Signs of life beyond Earth? Astrophysicist urges caution

“We are either seeing the first signs of life beyond Earth — or uncovering an entirely new chemical process we’ve never seen before. Either way, it’s a breakthrough," summed up visiting British-Indian astrophysicist Nikku Madhusudhan, on one of the most significant discoveries he had made in modern astronomy.

Using the powerful James Webb Space Telescope, last year, his research team in the University of Cambridge detected possible biosignatures, the first signs of life on exoplanet K2-18b — which is situated at a distance of 120 light years from earth. This startling finding could very easily redefine humanity’s place in the universe and answer that age-old question – are we alone in the universe?

The Federal spoke to Nikku Madhusudhan, a professor of astrophysics at the University of Cambridge and an exoplanetary specialist, about the discovery, the caution behind the excitement generated over the discovery of alien life, and what it means for science and philosophy, and where India is at in the field of exoplanetary science. Here are the excerpts"

Why do you remain ‘cautiously optimistic’ about the possibility of life beyond our solar system?

What we have found recently with observations of this particular planet K2-18b are tentative signatures of excess absorption in its atmospheric spectrum. We think this could be from molecules like dimethyl sulfide or dimethyl disulfide, both of which are known biosignatures produced primarily by life here on Earth.

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So, we think it is possible that this planet may host life. But we also want to remain very cautious because these are very initial observations. The level of evidence is only at about 95 per cent confidence. In science, that is not enough. There is still a 5 per cent chance that what we are seeing is some random signal or something not related to life. We want to reduce that uncertainty to less than one in 100,000 or even one in a million. That’s the level of confidence we need.

What more evidence is needed to make this discovery definitive?

We need a lot more observations — repeated observations — to strengthen the signal. The idea is to ensure that what we are seeing is real and not a statistical fluctuation. If we confirm the presence of dimethyl sulfide and also confirm that it is produced only by life and not by any non-biological process, then that becomes a very strong case. Right now, we are not there yet. But, we are on the path, it is a beginning and that itself is significant.

If life is confirmed, what would it mean for humanity? Does it open a new era in the search for life?

If we confirm that a molecule like dimethyl sulfide is present and produced by life, it would answer one of the oldest questions humanity has asked: are we alone in the universe? That would be a huge moment.

It would fundamentally change how we see ourselves. Instead of thinking of the universe as a purely physical space filled with stars and galaxies, we would begin to see it as something that could host life elsewhere — like oceans or forests on Earth. Our perspective would shift from being Earth-centric to being part of a larger, living cosmos. We would realise we are just one part of a much bigger system and that would change how we look at the cosmos.

Can you explain what Hycean exoplanet worlds are? This is a word you coined is it not?

The word “Hycean” is a combination of hydrogen and ocean. These are planets that have a hydrogen-rich atmosphere and an ocean-covered surface.

This is a unique type of planet — we don’t have anything like this in our solar system. That’s why we coined the term. They are particularly exciting because they may be more conducive to detecting signs of life with current technology than rocky earth like planets.

Traditionally, the focus has been on finding Earth-like planets. But realistically, detecting life on Earth-like planets is still about 20 years away in terms of capability. With Hycean worlds, we have brought that future to the present. These planets are observable with current instruments like the James Webb Space Telescope. So yes, they offer a more immediate pathway to searching for life.

What are the updates on K2-18Bafter your discovery in April 2025?

After the initial findings, there was a lot of excitement — even exaggerated claims about finding aliens. That reaction is understandable, but it also highlights why we need to be cautious. Since then, several studies have tried to challenge or reinterpret our findings. For example, one study suggested we may not have considered enough molecules and looked at 90 possible candidates.

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So we went further and analysed 650 molecules — the largest such analysis ever done in this field. We used both near-infrared and mid-infrared data.

Even then, only three molecules showed significant signals, and dimethyl sulfide was one of them again. The other two are also complex molecules often associated with life or industrial processes. So, no matter how we look at it, we are seeing something complex. Either it is life, or it is a chemical process we don’t yet understand. Both are major discoveries. The very act of discovering two or more prominent carbon-bearing molecules in a planet within the habitable zone of its host star and therefore potentially habitable is a big deal.

Has there been skepticism about your research?

Absolutely, and that is a good thing. Science progresses through skepticism. We actively engage with alternative explanations. In fact, we ourselves try to disprove our findings repeatedly. If others bring valid counterarguments, we take them seriously. The goal is not to prove we are right — the goal is to find the truth.

The goal is not to find life at any cost. The goal is to understand what is actually out there. If it turns out to be life, that is extraordinary. If it turns out to be a new chemical process, that is also a major breakthrough. Either way, we learn something fundamentally new about the universe.

How has the James Webb Space Telescope helped in your discoveries on exoplanets?

The James Webb Space Telescope (JWST) is the largest telescope that space humanity has ever built. This is leading to advancements across astronomy, more especially in the study of exoplanetary science, for example this is the telescope that was used to first detections of carbon bearing molecules methane and carbon dioxide in the atmosphere of the planet K2-18B. This exoplanet is two and half times larger than earth but it is temperatures which is roughly similar to earth and we feel that this planet might be habitable.

Several other such observations across exoplanetary science and it is leading to major breakthroughs in our understanding of planets and their atmospheres in planetary systems, around stars beyond our solar system.

How has your work on exoplanets shaped your perspective on humanity’s place in the universe?

Right now, when we look at the night sky, we see a vast but lifeless universe — stars and galaxies that are physical objects.

If we find life elsewhere, that changes everything. The sky would no longer feel like an inanimate space. It would feel alive - it will be like a living sky.

That would expand our identity — from being a species on Earth to being part of a cosmic ecosystem. Even finding life on one planet would imply there are many more such worlds.

Where does God fit into this vast expanding cosmos?

I don’t see any contradiction. Different religions have different interpretations of God.

One could argue that God represents the ultimate reality from which everything has arisen. If that definition includes the entire cosmos, then whatever we discover is part of that same reality, I believe. So I don’t see a conflict between science and the idea of God.

Why are you not drawn to science fiction like the film, Project Hail Mary or Inception, despite working in such a fascinating field?

For me, my work itself is at the cutting edge of science. I am daily dealing with fascinating ideas ideas and discoveries that are often stranger than fiction.

So I don’t feel the need to seek that inspiration elsewhere. My “science fiction” becomes real science very quickly.

What role is India playing in exoplanet research?

There is already a lot of work happening — from planet formation to atmospheric studies. Over the past decade, the progress has been enormous. Indian researchers are working at global standards, and the country is quickly becoming a major player in this field. India is also planning new missions related to exoplanet science.

India is growing at a phenomenal pace in both space missions and space science. There are increasing opportunities through ISRO missions, astrophysics research, and ground-based telescopes for students. The future is very bright, especially for young scientists.

Students can start with master’s and graduate studies in institutions working on exoplanet science. There are also opportunities in ISRO and other labs, especially in instrumentation and mission development.

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