Dinosaur Demise and Earth's Movement in the Milky Way

Author:  Jessica Kloss

Institution:  Princeton University
Date:  May 2008

A recent study at the Cardiff Centre for Astrobiology suggests that mass life extinctions on Earth correspond to the solar system's movement in the galaxy. Center director Professor Chandra Wickramasinghe and the Cardiff team developed a computer simulation that mapped the movement of the solar system in our galaxy, the Milky Way, and found that times of greater comet bombardment , and therefore mass extinctions , are linked to our movement through the galaxy.

The Sun and the stars that make up the Milky Way rotate around the galactic center, forming a disk called the galactic plane. But the Cardiff team found that the Sun's movement is not perfectly aligned with this disk. Instead, the plane of the Sun's orbit is slightly tilted compared to the galactic plane, so that approximately every 35 to 40 million years, we "bounce" up and down through the densest region of the galactic plane. During this time, the chance of comet collision increases tenfold.

Unfortunately for species on Earth, as the solar system passes through the densest part of the galactic plane, new comets plunge into the solar system , some of them colliding with the Earth. Evidence from the craters on the Earth confirms that about every 36 million years, there is a period when the Earth suffers a greater number of collisions. "It's a beautiful match between what we see on the ground and what is expected from the galactic record," said Professor William Napier of the Cardiff Centre for Astrology, who co-wrote a paper on the subject to be published in the Monthly Notices of the Royal Astronomical Society.

The current position of the solar system in the Milky Way suggests that another period of greater comet bombardment is not far away. But while such bombardments are believed to have been the end of the dinosaurs, and are generally treated by species on Earth as bad news, it may also help spread life to other parts of the universe. When comets slam into the Earth, debris containing micro-organisms is thrown into space , and could have a chance to spread in the universe.

Written by Jessica Kloss

Reviewed by Jeffrey Kost

Published by Pooja Ghatalia.