Temporal Biosignatures which account for the time-dependent fluctuations in both gaseous and surface Biosignatures over a period of time. Talking about all the progress humanity has made in this field, Schwieterman said,

“In less than 30 years, we’ve gone from not knowing whether planets existed outside our solar system to being able to pinpoint potentially habitable planets and collect data that will enable us to look for the signatures of life. These advances offer unprecedented opportunities to answer the age-old question, ‘are we alone?’, but at the same time demand that we move forward with great care by developing robust models that allow us to seek and identify life with a high degree of certainty.”

He has pointed out all the difficulties that we face in searching for life on other planets as they are too far to visit, at least for now. He mentioned that the presence of false positives and false negatives makes it a whole lot more troublesome for us. He told the world that finding life through Biosignatures is not as simple as it may look. In order to make it more understandable for non-scientific people, he said that Oxygen is considered a possible indicator of life but the fact that it can be formulated through a number of non-biological methods makes it an ambiguous supposition. Similarly, life can be found in places where there is no Oxygen in the atmosphere. He also mentioned that this is the reason why Temporal Biosignatures are a whole lot more useful in such circumstances.

Schwieterman is a part of the Alternative Earths Astrobiology Center which is funded by NASA. The job assigned to them is to develop a ‘Search Engine’ for life on other worlds by making use of our 4.5 billion years old history. Despite all the differences in terms of climate and composition, all the chapters of Earth’s history have a commonality: Oceans have always been a home to an incredible diversity of simple and complex life. Timothy Lyons, the Director of the Alternative Earths Astrobiology Center, summed it up professionally by saying,

“We are using Earth to guide our search for life on other planets because it is the only known example we have. But Earth actually offers us a great diversity of possibilities. Rather than being constrained to a study of present-day life, we use geological and geochemical analyses to examine the billions of years that life survived, evolved, and thrived on Earth under conditions that are very different than today’s, hence the concept of ‘alternative Earths.’”