I’ve been looking forward to this for many years now: we’ve discovered thousands of exoplanets out there, and now we may have discovered our very first exomoon!
There are a handful of moons in our own Solar System that may be home to alien life, so if we can start observing and studying exomoons, in addition to exoplanets, that greatly expands the number of places we can search for alien life and greatly increases the chance that we might find something.
However, exomoons may also pose a serious problem for astrobiologists. You see, one of the things astrobiologists are looking for are planets with atmospheres in a state of “chemical disequilibrium.” For example, chemicals like oxygen and methane should react with each other and thus remove each other from the atmosphere. The only way those two chemicals can coexist long term is if some ongoing process (like biological activity) is constantly replenishing them.
But imagine an exoplanet with an oxygen-rich atmosphere and an exomoon with a methane-rich atmosphere. From here on Earth, that planet-moon system could easily be mistaken for a single exoplanet, with the two separate atmospheres appearing to be one atmosphere in that much coveted state of disequilibrium.
In this paper—a paper which describes its results as “inconvenient, yet unavoidable”—this is referred to as the exomoon false-positive scenario, but I’m calling it the trickster moon problem, because someday some undetected exomoon might trick us into thinking we’ve discovered alien life when we haven’t.
The good news is that we may have already detected one exomoon, so in time we should get better at detecting others. But as that “inconvenient yet unavoidable” paper warns, it may be decades (at least) before we can reliably tell which exoplanets do or do not have moons. Until then, fellow space explorers, beware of those trickster moons!