A team of researchers led by Indian-origin astrophysicist Dr. Nikku Madhusudhan has claimed to have found the strongest indication yet of extraterrestrial life, this time on K2-18b, a massive exoplanet located 120 light-years away from Earth.
Dr. Madhusudhan, from the University of Cambridge, and his team analysed the exoplanet's atmosphere, uncovering an abundance of a molecule typically associated with life on Earth – dimethyl sulfide, which marine algae produce. The discovery was made using the James Webb Space Telescope.
"It is in no one's interest to claim prematurely that we have detected life," Dr. Madhusudhan remarked in a press conference on Tuesday. However, he went on to say that the best explanation for their findings is that K2-18b is likely covered with a warm ocean, potentially teeming with life.
"This is a revolutionary moment," Dr. Madhusudhan stated. "It's the first time humanity has seen potential biosignatures on a habitable planet."
The study, published in Astrophysical Journal Letters, has been met with cautious excitement. Other experts in the field, while acknowledging the significance of the discovery, have urged restraint.
"It's not nothing," said Stephen Schmidt, a planetary scientist at Johns Hopkins University. "It's a hint. But we cannot conclude it's habitable yet."
Canadian astronomers first discovered K2-18b in 2017 using ground-based telescopes. The planet, a sub-Neptune, is much larger than the rocky planets in our inner solar system but smaller than Neptune itself.
Dr. Madhusudhan and his team had earlier proposed that planets of this type, dubbed "Hycean" worlds, could harbour warm oceans of water beneath thick hydrogen-rich atmospheres. This hypothesis was further bolstered by their findings on K2-18b, which showed evidence of several molecules consistent with their model for Hycean planets.
In 2023, the team detected faint hints of dimethyl sulfide, a molecule associated with life. When the Webb telescope revisited the planet’s atmosphere, the signal of dimethyl sulfide became even stronger, alongside a similar compound, dimethyl disulfide.
"This is a shock to the system," Dr. Madhusudhan said. "We spent an enormous amount of time just trying to get rid of the signal." Despite numerous attempts, the signal remained.
The detection suggests that K2-18b may have a substantial amount of dimethyl sulfide in its atmosphere, far more than is found on Earth, hinting at a possible ocean full of life. However, researchers remain cautious, stressing that more data and further studies are needed to determine whether K2-18b is truly habitable.
One question still to be resolved is whether the planet's conditions are as conducive to life as the researchers suggest. Some scientists, like Christopher Glein, have raised the possibility that K2-18b could instead be a massive rock with a scorching hydrogen atmosphere, not a watery world.
Researchers are awaiting further data from the Webb telescope to deepen their understanding of the planet. Although scientists are enthusiastic, they acknowledge that the search for extraterrestrial life is likely to be a slow and gradual process.
"We’re just starting to understand the nature of these exotic worlds," said Matthew Nixon, a planetary scientist at the University of Maryland. "It’s important to remember that we’re just starting to scratch the surface of what K2-18b might be."
As NASA develops more advanced telescopes, future studies may bring scientists closer to answering whether K2-18b, or other distant planets, could harbour life. Despite the slow pace, the research opens exciting possibilities for the future of astrobiology.
“I’m not screaming, 'aliens!’” said Nikole Lewis, an exoplanetary scientist at Cornell University. “But I always reserve my right to scream 'aliens!’”
However, concerns about the future of space exploration remain, with some scientists, like Joshua Krissansen-Totton, worried that funding cuts could halt progress in the search for extraterrestrial life.
The Trump administration is reportedly planning to reduce NASA's science budget by half, which would impact future astrobiology projects. "If that happens, the search for life elsewhere would basically stop," Krissansen-Totton said.
About Dr. Nikku Madhusudhan
Dr. Nikku Madhusudhan is an Indian-origin astrophysicist and professor at the University of Cambridge's Institute of Astronomy. His pioneering work in exoplanetary science has significantly advanced our understanding of planets beyond our solar system.
Academic background and career
Dr. Madhusudhan completed his B.Tech. at the Indian Institute of Technology (IIT) Varanasi, followed by an M.S. and Ph.D. in Astrophysics from the Massachusetts Institute of Technology (MIT), where he worked under the guidance of renowned astrophysicist Sara Seager.
His doctoral research focused on developing atmospheric retrieval techniques to analyze the compositions of exoplanet atmospheres.
After his Ph.D., he held postdoctoral positions at MIT, Princeton University, and Yale University. In 2017, he joined the University of Cambridge as a faculty member and is currently a Professor of Astrophysics and Exoplanetary Science.
Scientific contributions
Dr. Madhusudhan is best known for coining the term "Hycean planet" to describe a class of exoplanets that feature a hydrogen-rich atmosphere and a subsurface ocean, potentially offering environments conducive to life. His research employs advanced radiative transfer models and atmospheric retrieval methods to study the chemical compositions and habitability of exoplanets.
In 2023, he led a team that detected dimethyl sulfide (DMS) in the atmosphere of exoplanet K2-18b, located 120 light-years from Earth. On Earth, DMS is primarily produced by marine life, suggesting the potential for biological activity on K2-18b.
Awards and recognition
Dr. Madhusudhan's work has earned him several accolades, including:
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IUPAP Young Scientist Medal in Astrophysics (2016)
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ASI Vainu Bappu Gold Medal (2014)
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EAS MERAC Prize in Theoretical Astrophysics (2019)
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