From Sci-Fi to Reality: Have We Just Found Signs of Alien Life?

DMS: A molecule tied to life on Earth… now found 120 light-years away.

We have been fascinated by the idea of life beyond Earth and the possible war between humans and aliens in various Sci-Fi movies and TV series. But a persistent question still remains:

Do living organisms exist beyond Earth?

This question has haunted human imagination for centuries. From ancient scripts to modern science fiction, the idea that life may exist elsewhere in the cosmos has inspired countless philosophical and scientific theories. However, advancements in fundamental science and observational tools over the past few decades have allowed us to investigate those possibilities thoroughly.

A Brief Historical Prelude

The invention of the telescope in the early 17th century opened a new window to observe stars and planets more closely. Galileo’s observations, like the craters on the Moon and the four moons of Jupiter, hinted that other celestial bodies might have their own unique worlds, and they may support different forms of life. This curiosity drove researchers to explore the planets and moons in our solar system, and a new branch of planetary science came into picture.
Further in the 20th century, the discovery of extremophile organisms, microbes that thrive in some of Earth’s most extreme environments, has completely reshaped our view on the existence of life. If life can survive in boiling hydrothermal vents or beneath the frozen layers of Antarctic ice, then it may also exist on Mars, Europa, or even in the cloudy skies of Venus.

The Rise of Exoplanet Science

The thought that other stars should also have planets orbiting them led scientists to find a way to get closer to these stars using advanced telescopes, and the real revolution began in 1992 with the discovery of the first exoplanet orbiting a pulsar. By 1995, the first exoplanet orbiting a Sun-like star was confirmed, 51 Pegasi b. Today, over 5000 exoplanets have been discovered, and many yet to be discovered.

These planets, especially those in the habitable zone, the region around a star where liquid water can exist, are prime candidates in the search for extraterrestrial life.

What Do We Mean by “Signs of Life”?

In the scientific community, “signs of life” usually refer to bio-signatures, which are measurable indicators of past or present life. These can be:

• Gaseous bio-signatures: Gases like oxygen (O₂), ozone (O₃), methane (CH₄), or combinations that suggest chemical disequilibrium, detectable in a planet’s atmosphere.
• Surface bio-signatures: Features like vegetation red edge spectral reflectance caused by chlorophyll.
• Techno-signatures: Evidence of technological activity, such as artificial light or pollutants.
• Dimethyl Sulfide (DMS): This is a potential game-changer. On Earth, it comes mostly from marine life. It is one of the strongest bio-signature hints ever seen.

A Recent Discovery: Possible Detection of DMS on K2-18b

In 2023, astronomers using the James Webb Space Telescope (JWST) detected possible signs of a molecule called dimethyl sulfide (DMS) in the atmosphere of a distant exoplanet called K2-18b [1]. This molecule is especially interesting because, on Earth, it is produced almost exclusively by biological activity, mainly marine phytoplankton.

K2-18b: is a sub-Neptune-sized exoplanet located about 120 light-years away in the Leo constellation. Its radius is 2.6 times and its mass is 8.6 times that of the mass of Earth. It resides in the habitable zone of its star, and its atmosphere shows signs of water vapor and possibly methane and carbon dioxide molecules important for life as we know it.

You may be wondering how they name exoplanets and why K2-18b; Well! Here, “K2” refers to the K2 space telescope, which was an extension of the Kepler mission. “18” indicates the number of the star in the K2 catalog. The “b” signifies that K2-18b is the second planet found orbiting K2-18, a red dwarf star in the Leo constellation (Singh Rasi). Also, this planet led to the definition of a “hycean planet”, a type of planet that has both abundant liquid water and a hydrogen-enriched atmosphere.

What Makes This Discovery Special?

1. Potential Bio-signature: The presence of DMS, if confirmed, could point to biological processes.
2. Temperate Conditions: K2-18b appears to have moderate temperatures and a water-rich atmosphere.
3. Future Investigations: This is one of the first times scientists have detected such a complex organic molecule on a potentially habitable exoplanet.

Takeaway: Here, it is important to emphasize that this finding is still tentative. The James Webb Space Telescope’s observations require further confirmation, and non-biological sources of dimethyl sulfide (DMS) can not yet be ruled out. This clarification was made by Professor Nikku Madhusudhan, the lead researcher from the University of Cambridge. Some scientists have also proposed abiotic origins for DMS [2]. Nevertheless, Professor Nikku remains hopeful that ongoing research will help clear the uncertainties surrounding the possibility of life on this distant exoplanet.

What’s Next?

Scientist expect to further improve their algorithm to detect the signature of DML in the absorption spectra received in a transient experiment. A greater number of experiments will be conducted to confirm the precise observation of DML, hence life on the planet. Upcoming missions like ESA’s Ariel, NASA’s Habitable Worlds Observatory, and ground-based Extremely Large Telescopes (ELTs) will also help to observe the atmosphere of exoplanets and the possibility of life over there.

As we refine our models and expand our detection capabilities, we may one day answer the age-old question, not just with hypotheses or hope, but with evidence.

1. Madhusudhan, Nikku, Savvas Constantinou, Måns Holmberg, Subhajit Sarkar, Anjali AA Piette, and Julianne I. Moses. “New Constraints on DMS and DMDS in the Atmosphere of K2-18 b from JWST MIRI.” The Astrophysical Journal Letters 983, no. 2 (2025): L40.
2. Hänni, Nora, Kathrin Altwegg, Michael Combi, Stephen A. Fuselier, Johan De Keyser, Niels FW Ligterink, Martin Rubin, and Susanne F. Wampfler. “Evidence for Abiotic Dimethyl Sulfide in Cometary Matter.” The Astrophysical Journal 976, no. 1 (2024): 74.