A Scientific Revolution by Push Notification

Few forms of media can still grab the general public’s lapels and say, “The world has changed in an important way, and you should know about it, now” like a push notification from The New York Times. On Wednesday evening, a particularly enticing one from the Times flashed across millions of lock screens. “Astronomers detected a possible signature of life on a planet orbiting a star 120 light-years away,” it read. Soon after, The Washington Post followed up with a notification of its own, using similar language about a possible sign of life found on a distant planet called K2-18b.

The word possible is doing load-bearing—if not Atlas-like—work in these headlines: It is indeed “possible” that a team of astronomers led by Nikku Madhusudhan, a professor at the University of Cambridge, has found a “sign of life,” but only if a whole daisy chain of other possibilities turn out to be actualities. Despite these contingencies, Madhusudhan is quoted in the Times describing this moment—and, by implication, his own work—as “revolutionary.” But when I spoke with other scientists in the field, they were much more circumspect. Sara Seager, a professor at MIT who was once Madhusudhan’s graduate adviser, told me that when it comes to K2-18b, “enthusiasm is outpacing evidence.”

When you read that astronomers have detected possible signs of life on another planet, you might picture them all hunched over a blurry image of K2-18b, zooming in to the planet’s fine details. But no one has ever seen K2-18b in the round; we only know it’s there because its host star dims at regular intervals when the planet passes in front of it. Madhusudhan and his team used the James Webb Space Telescope to collect light from K2-18b’s host star during one of these transits by the planet. A tiny fraction of the light they collected shone directly through the planet’s atmosphere, and that light carried a record of the molecules that it encountered there all the way to the Webb. According to Madhusudhan and his team, one of the molecules that K2-18b’s atmosphere contained was dimethyl sulfide. On Earth, dimethyl sulfide is produced only by living organisms, and not just any organisms: It comes from algae, precisely the kind of life you might expect to find on a planet that is covered in warm oceans, as the team believes K2-18b to be.

It’s worth pausing to say that astronomers’ ability to tease these chemical records out of starlight is nothing short of miraculous. But it is tedious work, and not at all straightforward. (“Gas-phase photochemistry is complex shit,” one astronomer texted me.) The details are too technical to get into here, but the important thing to know is that Madhusudhan and his team did not directly detect dimethyl sulfide. The chemical is only one of several that could be responsible for the signal they found. And although it’s the most likely one according to their models, others disagree.

When I spoke with the astronomer Mercedes López-Morales, she noted that “revolutionary” discoveries in astronomy usually have a different publicity profile than this one. López-Morales is the associate director of the Space Telescope Science Institute, which operates the Webb Telescope on behalf of NASA, the European Space Agency, and the Canadian Space Agency. She pointed out that none of those agencies saw fit to send out so much as a press release about the finding, even though the work was carried out with their telescope. The only major press release came from the University of Cambridge, where Madhusudhan works. It touted the findings as the “strongest hints yet” of life outside the solar system. López-Morales thought this was overstated. If the result had been that solid, “I guarantee that we would have had the White House announcing this,” she said. (Madhusudhan did not respond to a request for comment.)

Even if the detection of dimethyl sulfide on K2-18b were to eventually prove out to the entire field’s satisfaction, its presence is not necessarily a bankable sign of life. Last year, the chemical was observed  in the dead, icy spray of a comet. Whatever dimethyl sulfide’s organic origins might be on Earth, the universe, in all its creativity, is clearly capable of making it without the help of organisms. “If you really want to convince yourself that you’ve detected life, you probably want to see clusters of these biosignatures”—which is to say, other chemicals associated with life—David Kipping, an astronomer at Columbia University, told me. “And you want to have much more contextual information about the type of planet.”

We don’t have much contextual information about K2-18b at all. We don’t even know what kind of planet it is. When I asked López-Morales what we can say about K2-18b that is totally certain, she paused for a long while and then said, “We know there is a planet there; we know that.” Much else is a total mystery, or heavily contested. Madhusudhan pictures a “Hycean” world—wrapped in hydrogen, its surface hidden beneath a global ocean. Another group, studying the same data record, sketches a very different scene: a magma‑ocean hellscape, sterilized by heat. When I asked Michael Wong, an astrobiologist at the Carnegie Institution for Science, if this finding had, at the very least, made K2-18b the most interesting planet on which to look for life, he wouldn’t even go that far: “I’m not quite ready to say that.”

That scientists would want to generate excitement about their research among the general public is understandable. Many of them are funded by taxpayers, after all, and right now research budgets are being slashed, and future observatories are threatened with cancellation. But hype carries its own dangers. Several astronomers I spoke with for this story told me that friends and family had besieged them with text messages when the news broke. Judging by the volume of messages that I, too, received on Wednesday night, a great many people interpreted the Times’ push notification as announcing an epochal cosmic discovery. By the time I woke up yesterday morning, a backlash had already started brewing among scientists on Bluesky, and elsewhere. Ignas Snellen, an astronomer based in the Netherlands, told a reporter at the Dutch newspaper de Volkskrant that Madhusudhan’s framing of the research is “irresponsible nonsense.”

López-Morales worries that there could be a boy-who-cried-wolf effect. After seeing so many previous findings walked back, or dramatically qualified, people won’t believe a genuinely revolutionary discovery when it comes along. “We will one day find life on another planet,” López-Morales said. “That’s what so many of us are working towards. Statistically, with the number of galaxies and stars that are out there, I cannot imagine that there won’t be life elsewhere. But we’re not there yet.” If and when that push notification does light up our lock screens, it would be a shame if members of a jaded public decide to simply swipe it away.