The Solar System’s movement through a dark-matter halo enveloping our Milky Way Galaxy may perturb the orbits of comets and lead to additional heating in the Earth’s core, both of which could be connected with catastrophic geological and mass extinction events, says Prof Michael Rampino of New York University, who is the author of the study published in the Monthly Notices of the Royal Astronomical Society.
This artist’s impression shows the structure of our Milky Way Galaxy, including the location of the spiral arms and other components such as the bulge. Image credit: NASA / JPL-Caltech / ESO / R. Hurt.
Previous studies have shown that our planet rotates around the center of the Milky Way Galaxy once every 250 million years.
But the Earth’s path is wavy, with the Sun and planets weaving through the crowded Galactic disc approximately every 30 million years.
Analyzing the pattern of the Earth’s passes through the disc, Prof Rampino noted that these passages seem to correlate with times of comet impacts and mass extinctions of life.
The famous comet strike 66 million ago that led to the extinction of the dinosaurs is just one example.
What causes this correlation between Earth’s passes through the Galactic disc, and the impacts and extinctions that seem to follow?
“While traveling through the disc, the dark matter concentrated there disturbs the pathways of comets typically orbiting far from the Earth in the outer Solar System,” Prof Rampino said.
“This means that comets that would normally travel at great distances from the Earth instead take unusual paths, causing some of them to collide with the planet.”
But even more remarkably, with each dip through the disc, the dark matter can apparently accumulate within the Earth’s core.
Eventually, the dark matter particles annihilate each other, producing considerable heat. The heat created by the annihilation of dark matter in Earth’s core could trigger events such as volcanic eruptions, mountain building, magnetic field reversals, and changes in sea level, which also show peaks every 30 million years.
Prof Rampino therefore suggests that astrophysical phenomena derived from the Earth’s winding path through the Galactic disc, and the consequent accumulation of dark matter in the planet’s interior, can result in dramatic changes in Earth’s geological and biological activity.
His model of dark matter interactions with the Earth as it cycles through the Galaxy could have a broad impact on our understanding of the geological and biological development of Earth, as well as other planets within the Galaxy.
“We are fortunate enough to live on a planet that is ideal for the development of complex life,” Prof Rampino said.
“But the history of the Earth is punctuated by large scale extinction events, some of which we struggle to explain. It may be that dark matter – the nature of which is still unclear but which makes up around a quarter of the Universe – holds the answer. As well as being important on the largest scales, dark matter may have a direct influence on life on Earth.”
“In the future, geologists might incorporate these astrophysical findings in order to better understand events that are now thought to result purely from causes inherent to the Earth,” he said.
“This model provides new knowledge of the possible distribution and behavior of dark matter within the Galaxy.”
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Michael R. Rampino. 2015. Disc dark matter in the Galaxy and potential cycles of extraterrestrial impacts, mass extinctions and geological events. MNRAS 448 (2): 1816-1820; doi: 10.1093/mnras/stu2708
