Alien Poop Means We Are Not Alone. But...

Alien Poop Means We Are Not Alone. But Let Me Just Adjust This Model Parameter...

K2-18b and our new age of alien agnosticism

...If you accept the latest evidence at face value, alien life is now arguably the leading hypothesis. And K2-18b joins an ever-growing list of suggestive biosignatures on multiple exoplanets. There’s TOI-270d, sporting not only methane but also carbon disulfide (which on Earth mostly comes from biological processes), along with signs of an out-of-equilibrium atmosphere implying weird conditions we don’t understand… or life. There’s TRAPPIST-1e, another world which will soon be subject to James Webb Space Telescope observations with clear prior predictions about biosignatures from modeling. Even Proxima Centauri b—literally the closest exoplanet to Earth—could possibly have an oxygen atmosphere (which isn’t unique to life, but is suggestive), and at some point in the near future studies will examine its surface reflectance, since any vegetation will leave behind a detectable signature there.

There are now even possible technosignatures of alien life, not just biosignatures. As I’ve written about, researchers have quietly identified 53 stars that are Dyson sphere candidates, detected via excess mid-infrared emissions. They’re just candidates requiring investigation, of course, but the search for Dyson spheres is now firmly in the realm of real science, not fiction. Then there’s ʻOumuamua: noticed back in 2017, it was the first identified interstellar object to wander through our solar system, and was also weird in almost every way, from its thin oblong shape to how it accelerated away. I don’t judge all of this as equally good evidence (ʻOumuamua has multiple natural explanations), but collectively the growing list of biosignatures and technosignatures represents a major change. Alien life is no longer about waiting for evidence, but debating the surprisingly not-crazy evidence we do have...