There’s no shortage of candidates for the cause of the mass extinctions of prehistory. But experts have found flaws in every one.
Asteroid impact at Chicxulub, Yucatan clearly played a role in the Cretaceous-Tertiary (KT) extinction that wiped out the dinosaurs 65,000,000 years ago, though scientists differ on whether it actually caused the extinction because serious disruptions had begun hundreds of thousands of years before with the basalt flows of the Deccan Traps.1 Some researchers argue that giant basalt lava flows that poisoned the atmosphere and oceans played a central role in all five major extinctions. But no consensus exists on what forces triggered them.
Lurking in the background, however, is a quite plausible cause, one that would have possessed the power to set off the volcanic activity, air pollution, sea level shifts, loss of oxygen in oceans, climate changes, and other phenomena associated with the extinctions. Yet this cause does not seem to have been proposed, and proving or disproving it will require a good deal of investigation. Curiously, nonetheless, a significant body of relevant research has already been carried out in a subject parallel to the extinctions. But that research languishes in a scientific limbo.
The Martian Theory
The new candidate can be termed the Martian Theory of Mass Extinctions (MTME). According to MTME, repeated approaches by Mars to Earth at irregular intervals caused tidal movements in already stressed geological formations, setting off widespread volcanic eruptions and activating mantle heating and plumes that led to hundreds of thousands of years of gargantuan lava flows. Mountainous tsunamis and earthquakes added to the destruction.
Planetary approach, of course, forms a central component of Immanuel Velikovsky’s well-known interpretation of ancient myths, observations, and other evidence for the Bronze Age catastrophes in his Worlds in Collision (1950). The long controversy over Velikovsky’s wide-ranging theory resulted in its rejection by most scientists and its disappearance from scientific publications. However, new evidence and interpretation have emerged that show that the ancients and Velikovsky were right about core tenets of the theory, even though Velikovsky made errors on peripheral subjects.
These core tenets include that Venus, which appeared to have emerged from Jupiter (actually, it was pulled from the outer solar system by Jupiter’s gravity and heated up while passing the gas giant), approached the Earth with a giant comet tail in a 52-year cycle, causing devastating volcanic and seismic activity. Then Venus approached Mars and set Mars on a course toward Earth that in turn caused more chaos.
When one looks at the much earlier mass extinctions from the perspective of this theory, the perception that they and the Bronze Age phenomena could share a common framework seems reasonable.
It helps to follow a related theory that holds that not just Venus but all the terrestrial planets originated in the outer solar system and were at various times pulled by Jupiter’s gravity into the inner solar system (thus explaining why the ancient Greeks thought that Athena—the original Venus—had sprung from the head of Zeus/Jupiter as well as the presence of significant water on Earth and evidence of its earlier presence on Mars, Venus, and the Moon).
As a consequence, the Earth and Mars would have initially had very eccentric orbits. In the course of interactions over billions of years, their orbits gradually became more circular, though the orbit of Mars maintains an eccentricity that oscillates from 0 to 14 percent. According to the ancients and Velikovsky, Venus arrived in the inner solar system much later. So it is not a suspect in the mass extinctions. Mercury is ruled out as a cause of the extinctions because of its presumably much more remote orbit. The Moon is ruled out because of its small size and relatively regular orbit.
This scenario views the Titius-Bode law of the spacing of planetary orbits not as a law but rather as an outcome. In effect, the planets interacted over time, trying one orbit after another until finally they hit upon a stable solution.
Thus the argument of the MTME is that the orbits of Earth and Mars intersected at their extremities, in particular during the period from 600,000,000 to 65,000,000 years ago. At random intervals, the two planets would have close encounters, triggering the mass extinctions on Earth and parallel massive geological activity on Mars (gigantic volcanoes and the extensive uplifted Tharsis region). It seems plausible that the same gravitational force of Earth that lifted the Tharsis region caused the giant rift of the nearby Valles Marineris, though exactly how is not clear. In other words, MTME would account for several of the outstanding features of the surface of Mars. Roughly speaking, the closer the encounter, the greater the extinction on Earth and the geological activity on Mars, so MTME could account for minor extinctions as well, though these might have had other causes.
Since Venus also approached Mars sometime after 1200 B.C. and interacted with it, the resulting changes on the surface of Mars may confound efforts to discern the catastrophic effects on Mars of encounters that caused the five great mass extinctions on Earth millions of years before.
It is possible that the same process of gravitational rifting that created the Valles Marineris also carved out the original Grand Canyon, with its smaller size reflecting the less powerful gravitational pull of Mars on the Earth. The Barrancas del Cobre valleys of northwest Mexico, usually explained as resulting from volcanic activity 30-40,000,000 years ago, might actually have originated at the same time and in the same way.
It is also possible that occasional interactions went much farther back in time and account for the huge Martian outwash channels (from rapidly melted permafrost and release of water from underground reservoirs) and older volcanoes such as Elysium Mons as well. Tectonic activity and weathering on the Earth would have destroyed much of the evidence of early interactions, but clues on Mars could lead to a reinterpretation of early fossil evidence on Earth that would show hitherto unnoticed evidence of extinctions during the first 2 1/2 billion years of life. Clustered dramatic fluctuations in climate and radical drops in photosynthesis, for instance, are characteristic of Slushball Earth episodes and of the five main mass extinctions, so they may share a common Martian approach trigger. Distinct stages in the evolution of Earth systems, including the biological one, could account for the differences between them.
Cyclical approaches of Mars would explain the perception of one researcher that there could have been “serial extra-terrestrial insults” that kept the extinctions going and cut short attempted recoveries.2 Finally, perhaps after a particularly close encounter, the path of the smaller Mars (roughly 1/9 the mass of Earth) would be altered by the interaction with Earth, and Mars would adopt a somewhat different orbit for tens of millions of years. Then mutual gravitational attraction would gradually bring the two planets together again.
Objection #1. In keeping with the Moon’s tiny influence on tidal heating of Earth, Mars would not possess the capacity to induce sufficient heating to melt rocks and initiate the lava flows of flood basalts. But Mars has approximately 9 times the mass of the Moon. Therefore, at the Moon’s current distance from the Earth of 384,000 km, Mars would exert 9 times the force of the Moon. At 38,400 km, Mars would exert 9 x 10 = 90 times the force of the Moon. And at 3,840 km, Mars would exert 90 x 10 = 900 times the force of the Moon.
Objection #2. Even a force hundreds of times the gravitational force of the Moon would not set off a massive flood basalt flow. In regard to the Earth’s lithosphere, some geologists favor the explanation of the flood basalts as triggered by heating and melting of rock in a relatively small zone just outside the edge of a craton and not too deep. The heating and melting then propagate to entrain more rock from beneath the craton to heat up, melt, and flow. Also, the amount of gravitational force (=tidal heating) exerted by Mars necessary to bring the initial rock up to the melting point would not be large because the gravitational pull would “seek out” the point of vulnerability where the existing temperature of the rock (increasing with depth) plus the added tidal heating (according to a gravitational pull gradient diminishing with depth) would first surpass the temperature needed to melt sufficient rock.
This needs to have happened only at a single vulnerable point along a track; the lesser tidal heating in other areas of the Earth would have limited effects. However, in a special case such as the triggering of the giant flood basalts of the Siberian Traps at the Permian-Triassic boundary 251.6 million years ago, there was simultaneous great volcanism in southern China that left layers of ash at Meishan in China. Nonetheless, neither eruption seems to have spread a significant amount of ash around the world because in many other locations the final Permian layer gives way to the first Triassic one without any layer of ash in between.3 In turn, the simultaneity and relative propinquity of the eruptions suggests that they may have shared a trigger mechanism. According to MTME, both locations could lay along the track of Mars as it passed by Earth. In other words, the peculiar regionality of the extinctions matches the constraint of a single track characteristic of the MTME. The track of a solar eclipse provides a rough parallel.
A second possible mechanism would have Mars’ gravitational pull set off seismic activity—a powerful earthquake—that would in turn lead to heating and melting of rock at the point of vulnerability. Or direct heating by tidal friction and indirect heating via a seismic intermediary could have acted together to trigger melting of rock.
Thirdly, an approach of Mars could have triggered a response in the fluid, largely iron outer core that, in turn, would cause a mantle plume that would fuel the eruption of flood basalts.
Whichever of these three mechanisms might have been at work, it may have interacted with other geological phenomena such as subduction. While each of these mechanisms deserves investigation, the more general point is that some such mechanism must have been at work in order to explain the very suggestive evidence on the surface of Mars, which leads to a third objection.
Objection #3. The force exerted by Earth on Mars at such close quarters would have melted the entire surface of Mars, assuming that Mars came close enough to melt a part of the Earth’s lithosphere. This effect, however, would be constricted by tidal locking. Either the great volcanoes or the Tharsis bulge would lock onto Earth during an encounter, and so the greatest force of Earth’s gravity would focus on that point. In turn, the surface of the surrounding area of the northern hemisphere of Mars might indeed melt, but the locking would keep the surface of Mars’ southern hemisphere intact. As Mars rotated upon approaching Earth, whatever part of Mars’ surface would initially come into closest contact with Earth would quickly give way to Mars’ most vulnerable and prominent locking points—the volcanoes and the Tharsis bulge—so that the southern hemisphere would never undergo sustained severe direct gravitational pull.
In other words, during a near miss Mars would have possessed a much greater capacity than the Moon to cause tidal heating on Earth yet would avoid having its entire surface melted by Earth.4
Objection #4. The gravitational pull of Mars would not reach deep enough into the mantle to set off the plume that caused the immense basalt flows of the traps. But American and Russian scientists have elaborated an explanation of an “edge-driven secondary convection” that points to a shallow source.5
Searching for Evidence
How can we test the Martian Theory?
- Studying together the Bronze Age catastrophes and the mass extinctions could shed light on both. For instance, there are good reasons to think that during the Bronze Age catastrophes the Earth, under the influence of Venus’ gravity, turned over four times. Giant tsunamis swept far inland in China and elsewhere. Since Mars exerted a larger gravitational effect during its very close prehistoric encounters, it is likely that the Earth inverted in response, and much more rapidly than the ten-day duration of the Bronze Age inversions, thereby upturning the water column and disrupting circulation patterns. Each prehistoric inversion would have caused tsunamis that dwarfed those of the Bronze Age and would, better than any other reason, have generated the exceptional devastation of the mass extinctions. Evidence of such tsunamis has been mistakenly attributed to bolide impacts.6 Repeated very close approaches of Mars could have caused several inversions in a row, while the rapidity and hence the destructiveness of the inversion could have been related to the closeness of approach, which would explain why the largest five mass extinctions differed in extent.
- We need to seek much better detail on Martian volcanic activity. For instance, pinning down the initial date of a Martian volcano to the date of a mass extinction would constitute telling evidence, and a sequence of matching dates from Martian stratigraphy would be even more persuasive. The double extinctions of Late Devonian and Permian eons, for instance, could be matched by a parallel pattern in Martian volcanoes, and other patterns on Mars may fit the contours and idiosyncrasies of the great mass extinctions on Earth. Meanwhile, Hellas depression at the antipodes of the Tharsis region, while clearly formed by an impact that scattered debris for 4000 km, could conceivably have been deepened, as the most vulnerable part of the antipodes, by the Earth’s gravitational pull on the opposite side of Mars. This would account for its exceptional depth (8200 meters).
- Given the possibility that during some encounters Mars would have come close to the Moon, a search on the Moon also might yield evidence. In particular, the large maria formed by lava flows on the Moon might have in part be caused by early close encounters of the Moon, as well as the Earth, with the Red Planet. The disproportion between their presence on the near side (31.2 % of its surface) and the far side (2.5%) has defied explanation. But a report7 of domes ranging from less than 1 km to more than 6 km, some with steeply sloping sides, in the Compton-Belkovich thorium anomaly on the far side suggests that the gravitational pull of a passing Mars could have uplifted the domes; and it might have caused the lava flows that formed the few maria as well. In other words, pulled by Earth’s gravitational field, Mars tended to pass between Earth and Moon during encounters; but occasionally it presumably passed outside of the Moon. The finding of major spikes in the past 400 million years in the numbers of lunar spherules, some from pyroclastic eruptions, would also be consistent with approaches by Mars.8 Again, the Bronze Age approaches of Venus to Earth could have affected the surface of the Moon as well.
- We need to study the questions of celestial mechanics that the Venus approach theory and the MTME raise.
Why the MTME?
Why should we think that the Martian Theory of Mass Extinctions is the long-sought solution to the mystery of the mass extinctions?
- Close approaches of Mars would have had the requisite power to set off tremendous seismic and volcanic activity, which in turn could entrain the other phenomena associated with extinctions. Possible rapid inversions would add to this picture.
- The MTME fits the irregular, repeated pattern of the mass extinctions.
- The colossal volcanoes and uplifted Tharsis region of Mars are consistent with repeated encounters with Earth, and the time range seems right.
- A body of evidence and theory about the approaches of Venus and Mars in the Bronze and Iron Ages parallels what is known about the mass extinctions.
- Approaches by Mars would perfectly fulfill the apparent criterion of a powerful perpetrator who committed the crime, then disappeared without leaving a single footprint—and then returned to the scene of the crime to commit another and another and another.
- MTME is consistent with the theory and evidence that the terrestrial planets originated in the outer solar system, were pulled by Jupiter’s gravitational field into the inner solar system as quasi-comets, and thus originally had highly eccentric orbits, though Venus and the Earth-Moon system soon lost their eccentricity.
Of course, the MTME requires extensive research and discussion before scientists can arrive at a considered conclusion regarding its merits. Nonetheless, one can see already that it could provide a neat solution to the baffling mystery of what triggered the mass extinctions.9
Kenneth J. Dillon is an historian who writes on science, medicine, and history. See the biosketch at About Us.
Mars has surface features that are not seen on inner planets or moons. These are hemispheric asymmetries, idiosyncratic surface fracturing, localized vulcanism, altitude differences, chains of pits, and the nature of dry river-like channels. Other features include extensive loss of an early atmosphere and liquid water. There is interest in the lower-altitude northern region, with its surface formed after the period of heavy bombardment, as a possible ocean basin. The evidence for this is very sparse: no river deltas, no river networks, little debris at the ends of the catastrophic flow channels. The surface is consistent with the stripping anticipated by a Roche-limit encounter. The low-density Martian moons appear to be unconsolidated material of higher density; they appear to be from low-gravity aggregation of that part of the Martian debris that went into orbit as a short-lived ring. A Roche-limit encounter is invoked as a reasonable hypothesis to explain these features. Earth, Mars’ nearest planetary neighbor, may have provided that encounter. The Roche limit is 2.9 Earth radii.