Did Dark Matter Kill the Dinosaurs? How Mass Extinctions Are Linked With Universe's Mystery Ingredient

asteroid impact
An artist’s impression of an asteroid impacting Earth. NASA/Don Davis

Dark matter is an exotic form of matter that can only be detected by its gravitational pull on other objects—other than this, it is invisible. Most scientists believe that dark matter is made up of tiny, hard-to-detect particles called weakly interacting massive particles (or WIMPs).

Amazingly, astronomers find that dark matter is five times more abundant than normal matter in the Universe. And now, new studies are suggesting that dark matter has actually affected the evolution of life on Earth.

In 1980, the science world was stunned when a team of researchers at Berkeley proposed that a massive meteor strike had wiped the dinosaurs and other fauna from the Earth 66 million years ago. Later, a giant impact crater of the same age was discovered buried under the Yucatan Peninsula. These discoveries forced scientists to consider that Earth was not isolated from its wider cosmic environment.

Tyrannosaurus Rex exhibit at the Natural History Museum of Leiden, Netherlands. Dean Mouhtaropoulos/Getty Images

The demise of the dinosaurs—along with about 75 percent of the species alive at the time—is not the only mass extinction in the geologic record, and not even the most severe. The great Permian extinction, 252 million years ago, destroyed up to 96 percent of existing species on land and in the sea.

These numbers point to global environmental catastrophes as the cause of the mass extinctions, and only two geologic forces are thought to be capable of producing such global upheavals—the impact of large asteroids and comets, and episodic eruptions of massive floods of lava.

Comet and asteroid impacts have severe immediate climatic effects through global dust and aerosol clouds. Flood lava eruptions produce aerosol clouds that cause short-term climate cooling, and they release huge amounts of greenhouse gasses, creating longer term and more severe global warming.

Over the last three decades, some scientists have found a good correlation of mass extinctions with impacts and massive volcanism. Curiously they have also turned up evidence that these events occur in a cycle of about 26 to 30 million years. This attracted the interest of astrophysicists, and several astronomical theories were proposed in which cosmic cycles affected Earth and life on the planet.

My own hypothesis linked the Earthly events to the motion of the solar system as it moves through the galaxy. Now, it seems that these geologic cycles may be a result of the interactions of our planet with mysterious dark matter.

How does dark matter affect our planet? Most dark matter can be found as huge haloes surrounding the disc-shaped spiral galaxies, like our own Milky Way. But in 2015 physicist Lisa Randall at Harvard, proposed that significant dark matter is concentrated along the central mid-plane of the galactic disk.

milky way
The Milky Way galaxy. ESA/Hubble & NASA

During the cyclic movement of the sun and planets through the galaxy, we pass through the mid-plane about once every 30 million years. At these times, the dark matter concentrated there tugs on the myriad Oort cloud comets found at the edge of the solar system. This gravitational perturbation causes some of the loosely bound comets to fall into the zone of the inner planets, where some would collide with Earth, producing a roughly 30 million year cycle of impacts and associated mass extinctions. As a result, dark matter may have killed the dinosaurs.

An even more dramatic event involves Earth passing through large dense clumps of dark matter as it moves through the galactic plane region. Several astrophysicists, including Nobel laureate Frank Wilczek, proposed that some of the dark matter can actually be captured by Earth. Moreover, the build-up of dark matter particles in Earth's core leads to their eventual mutual annihilation. This releases large amounts of energy—up to a thousand times the normal amount of heat in Earth's interior—periodically heating the inner Earth, and creating upward moving currents of hot, pliable rock.

earth from space
Earth from space. Scientists have suggested a new theory for how life on Earth could have started. NASA

The result may be pulses of geologic activity—volcanism, plate tectonic movements, sea-level variations and climate changes--spaced about 30 million years apart. So, this new hypothesis links major events in Earth's history, from external comet and asteroid impacts to internal processes that create large volcanic outpourings, with our movements through the galaxy, and with interactions with invisible dark matter.

Does this affect the probability of our experiencing a catastrophe in the near future? We may be in a dangerous part of the galaxy today, but it is still difficult to predict individual comet or asteroid impacts and volcanic eruptions.

However, it does mean that catastrophes are more important than previously thought—and that conditions on Earth are linked to happenings outside the planet.

Dr. Michael R. Rampino is a Professor at the Departments of Biology and Environmental Studies, New York University. He is author of Cataclysms: A New Geology for the 21st Century.

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