Life on Earth clawed its way toward complexity through a series of near-death experiences.
For billions of years, life on Earth has survived not merely by thriving, but by enduring resets it never saw coming. A researcher in Rome now proposes that some of Earth's greatest extinctions were not caused by direct cosmic impacts, but by the gravitational tides of passing planetary-mass objects — forces capable of triggering tsunamis, volcanic eruptions, and climate collapse simultaneously. The hypothesis, emerging from the study of the Permian-Triassic extinction and fossil coral records, invites us to reconsider how fragile the thread of complex life truly is, and how vast and restless the solar system remains.
- The Permian-Triassic extinction wiped out up to 95 percent of all species 251 million years ago, yet no impact crater or iridium signature has ever been found to explain it.
- Physicist Daniele Fargion argues that a passing dwarf planet or planetary-mass object need not strike Earth directly — its gravitational tidal pull alone could simultaneously trigger megatsunami, volcanic eruptions, sea-level shifts, and asteroid showers.
- Fossil corals from the Devonian period show an abrupt, unexplained change in Earth's rotation rate, which Fargion interprets as evidence of a gravitational flyby that nudged the Moon outward and reshaped the planet's surface.
- The outer solar system harbors thousands — possibly tens of thousands — of dwarf planets on elliptical orbits, meaning such flybys are not ancient anomalies but recurring features of Earth's astrophysical environment.
- If the threat is real and ongoing, humanity's survival would depend on early detection systems scanning the outer solar system and the construction of high-altitude refuges capable of enduring years of global tidal catastrophe.
Life on Earth has never been guaranteed. It has survived by enduring catastrophes it could not anticipate, each one a violent reset imposed by forces operating at scales far beyond the biosphere. The dinosaurs fell to the Chicxulub impactor — that story is familiar. But other extinctions have left quieter, more ambiguous marks in the rock, and a researcher at Rome University is now proposing a mechanism that could explain them.
Daniele Fargion, presenting at a conference in Palermo in June 2025, argues that gravitational tidal forces from passing planetary-mass objects may have triggered Earth's major extinction events. The outer solar system harbors thousands of dwarf planets on elliptical orbits that occasionally send them toward the inner planets. When such an object passes near Earth, Fargion contends, it need not make direct contact. The tidal forces alone could generate continent-spanning waves, trigger volcanic eruptions through deep tidal heating, shift sea levels, and scatter asteroids into collision courses with Earth — all at once.
The Permian-Triassic extinction, which erased between 80 and 95 percent of all species 251 million years ago, is the hypothesis's most compelling test case. No crater has been dated to that period. No iridium anomaly marks the boundary. Volcanic eruptions and sea-level changes have each been proposed, but neither alone accounts for the scale of the event. Fargion suggests a gravitational flyby could have triggered all of these phenomena in cascade, producing a destruction no single mechanism could replicate.
Supporting evidence may be encoded in fossil corals, which preserve Earth's ancient rotation rate in their daily growth rings. Near the end of the Devonian period, roughly 375 million years ago, that rate shifted abruptly — days were lengthening far faster than the Moon's gradual tidal drag could explain. A passing object's gravitational pull, Fargion argues, could have nudged the Moon outward suddenly, matching the fossil record while simultaneously generating years-long tsunamis and interior heating sufficient to drive massive volcanism.
The solar system itself shows signs of such encounters. Uranus tilts on its side. Triton appears to be a captured Kuiper Belt object. The Late Heavy Bombardment may have been gravitationally triggered. If such visitations shaped the outer planets, it would be remarkable if Earth alone were spared. The data from ancient events remains fragmentary, but the pattern is suggestive.
Should such objects pose a continuing threat, Fargion argues humanity would need persistent surveillance of the outer solar system and, in the most extreme scenarios, high-altitude refuges where people and other species might outlast years of global tidal inundation. He notes, with quiet gravity, that the silence of the cosmos — the absence of contact with advanced civilizations — may itself reflect how often life is interrupted before it can reach out.
We are here by accident. Life on Earth clawed its way toward complexity through a series of near-death experiences, each one a reset button pressed by forces beyond any creature's control. The dinosaurs fell to a space rock 64 million years ago—that story is well known, the Chicxulub impact that cleared the stage for mammals to inherit the world. But there may have been quieter catastrophes, subtler mechanisms of extinction that left fewer obvious fingerprints in the rock.
Daniele Fargion, a research professor at Rome University and the Osservatorio Astronomico di Capodimonte in Naples, has proposed that gravitational tides from passing planetary-mass objects could have triggered Earth's major extinction events. The idea emerged in a conference paper presented in Palermo in June 2025, now circulating on the arXiv preprint server. It's a hypothesis that takes seriously the population of dwarf planets known to orbit in the outer solar system—thousands or tens of thousands of them, on elliptical paths that occasionally send them careening toward the inner planets.
When such an object passes near Earth, Fargion argues, the gravitational pull would not need to strike a direct blow. Instead, the tidal forces alone could reshape the planet's surface and interior. Giant waves would sweep across oceans. Volcanic eruptions would erupt from the crust, triggered by tidal heating deep underground. The climate would lurch. Sea levels would shift. Meteor showers would rain down as the passing object's gravity scattered asteroids and comets into collision courses with Earth. The geological record shows that Earth's major extinctions correlate with exactly these kinds of upheavals—climate shifts, volcanic episodes, meteorite impacts, and sea regressions all clustered together in time. But pinpointing which caused which has proven difficult.
Consider the Permian-Triassic extinction, which occurred 251 million years ago and remains the most severe extinction event in Earth's history. Between 80 and 95 percent of all species vanished. Yet there is no iridium anomaly in the rock, no crater dated to that time. The smoking gun of an impact simply does not exist. Volcanic eruptions alone cannot explain it. Sea level changes alone cannot explain it. Fargion proposes that a passing planetary-mass object could have triggered all of these phenomena simultaneously, creating a cascade of destruction that no single mechanism could produce.
Evidence for such flybys may already be written into Earth's own geometry. Fossil corals preserve a record of Earth's rotation rate, encoded in the number of daily growth rings within each annual cycle. At the end of the Devonian period, roughly 375 million years ago, that rate of change shifted abruptly. The days were lengthening—a process normally caused by the moon's tidal drag on Earth's rotation, which happens gradually over millions of years. But this change was sudden. A collision would have been instantaneous and catastrophic. A tidal pull from a passing object, however, could have nudged the moon outward in a way that matches the fossil record. The same tidal forces that moved the moon would have generated tsunamis lasting years, deformed the crust, and heated the planet's interior enough to trigger massive volcanic eruptions.
The solar system itself bears the scars of such encounters. Uranus spins on its side, likely knocked askew by a collision with a planetary-mass object. Triton, Neptune's largest moon, appears to be a captured object from the Kuiper Belt. The Late Heavy Bombardment, a period of intense asteroid impacts early in solar system history, may have been triggered by gravitational perturbations from a passing planet. It would be strange if Earth alone escaped such visitations. Jupiter, Fargion calculates, has suffered roughly 16 collisions with objects of half an Earth's mass throughout its history. The dwarf planet population 4 billion years ago was likely far more massive than it is today.
The challenge is that these events occurred so long ago that precise estimates remain elusive. How many flybys occurred? How massive were the objects? The data is fragmentary. Yet the hypothesis offers an explanation for the correlation between multiple extinction mechanisms that have puzzled scientists for decades. If planetary-mass objects visited the inner solar system in the past, they could visit again. Fargion suggests that humanity's defense would require constant surveillance of the outer solar system to detect approaching objects early, and—if one were truly massive—the construction of high-altitude refuges on mountaintops where some fraction of humanity and other species might survive the years of global tidal waves that would follow. The alternative explanation for why we have not yet encountered advanced alien civilizations, he notes, may be that life itself is fragile, repeatedly reset by astrophysical catastrophes that leave younger worlds in their wake.
Citas Notables
Tidal effects of planetary-mass objects passing near Earth could have caused all of these extinctions and can explain the complex geological records of major biological mass extinctions.— Daniele Fargion, Rome University
Life is unstable and short. Astrophysical tidal extinctions could more rarely cancel any advanced civilization, making a life reset toward a lower, primordial, silent level.— Daniele Fargion, on the Fermi Paradox
La Conversación del Hearth Otra perspectiva de la historia
Why should we take this idea seriously when we already have the impact theory to explain extinctions?
Because the impact theory doesn't explain all of them. The dinosaur extinction has the iridium layer, the crater—it's airtight. But the Permian-Triassic extinction, which killed 95 percent of species, has no impact signature at all. Fargion is saying that a passing planet could trigger volcanic eruptions, tsunamis, and meteor showers all at once, which matches what we actually see in the geological record.
So you're saying a planet could pass by Earth without hitting it and still cause an extinction?
Exactly. The gravitational pull alone would be enough. It would stretch the crust, heat the interior, move the moon, generate waves that persist for years. You don't need a collision. You just need something massive enough passing close enough.
How close is close?
That's one of the things we can't calculate precisely yet. But we know it happened in the past because the evidence is there—the sudden shift in Earth's rotation rate recorded in fossil corals, the tilted axes of other planets, the captured moons. The solar system is full of these signatures.
If this happened before, couldn't it happen again?
Yes. That's why Fargion is arguing for detection systems and mountain refuges. If a planetary-mass object is coming, we'd need years of warning. And if it's truly massive, there's not much we can do except survive it.
That sounds apocalyptic.
It is. But it's also rare. These events are separated by tens of millions of years. The real point is that life on Earth has survived them before. We're here because something always survives, and then evolution starts again.