As we begin a new year, it seems appropriate to think about big topics. And what could be bigger than asking what observations might count as evidence of intelligent alien beings?
The question is triggered by Harvard astronomer Avi Loeb’s forthcoming book Extraterrestrial: The First Sign of Intelligent Life Beyond Earth, as well as the last big science story of 2020, about a mysterious radio astronomy observation known as Breakthrough Listen Candidate 1, the first candidate for an artificial extraterrestrial signal found by the Breakthrough Listen project, the most thorough SETI search ever undertaken.
Let’s start with BLC1, first reported by The Guardian and later picked up by Scientific American and other publications. The detected radio signal had a frequency of about 982 MHz and varied slightly in frequency, which makes it less likely to be a “false positive” emanating from Earth’s surface. It was detected during 30 hours of observation with the Parkes Observatory in Australia in April and May 2019. But it hasn’t been heard again. The signal apparently was coming from the direction of Proxima Centauri, the closest star system to our own. That system has one known exoplanet, but it is likely not habitable due to strong solar flares emitted from the host star.
It’s possible that the signal originated from a greater distance, behind Proxima Centauri. Or, much more mundane, it may have come from one of our own satellites that happened to be passing in front of Proxima Centauri at the time. BLC1 reminds me of the famous Wow! signal of the 1970s that also stirred up a lot of excitement and sparked many different hypotheses. Unfortunately, if a signal like Wow! or BLC1 is never repeated, there’s not much you can do to figure out its source.
Avi Loeb was one of the first scientists to speculate that ʻOumuamua, the first object seen to enter our Solar System from interstellar space, might be an extraterrestrial spacecraft. He pointed to the object’s unusual shape and noted that it was “shiny,” with a motion indicating that something other than simple gravitation might be propelling it. It will be interesting to see if his book offers additional arguments that the object might be artificial rather than an asteroid. Unfortunately, as with the radio signals, any follow-up studies are not likely to provide further insights, because ʻOumuamua is too far away now.
There’s a similar problem with studying Fast Radio Bursts (FRB), which some scientists have suggested may be artificial in nature. Personally, I think they are much more likely to have a natural origin, maybe similar to pulsars. Either way, because they appear to originate from outside our galaxy, further investigations are hampered by their great distance.
Then there’s the UFO phenomenon—or rather, Unidentified Aerial Phenomena (UAP), a term that has less baggage and sounds more neutral. I’m the first to admit that scientists are often a bit arrogant and too quick to dismiss eyewitness reports of lay people or even the military. The main problem for us scientists—when considering the less than 10 percent of these observations that are truly puzzling—is that the scientific method relies heavily on repeatable experiments. And that doesn’t work well for UAPs. Still, I think we need to investigate these observations, or some of them at least, as they may lead to new insights about still unknown natural and atmospheric phenomena. That’s true no matter where one stands on the view that a fraction of them might be extraterrestrial spacecraft.
That brings us to the claims that certain structures on other planets or moons in our Solar System are artificial, or are fossils of higher life forms. I receive a lot of these, but I don’t find them convincing at all. As a trained geologist, I have seen a lot of strange rock structures that resemble animals or artificial constructions.
Having said that, there is one such case that still puzzles me—one of the images taken by the NEAR Shoemaker mission of the asteroid Eros. One object in that image does not look like a rock to me, although mission scientists interpreted it as a boulder. The object is highly reflective, which in places such as Earth or Ceres would not be unexpected. But there is no reason why there should be salt—at least not this amount—on an asteroid such as Eros. The object is rectangular, and again, rocks shaped like that are not uncommon on Earth, mostly because of weathering processes. Basalt columns on our own planet also have very distinct geometric features that from some viewpoints could appear rectangular. But neither kind of rock would be expected on a small, airless asteroid.
The main problem, as often happens, is that no higher resolution images are available. And what looks like an artificial shape at low resolution could turn out to be an oddly shaped boulder at higher resolution after all. What we need, then, is for somebody to fund a cubesat mission to Eros that can return better pictures. Any takers?