There are, right now, four ways to search for alien life, ranging from the most passive to the most active.
- Wait for their arrival. Assuming aliens exist, some might be spacefaring and capable of visiting Earth. All we need to do, if we want to explore this option, is to wait.
- Search for signals they’re actively broadcasting right now. If there are intelligent extraterrestrials out there, they could be generating detectable, telltale signatures of their existence. Searching for those signals could reveal them.
- Look for biosignatures directly on other planets. Extraterrestrials that aren’t technologically advanced are likely more common, and if we can uncover their signatures on other worlds through careful and intricate observation, that might reveal extraterrestrial life.
- Look for actual living organisms on worlds we can visit.
If it exists on a world in our Solar System, like Mars or Europa, we’ll finally be sending space probes with the capability of finding those biosignatures. If life exists and has thrived for a long time on a nearby exoplanets, direct imaging or transit spectroscopy could reveal hints or even surefire evidence of that planetary transformation. And if intelligent aliens are trying to contact us, we’re better positioned to pick up those beacons than ever before.