What if we've been silently observed by an alien civilization since humanity's genesis? A new idea put forth by astronomer Dr. James Benford in a paper published in the Astronomical Journal this week suggests that our search for alien intelligence should focus on the "co-orbital" asteroids that orbit the sun in a similar pattern to Earth. Benford suggests that these asteroids would provide perfect observation decks on which aliens may have stationed robotic probes, laying dormant since ancient times. He argues that these co-orbitals should be a primary target for SETI, the Search for Extraterrestrial Intelligence. He also suggests that if we look at these asteroids and do not find evidence of ancient alien probes than it tells us something else: we're well and truly alone and no one cares about us.
Now that might be a pretty big assumption to make. After all, there's the whole fallacy of thinking that an alien intelligence would come up with the same plans, tactics, and techniques as an Earth-bound descendant of chimpanzees would. But it's clear that Benford is right about one thing at least—if aliens did have a long-term observation strategy, co-orbital asteroids would be perfect staging areas.
Dr. James Benford calls these potential probes "lurkers." They would be small probes that have remained hidden and unnoticed for thousands of years, watching us, or perhaps waiting for a signal to turn on and begin watching us. A news release covering Benford's new paper says:
"They may respond to an intentional signal and may not, depending on unknown alien motivations. Lurkers would likely be robotic, like our own Voyager and New Horizons probes.”
"Co-orbitals" are a recently discovered group of asteroids that orbit the sun at similar rates to Earth, thereby staying at roughly the same distance from our planet. If aliens had stationed probes on these asteroids they would have a constant source of solar energy and and a secure, hidden, and stable place from which to observe us. Regardless if aliens use technology remotely similar to ours or not, the physical laws of the universe would still apply. Everything needs energy, and in the void of space solar energy is probably the best bet regardless of what the probe actually looks like. Benford says that probes hanging out on co-orbitals could possibly sustain themselves for many thousands of years.
Benford says that if we did find an alien probe on one of these co-orbitals we could simply photograph it and send it the photograph with a message saying "we see you." And sure, that's a pretty creepy thing to do, but so is spying on a whole species for all of their evolutionary history. It's only fair.
But if we don't find one, Benford says that it would be strong evidence that we truly are alone. He says:
“If we find nothing there, this gives us a profound result: no one has come to look at the life of the Earth, which has been evident in our atmosphere in spectral lines over interstellar distances for over a billion years.”
But it has to be said, what if they just did something else? Sure co-orbitals would be perfect places to stage an observation from, but many people who have been told there's a perfect way to do something end up doing it a completely different way, to varying degrees of success. Jumping straight to "well if it's not there, in that specific spot, then that means it doesn't exist anywhere else" is pretty ludicrous. That sounds like what I say about my car keys when I'm grumpy in the morning. But that's a problem with looking for alien intelligence. We don't know what it looks like, and we don't know how it thinks. Assuming that it behaves exactly like Earth primates, when there's a whole universe of infinite possibility seems a little bit small minded. But of course, that's coming from someone who is 100% sure his car keys got eaten by a black hole at least three times per week.