Extra-Terrestrial: Search for Signatures of Life

SCIENCESASTRONOMY & SPACE SCIENCEExtra-Terrestrial: Search for Signatures of Life

Astrobiology suggest that life is abundant in the universe and the primitive microbial life forms (beyond earth) could be found earlier than intelligent forms. The search for the extra-terrestrial life involves looking for biological signatures in the vicinity of solar system and looking for radio signals or technical signatures in far away deeper space. There is case for renewed emphasis on searching technosignatures of life in the universe.

If there is life beyond this planet ? This question has always intrigued people and there has been lot of sensationalism and media attention on extra-terrestrial life forms. But where does science stands? Now we have a full-fledged interdisciplinary area of astrobiology dedicated to the study of the origin, evolution, and distribution of life in the universe.

To the question If there is life beyond earth, there is optimism about the possibility of extraterrestrial life (Billings L., 2018). NASA Kepler telescope has shown that the habitable worlds are abundant in the universe. So are building blocks of life hence it seems reasonable to deduce that the life should be abundant in the universe.

Is it really possible to find extra-terrestrial intelligence? Yes, there is increasing possibility due to technological advancements (Hirabayashi H. 2019). Therefore there certainly is a case for search of life on other planets; the extra-terrestrial life form could be primitive or complex and intelligent. Estimates suggests that there is relative likelihood of success in the searches for primitive life form than intelligent one (Lingam and Loeb, 2019). The dominant thinking in astrobiology is that the “first contact” with extra-terrestrial life may be with microbial life elsewhere (Billings L., 2018).

How do we search them? The search for life in the universe currently involves two approaches – search for biosignatures (signatures of biology) in and around solar system and radio search for technosignatures (signatures of advanced life forms and technology) emitted from sources far away from solar system in the galaxy and beyond. Projects like Mars and Europa landers, James Webb Space Telescope are aimed at search for signatures of biology in nearby solar system while NASA’s SETI (Search for Extra Terrestrial Intelligence) program and the Breakthrough Listen (BL) project are examples of search for technical signatures in far deeper space.

Both approaches offer benefits but the search for technosignatures seems to complement search for biology but also expands search from solar neighbourhood to deeper in universe into galaxies.

The search for the technosignatures involving orientation, recording and analysis of radio signals or bursts emanating from deep space comes at relatively much lower cost (vis a vis search for biosignatures),. for example, the annual budget of NASA’s SETI program was about $10 million. Much of the space can be targeted and searched for radio signals with strong information content, robust detection and interpretations. Further, radio search has a established scientific background and context.

The case for search of technosignature is also made for the fact that search volume sampled so far is very low. The search volume could be expanded in near future. This would require enhanced access to radio telescopes, resources, rebuilding research ecosystem and keeping up with hardware and software advances (Margot et al 2019).


Editor’s Note:

Dr Jean-Luc Margot from UCLA has suggested ‘NASA does not have a SETI program. It has not had a SETI program in over 25 years. Please consider a correction.’.

We would like to add that NASA’s SETI program got cancelled in 1993. At that time SETI program’s annual budget was about $10 million.



1. Margot J et al 2019. The radio search for technosignatures in the decade 2020-2030. Pre-Print arXiv:1903.05544 submitted on (13 Mar 2019).
2. Billings L., 2018. From Earth to the Universe: Life, Intelligence, and Evolution. Biological Theory. 13(2).
3. Hirabayashi H. 2019. SETI (Search for Extraterrestrial Intelligence). Astrobiology.
4. Lingam M and Loeb A 2019. Relative Likelihood of Success in the Search for Primitive versus Intelligent Extraterrestrial Life. Astrobiology. 19(1).


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