Other scientists who have researched mass extinctions are more measured about the latest findings. “I’m sort of agnostic [about the larger theory],” said Paul Renne, the director of Berkeley Geochronology Center. “But I was really disappointed to see they used an age-database for the craters which is full of outdated information.”

Renne is the author of another new study that focuses on the Chicxulub crater, the massive divot beneath the Yucatán Peninsula that was created by the same impact blamed for the extinction of the dinosaurs. Renne and his colleagues believe that the comet or asteroid that blasted into Earth and made Chicxulub also set off a global chain-reaction of volcanic eruptions that accelerated the end of the dinosaurs. Volcanoes were, they believe, erupting continuously for millions of years. Long enough to make Hawaii’s Kilauea, which has been flowing since 1983, seem laughable. (“Kilauea is nothing,” Renne told me. “Kilauea is a flea.”)

And while Renne is interested in the possibility that volcanism is tied to intervals of mass extinction, that possible connection doesn’t explain what kind of cycles might trigger the awakening of Earth’s most powerful magma systems on a global scale. That’s where theories about galactic periodicity come back into play.

“One of the earliest proponents of a periodic record [of mass extinction] was by a guy named Rich Muller,” Renne said. “He proposed a kind of phenomenological periodicity in which they didn’t really have a mechanism.” In other words, Muller found the 26-million-year pattern of mass extinctions on Earth, but didn’t immediately know what drove the cycle.

The latest findings from Rampino and Caldeira build on the idea that regular comet showers cause intervals of mass extinctions. The showers, the theory goes, are triggered by the movement of the sun and planets through the crowded mid-plane of our galaxy. As the sun crosses that region, it disrupts great clouds of space dust. Those clouds, in turn, throw off the orbit of comets, sending them careening toward Earth.

In another theory, planetary scientists suggested that one region of the solar system in particular, known as the Oort comet cloud, plays a key role in mass extinctions. The Oort cloud is a sprawling region at the border of our solar system that contains trillions of icy bodies. Muller put forth a popular hypothesis in the 1980s that said our sun has a sort of evil twin in the Oort cloud. This hypothetical star, he suggested, has an orbital cycle such that it would perturb its neighboring objects, and send 1 billion of them hurtling toward Earth every 26 million years. The star, a binary to the sun, was nicknamed Nemesis, and playfully referred to as the death star. “The binary star, or Nemesis theory, was an alternate to the Galactic-plane story,” Rampino told me. “But the star was looked for, but never found, so Nemesis theory is out of favor now.”