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article imageGeological catastrophes pinned to Galactic disc dark matter

By Karen Hardison     Apr 22, 2015 in Science
A recent study suggests that cycles of mass extinction, magnetic direction reversals, and crater impacts on Earth may be significantly influenced by rhythms of Earth's interaction with dark matter in the Galactic plane.
In cycles ranging from 30 to 40 million years (Myr), comet crater impacts, mass biological extinctions, geomagnetic directional reversals, rising sea levels, volcanic eruptions and other geological events occur. In a recent paper, Michael Rampino, a biologist at New York University, correlates the cyclical periodicity of such catastrophic geological and biological events with the passage of our Solar system through the plane of the Galactic disc, which occurs in a cycle of approximately every 30 Myr. If there are catastrophic events on Earth approximately every 30 Myr and if the Solar system passes through the Galactic plane approximately every 30 Myr, then what is it that drives the correlation between the cycles: the passage cycle and the event cycles?
"We are fortunate enough to live on a planet that is ideal for the development of complex life," Biology Professor Michael Rampino, lead researcher and author of the Oxford Journal published study, said to Daily Galaxy "but the history of the Earth is punctuated by large scale extinction events, some of which we struggle to explain."
The Solar System is described as having "vertical oscillations through the Galactic disc." The Galactic disc might be envisioned as spreading east to west, while the Solar system might be envisioned as traveling southerly to northerly but in a wobbly, sort of wavy path on its 250 Myr route around the Galactic center. On this wobbly path, our Solar system passes through the Galactic plane every 30 Myr, about eight times per 250 Myr orbital rotation. When envisioning these configurations, it becomes more clear why the Solar system will cross through the Galactic plane on a vertical cyclical passage.
The solar system takes 1 cosmic year lasting about 225-250 million years to orbit the Milky Way s ga...
The solar system takes 1 cosmic year lasting about 225-250 million years to orbit the Milky Way's galactic centre but during that time it oscillates above and below the galactic plane every 32 million years or so.
Physics 7, 41 (2014) | DOI: 10.1103/Physics.7.41
When the Solar system is positioned near the Galactic mid-plane, Rampino posits that perturbation (or disturbance) of the Solar system is exerted from two sources. The thin disc of dark matter (DM) — the Galactic center is stars, gas, dust and dark matter — causes perturbation as do gravitational tidal forces. These tidal forces come from galactic globular clusters of stars, which orbit the Galactic center. Of greater interest, and the object of Rampino's dark matter model, is the perturbation caused by dark matter to Earth's core and to other objects in the Solar system, especially to the Oort Cloud of comets.
The study accepts the theory that dark matter is composed of Weakly Interacting Massive Particles (WIMPs). Since DM WIMPs do interact with regular matter, dark matter can interact with particles in Earth's core. WIMPs are but one of several theoretical possibilities for the particle composition of dark matter, and CERN is fired up for 2015 to hunt for the DM particle.
The capture of interacting DM WIMPs in Earth's core, where they would lose velocity, would lead to a rise in number density since energy loss would prevent DM particles from escaping the core. DM density would be high enough for "mutual annihilation" of particles, releasing "large amounts of energy." This energy would generate heat and amplify the temperature of the core's geodynamo and, with intensified core temperatures, precipitate geologic events, such as the reversal of geomagnetic alignment, rising sea levels, increased volcanic activity, and tectonic plate rifts, all of which occur in event cycles of approximately every 30 Myr.
Dark matter perturbance of Oort Cloud comets could precipitate erratic changes to comet pathways resulting in collisions with Earth such as those evidenced by impact craters in cycles occurring approximately every 30 Myr. Both crater impact events and core-heat precipitated geological events have been linked to past mass extinctions, such as the three major ones of 66 Myr ago, 252 Myr ago, and 444 Myr ago. [Note that Rampino's approximations of Myr for cycles are far more precise and that the study of cyclical comet impact and geological events is still quite controversial.] Rampino explains the importance of interaction between Galactic dark matter and Earth:
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.
Rampino's study encourages examination of geological and biological events — previously determined to be exclusively terrestrial events — as being precipitated by extraterrestrial forces, those forces being dark matter perturbation, dark matter capture in Earth's core, and Galactic disc gravitational tidal forces.
If Rampino's model of Galactic disc dark matter interaction with our Solar system and Earth is correct, then deeper understandings are at hand for dark matter interaction and distribution; for Galaxy-wide geological events, such as planet satellite and exoplanet crater impacts; and for Earth's geological catastrophes and mass extinctions.
The recent paper by Michael R. Rampino, Department of Biology, New York University, "Disc dark matter in the Galaxy and potential cycles of extraterrestrial impacts, mass extinctions and geological events," was published in Monthly Notices of the Royal Astronomical Society, published online February 18, 2015.
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