There's been a LOT of talk about aliens lately.
For the most part, I try not to comment on news stories about UFOs or, as they're more often called these days, "unidentified aerial phenomena" (UAPs) . In fact, I've written about why if you have questions about UAPs, I'm definitely not the one to ask. The short version is that UAPs are aerial phenomena -- things that are seen inside the Earth's atmosphere, usually by people who are also inside the Earth's atmosphere, doing complicated things (like flying fighter jets). Most of my expertise lies in deep space, theoretical physics, and the evolution of the cosmos as a whole. I can assure you that the videos and sightings discussed by UAP folks are things definitely better evaluated by experts in optics, atmospheric physics, and military hardware.
Nonetheless, this week, I've had lots of questions from friends and family about a UAP hearing in Mexico (about which there have been pretty major concerns) and about a report by a NASA committee that concluded that there's really no evidence that UAPs are anything extraterrestrial (but that we should probably keep studying this stuff anyway, just in case they're interesting one way or another). I don't think there's a whole lot more to say about those news items -- from my perspective, I'm pretty sure if there were solid, reliable, intriguing evidence for something really cool (or scary), it would be
completely impossible to hide it, because all the scientists would be far too excited to keep quiet.
But some scientists were excited about possible aliens this month: a JWST result was announced hinting at signs that an exoplanet -- a planet
orbiting another star -- just might have signs of life.
The signs are... ambiguous, at best. The observation consisted of looking at the spectrum of the parent star when the planet was in the way, so the light was filtered through the planet's atmosphere. That allowed scientists to infer the presence of certain chemicals in the atmosphere of the planet, based on patterns in how the light was absorbed. From Hubble observations, we already had data suggesting that this planet, K2-18 b, is in its star's habitable zone and has water vapor in its atmosphere. Intriguing!
The biggest news from the JWST result was that the spectrum is consistent with a planet that has a watery ocean, an atmosphere containing hydrogen, carbon dioxide, and methane (all good signs!), and seems to contain hints of a chemical called dimethyl sulphide (DMS). On Earth, DMS is mostly produced by plankton in the ocean, so a lot of people got excited about the possibility that we are seeing a byproduct of alien life.
There are also reasons to be cautious. The detection of DMS was marginal at best, and just because something is produced by life on Earth, it doesn't mean that it can't be produced by weird geophysics or chemistry somewhere else. As soon as the result was announced, I came across several social media threads and articles from astronomers expressing extreme skepticism about all aspects of the result. Based on everything I've read, it seems we have a long way to go before we can say much at all about this planet's prospect for harboring (possibly microscopic) aliens.
But both the claimed detection and the discussion around it are good illustrations of what it will probably be like if (when?) we eventually do find extraterrestrial life. It probably won't be little green men landing in a field, asking to be taken to our leader. Most likely, the first solid evidence for life on other worlds will be a weird little feature in an exoplanet spectrum indicating a ratio of chemical species we don't expect to find on a lifeless world. There may be conflicting observations (in this case, while Hubble explicitly detected water, JWST, for whatever reason, didn't), and there will certainly be endless arguments, debates, criticisms, and discussions among experts about what kind of chemistry was seen, whether or
not the detection is robust, and what it means if it is.
(Remember when everyone got excited about a detection of phosphine on Venus? That detection was argued endlessly at the time and ultimately not
confirmed in later observations. So it goes.)
All these observations and arguments will be highly technical and take a lot of time, but that's how science works. The technical aspect is because it's just fundamentally hard to do this kind of research, and the arguing is a feature. If a group of scientists ever start actually agreeing on stuff, you can tell the evidence has gotten really compelling.
In any case, if you're really excited about the prospect of alien life, my advice is to pay attention on the exoplanet astronomers, not the UAP reports.
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