Nov. 8, 2011 at 10:58 PM ET
After analyzing our capability to detect objects in the solar system, researchers have come to a conclusion that should be fairly obvious: Even if extraterrestrials left something in our solar system like the artifacts we’ve sent out into deep space, we almost certainly wouldn’t know they were there.
"The vastness of space, combined with our limited searches to date, implies that any remote unpiloted exploratory probes of extraterrestrial origin would likely remain untouched," Penn State researchers Jacob Haqq-Misra and Ravi Kumar Kopparapu write in a paper accepted for publication by the journal Acta Astronautica.
The claim that there are plenty of places where alien robots or monoliths could lurk comes as no surprise to Douglas Vakoch, director of interstellar message composition at the California-based SETI Institute. "That's standard wisdom in the field," he told me today.
Our messages to the cosmos
The latest research quantifies just how unexplored different parts of our solar system are, but the bottom line is that we haven't searched the prime areas closely enough — particularly if we're looking for objects ranging from 1 to 10 meters (3 to 33 feet) in size. That's roughly the size range for the human-made objects that are on their way out of the solar system, including the Pioneer and Voyager probes.
Those particular '70s-era spacecraft were equipped with objects that could conceivably tell extraterrestrial civilizations that intelligent entities inhabited at least one planet in our solar system: The Pioneer 10 and 11 probes carried plaques that bore pictures of a human male and female, along with symbols representing our cosmic location. The Voyager spacecraft had "Golden Records," pictogram-bearing phonograph records that could be played to reveal the sights and sounds of Earth.
Haqq-Misra and Kopparapu imply that if the aliens were like us, they wouldn't be able to pick out the Pioneer and Voyager spacecraft, let alone the plaques and the records. "Few if any of the attempts would be capable of detecting a 1 to 10 meter probe," they write.
Even if an alien object were left on Earth, it's not 100 percent certain that it could be found. "The surface of the Earth is one of the few places in the solar system that has been almost completely examined at a spatial resolution of less than 3 feet," the researchers write. Nevertheless, non-terrestrial objects could lurk on the ocean floor, or in the depths of a jungle, or inside a deep cave. There's even a chance that the probe would just look like a rock.
And when you're talking about the whole solar system, the task is analogous to "finding a needle in a thousand-ton haystack," the researchers write.
Signals vs. artifacts
Vakoch said that's why scientists involved in the search of extraterrestrial intelligence, or SETI, tend to focus on radio signals (or laser pulses) rather than physical artifacts. "It's much less energetically expensive," he said. "In a way, it's easier to search for intelligence across the galaxy than it is in our backyard."
Similarly, SETI researchers don't hold out much hope that E.T. will come across our the Pioneer plaques or the Golden Records, much less figure them out. "There's a minuscule chance that any of the things we've sent so far will ever be detected by even the hardiest extraterrestrial civilizations," Vakoch said.
Vakoch observed that the research suggests "one possible response to the Fermi Paradox." Back in 1950, physicist Enrico Fermi and his colleagues discussed the prospects for alien life, and speculated that if intelligent beings could arise in other planetary systems, there should have been enough time for them to visit Earth many times over millions of years. "Where are they?" Fermi is said to have asked.
Haqq-Misra and Kopparapu propose an answer of sorts: "Searches to date of the solar system are sufficiently incomplete that we cannot rule out the possibility that non-terrestrial artifacts are present and may even be observing us," they write.
Maybe there's a cast-off alien plaque sitting just over a hill somewhere on Mars ("We Came in Peace for All Blurxkind"). Or maybe the latest "Transformers" movie had it right after all. What do you think? Feel free to weigh in with your comments below.
More on the alien search:
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