Hopes of finding aliens in 2025 were high, but quickly faded

The search for life outside our solar system intensified this year when scientists reported a puzzling signal from an exoplanet of a molecule known to be produced exclusively by life on Earth. Those hopes were quickly dashed when other teams failed to confirm the discovery, but the resulting vigorous debate was a good learning process for would-be alien observers, exoplanet researchers say.

In April, Nico Madhusudan He and his colleagues at the University of Cambridge announced in a press conference that they had seen “the first hints… of an alien world that may be inhabited.” These hints came from K2-18b, a planet about eight times Earth’s mass, 124 light-years away and located in the habitable zone of its star, which they observed using the James Webb Space Telescope (JWST).

Infrared light from K2-18b indicates that its atmosphere may contain a molecule called dimethyl sulfide (DMS), which on Earth is produced only by living organisms, especially marine phytoplankton.

The news predictably caused a stir among the world’s media and scientific communities. But alongside the excitement, many researchers also urged caution. They said the DMS signal was very weak, and would require several additional observations and analysis to confirm.

Now, after months of additional observations and careful analysis, most astronomers agree that we cannot say that DMS, or anything resembling a biomolecule, is present in K2-18b’s atmosphere, and if so, we would not currently be able to detect it. “The only things we know for sure are the presence of methane and carbon dioxide in the atmosphere of this planet,” he says. Louis Wilbanks At Arizona State University.

Wilbanks says the claim that we may have seen extraterrestrial life was premature. “It’s been shown time and time again that it’s not accurate or true,” Wilbanks says. “New observations show that the presence of these gases does not exist.”

However, the spike in data originally attributed to DMS still requires explanation, he says Jake Taylor At Oxford University. “There’s this bump there. It’s physical. We see it. We don’t know what the explanation is right now.”

Taylor says that finding out what molecule is causing the rise will require more observations of the planet, which are being planned with the James Webb Space Telescope for next year. Scientists can only measure what is in the planet’s atmosphere by using the starlight that passes through it when the planet moves in front of its host star, which happens four times every Earth year.

For all the controversy surrounding this disputed discovery, it has led to some positives, Taylor says. “It’s been a really good learning process for the exoplanetary community as a whole,” he says. “We’re now back to the drawing board in terms of what definitions we should use for different statistical methods. It’s been really useful for us.”

“It helps us learn how to realign our expectations,” Wilbanks says. “This is a lesson that if you have to manipulate numbers to claim something exists, it’s a real challenge. Someone much smarter than me said there are lies and damned lies and statistics. Everything to do with DMS falls into that category.”

Secrets of the Universe: Cheshire, England

Spend a weekend with some of the brightest minds in science, as you explore the secrets of the universe on an exciting program that includes a trip to see the famous Lovell Telescope.