“As we improve our understanding of ancient Earth and the history of our solar system, perhaps we may someday uncover evidence that suggests the activity of another technological civilization right here in our neighborhood,” says Andrew Siemion, the director of Berkeley’s SETI Research Center.
Open Question of Astrobiology
One of the open questions of astrobiology is whether there is extant or extinct life elsewhere the Solar System. Astronomer Jason Wright at Penn State says that we are looking for microbial or, at best, unintelligent life, even though technological artifacts might be much easier to find.
The Aliens Before Us –“We are Not the First Technological Civilization” (Or, are We?)
Searches for alien artifacts in the Solar System typically presumes that the origins such artifacts would be from beyond our Solar System, even though life is known to have existed in the Solar System, on Earth, for eons. But if a prior technological, perhaps spacefaring, species ever arose in the Solar System, it might have produced artifacts or other technosignatures that have survived to present day.
Extreme Speculation?
The origins and possible locations for technosignatures of such a prior indigenous technological species might have arisen on ancient Earth or another body, such as a pre-greenhouse Venus or a wet Mars.
“A Red Herring” –The ‘Life-Bearing’ Clouds of Venus
In the case of Venus, the arrival of its global greenhouse and potential resurfacing might have erased all evidence of its existence on the Venusian surface. In the case of Earth, erosion and, ultimately, plate tectonics may have erased most such evidence if the species lived a Gyr, a billion years, ago.
Wright suggests there could have been an explosion in life around the time of or after the Cambrian period, when a sudden wave of complex animals appeared, according to fossil records.
A cosmic catastrophe may have destroyed this early species, erasing all signs it ever existed and “forcing the biosphere to ‘start over’ with the few single-celled species that survived,” Wright writes.
Erased by Shifting Tectonic Plates
We may have already seen technosignatures in geological record, but mistaken them for natural phenomena, Wright said. Or, the evidence may be long gone, erased from the surface by shifting tectonic plates. “The Earth is quite efficient, on cosmic timescales, at destroying evidence of technology on its surface,” he writes in the paper.
“Clues to Alien Life” –Billions of Fragments of Venus May Exist on the Moon
Wright “correctly points out that there has existed ample opportunity for this to have occurred,” says Siemion.
Earth is the only place known to host intelligent life, which makes it a prime target for this kind of search. Life, after all, develops on planets with suitable environmental conditions, and Earth has provided just that.
Other indigenous technosignatures might be expected to be extremely old, limiting the places they might still be found to beneath the surfaces of Mars and the Moon, or in the outer Solar System.
“Technological Civilizations in the Cosmos May Collapse from the Climate Change They Trigger”
Mars in particular may be well mapped by orbiters and rovers, but technological artifacts could be buried underneath its surface.
Cities of Venus
“For all we know, maybe Venus had cities all over it a billion years ago and now they’re gone,” Wright said.
The suggestion that artifacts from another intelligent species may be lying around the solar system is an old one, Wright said, first considered in the literature in the the 1890s.
“Once it felt like we had good maps of everything, once we went to Mars and mapped mars and mapped the moons of Jupiter, it all became a lot less unfamiliar,” Wright said. It makes sense that astronomers now look elsewhere, studying the subsurface oceans of Europa and Enceladus and listening for radio pings around stars light-years away. But the existence of technosignatures from an ancient species somewhere in time, Wright said, remains plausible.
A cosmic catastrophe may have destroyed this early species, erasing all signs it ever existed and “forcing the biosphere to ‘start over’ with the few single-celled species that survived,” Wright observes. We may have already seen technosignatures in geological record, but mistaken them for natural phenomena, Wright said. Or, the evidence may be long gone, erased from the surface by shifting tectonic plates.
“The Earth is quite efficient, on cosmic timescales, at destroying evidence of technology on its surface,” he writes in the paper.
If an “indigenous technological species” once existed somewhere in the solar system, why did they go extinct?
Wright suggests that an asteroid impact that led to mass extinction, a supernova closer than 30 light years, or a lethal burst of gamma rays. Or, perhaps the species, as some do, just died out, leaving behind hints of its history, and some corroded out of existence
The Daily Galaxy via The Atlantic and “Prior Indigenous Technological Species”