A new scientific study has found that the Earth is in greater danger than previously thought of a catastrophic meteor impact due to comet showers as the Sun and its planetary system pass through the dense mid-plane of the Milky Way's galactic disc.
According to researchers, analysis of new data suggests that there is a 26 to 30 million-year cycle of movement of our solar system in the spiral arms of our Milky Way galaxy that brings it into an "unsafe zone" of the galactic disc where the Earth is exposed to a higher risk of catastrophic meteor impacts. And according to researchers, evidence suggests that we are presently in the "unsafe zone" of the galactic disc.
Analysis of more accurate newly available data covering 260 million years by Professor Michael Rampino at the New York University and Professor Ken Caldeira at the Carnegie Institution for Science reveals a 26 to 30 million-year cycle of impact events that coincide with the passage of our Sun and its planets through a dense mid-plane zone of our galaxy.
When our Sun passes through this zone, gravitational tidal forces acting on the Oort Cloud -- a spherical cloud composed mostly of icy planetesimals located in the outermost reaches of the solar system -- pull dangerous comet showers into the inner region of our solar system consisting of small rocky planets, including our Earth.
"A cycle in the range of 26–30 Myr has been reported in mass extinctions, and terrestrial impact cratering may exhibit a similar cycle of 31 ± 5 Myr. These cycles have been attributed to the Sun's vertical oscillations through the Galactic disc, estimated to take from ∼30 to 42 Myr between Galactic plane crossings. Near the Galactic mid-plane, the Solar system's Oort Cloud comets could be perturbed by Galactic tidal forces, and possibly a thin dark matter (DM) disc, which might produce periodic comet showers and extinctions on the Earth."
According to the researchers, the episodes of dangerous comet showers generate meteor impacts linked with mass extinctions on our planet.
In the study published in the journal Monthly Notices of the Royal Astronomical Society, the scientists were able to identify six mass extinction events linked with periods of intense terrestrial impact cratering.
They identified an impact that was due to a large comet that hit the Earth off the Yucatan coast of Mexico about 65 million years ago. The impact is believed to have triggered the mass extinction of the dinosaurs.
"The correlation between the formation of these impacts and extinction events over the past 260 million years is striking and suggests a cause-and-effect relationship. This cosmic cycle of death and destruction has without a doubt affected the history of life on our planet," the researchers said.
"The correlation between the formation of these impacts and extinction events over the past 260 million years is striking and suggests a cause-and-effect relationship."
The last of these showers, according to researchers, occurred about 11 million years ago and coincided with the time of the Middle Miocene extinction of terrestrial and aquatic life forms that occurred about 14.5 million to 14.8 million years ago.
Rampino explained that astronomers may have assumed mistakenly that we are currently in a safe era of the 26-million-year cycle of mass extinctions caused by heightened comet showers, and that we are millions of years away from the next period of heightened risk of catastrophic meteor impacts due to periodic intensification of comet activity in the inner solar system.
"There is evidence that the comet activity has been high for the last one to two million years and some comet orbits are perturbed," Rampino said, "so we may be in a shower at the present time. That would agree with our position near the galactic mid-plane, where perturbations from dark matter etc. would be expected."
The study noted that the gravitational tidal forces that fling comets into our solar system and on a collision course with planets in the inner solar system are due partly to the clustering of dark matter around the dense disc of the galactic mid-plane.
Dark matter is an invisible form of matter found in dense clumps around galaxies, believed to account for most of the matter in the universe. Because dark matter does not reflect light, it cannot be detected with telescopes, but its presence is inferred from observed gravitational effects on visible matter and the large-scale structure of the universe.
[Image via Sir David Gill, 1843-1914, South African Astronomical Observatory/Wikimedia)