On New Year’s Eve 2023, amid appearances by Joss Stone and Rod Steward on Jools Holland’s holiday ‘Musical Hootenanny’, a major 2024 revelation was alluded to: soon, we might learn that we aren’t alone in the universe.
During a segment on the BBC TV program, British space scientist Dame Maggie Aderin-Pocock was asked by Holland what astronomers might expect to learn in 2024, to which the astronomer offered a tantalizing prediction.
“I think we’re going to discover alien life,” Dr. Aderin-Pocock said.
Pocock wasn’t alone in confidently asserting that the answer to one of humankind’s greatest questions might legitimately soon be on the horizon. Similar comments were made around that time by other leading astronomers in the UK, all of which appeared to point to the publication of a scientific paper sometime in 2024 that would present the strongest evidence yet for the existence of alien life on some distant exoplanet far from Earth.
The insinuations that the discovery of alien life could be imminent all followed news from earlier that year, where NASA revealed that the James Webb Space Telescope had detected carbon-bearing molecules, including methane and carbon dioxide, on the exoplanet K2-18 b.
“Webb’s discovery adds to recent studies suggesting that K2-18 b could be a Hycean exoplanet,” NASA reported at the time, “one which has the potential to possess a hydrogen-rich atmosphere and a water ocean-covered surface.” Of particular significance was the apparent detection of dimethyl sulfide on the exoplanet, which astronomers recognize as a potential indicator of life.
“On Earth, this is only produced by life,” NASA reported of the discovery.
That all changed a bit later in 2024 however, with the publication of a study by researchers at UC Riverside that scrutinized whether this potential biosignature gas could indeed accumulate to detectable levels on K2-18b. According to the UC Riverside team, the Webb findings fell short of offering conclusive proof of life on the exoplanet, though it did not rule out the possibility that advancements in detection capabilities might help to confirm such a discovery in the future.
On Earth, dimethyl sulfide (DMS) is generally produced by ocean phytoplankton, which gives rise to the primary source of airborne sulfur on our planet. From its position 120 light-years from Earth, K2-18b stands out among exoplanets for its potential habitability, especially since the planet has several similarities to ours. These include that it receives a similar amount of solar radiation without atmospheric interference, and that it maintains a temperature comparable to Earth’s.
Currently, there is ongoing speculation about oceans comprised of water that may exist under K2-18 b’s hydrogen-dominated atmosphere, all of which suggests it may be what astronomers call a “Hycean” world, where the promising pairing of a hydrogen atmosphere with its water oceans could all further strengthen the chances of life existing there.
Nonetheless, the UC Riverside team’s computer modeling produced earlier this year generated simulations of the environment on the exoplanet that determined it was unlikely the Webb data conclusively indicated the presence of DMS.
“The signal strongly overlaps with methane, and we think that picking out DMS from methane is beyond this instrument’s capability,” said Shang-Min Tsai, a co-author of the UC Riverside team’s study.
While their findings challenged the idea that a strong biosignature had been discovered at the time, notably, the researchers still did not rule out the possibility of DMS accumulating to detectable levels on K2-18b. For this to occur though, any prospective life forms inhabiting K2-18 b would be required to produce 20 times more DMS than is currently present on Earth.
The team’s findings helped to illustrate the complexities of detecting life on exoplanets, particularly given the fact that physical sampling is impossible, and must rely on analysis of atmospheric data from dozens of light years away. However, they also point to some promising potentials.
This year, the Webb telescope was expected to deploy its sensitive instrumentation in further observations of K2-18 b by the end of 2024. Whatever additional data Webb obtains in its ongoing observations could allow for more definitive determinations of whether DMS exists on K2-18b, potentially offering a crucial step forward in the search for extraterrestrial life.
So could 2025 be the year that we finally unveil the best evidence for the existence of alien life that scientists have seen to date? Although nothing is certain, we can already concede that with the help of Webb’s sensitive instruments, astronomers are closer than they have ever been at any time to making such a discovery, although exactly what that could entail remains in question.
“The best biosignatures on an exoplanet may differ significantly from those we find most abundant on Earth today,” explained UCR astrobiologist Eddie Schwieterman, a senior author of the UC Riverside team’s study published earlier this year. “On a planet with a hydrogen-rich atmosphere, we may be more likely to find DMS made by life instead of oxygen made by plants and bacteria as on Earth.”
In other words, a conclusive determination of the presence of DMS in K2-18 b’s atmosphere could reveal a lot about any life that may exist there, as well as the habitat in which it thrives.
For researchers like Shang-Min Tsai, that’s all part of the excitement of the search.
“Why do we keep exploring the cosmos for signs of life?” Tsai reflected. “Imagine you’re camping in Joshua Tree at night, and you hear something.”
“Your instinct is to shine a light to see what’s out there.”
“That’s what we’re doing too, in a way,” Tsai said.
Micah Hanks is the Editor-in-Chief and Co-Founder of The Debrief. He can be reached by email at micah@thedebrief.org. Follow his work at micahhanks.com and on X: @MicahHanks.