Popular media portrayals of extraterrestrials visiting Earth have tended to display the dramatic: giant spaceraft, killer robots, and nefarious aliens. A more realistic scenario is decidedly more mundane, but still undeniably world-shattering: a single, robotic probe, visiting Earth in orbit or landing as a rover.
Back in 1998, Allen Tough, a Professor Emeritus at the University of Toronto and an expert in the Search for Extraterrestrial Intelligence (SETI) before his death in 2012, postulated that there might be alien civilizations in the Milky Way galaxy with the ability to send out hundreds of small, intelligent probes to explore space. His supposition was reasonable. Today, well-funded collaborations like Breakthrough Starshot here on Earth are now actively working toward such an endeavor.
So what if Tough was right, and tens, hundreds, or even thousands of years ago, a far-off alien civilization dispatched dozens of robotic scouts out into the cosmos and one such rover eventually cruised its way to Earth?
What should be humanity's response?
The first step, according to Tough, would be to confirm that the craft really isn't from Earth, perhaps from a secretive government. A smart, skeptical team, ideally composed of scientists from various countries, would need to be recruited to examine the probe. If it's on land, the rover should probably be quarantined at the area it touched down. If it's in space, a robotic or a crewed mission would undoubtedly be required for an up-close look.
Once the probe's authenticity is confirmed, Tough stresses that the finding should be made public worldwide, with all collected data openly shared.
What to do next depends upon the nature of the probe.
According to SETI Senior Astronomer Seth Shostak, we'd want to find out if it's broadcasting any radio signals out into space, and probably block them at least temporarily. Such signals, especially if they are unidirectional, would likely be attempts to communicate with the aliens who sent it. We might not want the probe revealing too much about humanity before we can ascertain its intent.
If the probe's intent is judged to be benign, or even friendly, we'd next want to try to communicate with it. If it's plainly unintelligent, this could take some time. After unblocking its communications, we'd likely have Earth representatives attempt to share basic information, something like mathematical principles, gestures of friendship, or music. We'd then have to wait for the probe's handlers to respond through it. If the craft traveled for a long time, this could take hundreds of years! Shostak isn't sure humans would be able to wait that long – the desire to disassemble the probe and learn from it's technological guts might be too great.
But how would extraterrestrials feel if we took apart their probe? Shostak doesn't think aliens would be too mad. After all, if genial Martians suddenly appeared and messed with Curiosity, NASA engineers would be ecstatic - nothing would increase the space agency's budget more.
It would be more interesting if the probe or rover was artificially intelligent, thus capable of communicating with humans directly. Tough believed that any alien probe sent expressly for long-distance exploration would likely be capable of learning from, and even communicating with, a race it encountered.
"The probe has presumably already monitored our radio and television broadcasts, learned at least one of our languages, and learned about our culture and history," he wrote.
That certainly would be convenient and fascinating! While it's hard to hypothesize on what exactly an intelligent alien probe might tell us, Tough has a good idea about how we should act around it: show respect, avoid violence, speak and act truthfully, and deal with it fairly and honestly.
He also thought that any communication should be attempted with international scientific cooperation as well as openness to the public, aspirations perhaps as unlikely as an alien probe visiting Earth in the first place!