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Astrobiology model predicts deep impact periods with extinctions

Published by under Cosmos,News categories on July 19, 2008

Large impact crater of merteoriteScientists from the Cardiff Center for Astrobiology have developed a model showing that our solar system goes through the plane of the galaxy every 35-40 million years. This is accompanied by comets hurtling into the inner solar system, coinciding with mass life extinctions on Earth. The researchers estimate that we are now in one of the predicted collisions’ period.

The researchers have produced a mathematical model demonstrating that our Sun ‘bounces’ up and down through the plane of the Milky Way Galaxy. According to the model, as we pass through the densest parts of the galaxy’s plane, gravitational forces tear comets from their paths, and send them plunging into the depths of our solar system. Inevitably, some of them collide with Earth.The idea presented in the collision model is not new in the scientific community. In 1998, researchers concluded that at least two mass extinctions of life forms on Earth had taken place at a time when the Sun was passing through the spiral arms of the galaxy.

The Cardiff team, composed of Dr. Janaki Wickramasinghe and Professor Bill Napier, has uncovered further evidence to support this theory. According to their calculations, the Sun goes through the plane of the galaxy every 35-40 million years. The researchers evaluated the age of craters on the face of the Earth, and discovered that every 36 million years or so, the collision frequency of comets with the Earth increases by an order of magnitude.

There is no doubt that a collision with comets can threaten life as we know it. According to astronomers, our previous encounter with one of the spiral arms of the galaxy (Sagittarius-Carina), 65 million years ago, resulted in the extinction of almost all the dinosaurs, along with 57% of all kinds of terran vegetation.

On the bright side, the scientists claim it is possible that the collision periods enable microbial forms of life to leave the Earth, carried on the dust sprays and stony shards that break off the Earth at the moment of impact. Those miniscule ‘shuttles’ may eventually leave the solar system entirely, spreading the ‘seeds of life’ throughout the nebulae and the gas and dust clouds that are scattered throughout the galaxy. In fact, according to the Panspermia Theory, the early forms of life reached Earth in this manner, carried safely in the core of a passing comet.

The Cardiff scientists believe that more money and efforts should be invested in searching for near-Earth objects (NEO), and into developing possible strategies for dealing with such a high velocity encounter.

“There are two areas where I think we are deficient,” says Professor Bill Napier, one of the paper’s authors and an Honorary Professor at Cardiff University. “First, the inner solar system is almost unexplored in the sub-kilometer range, which is where I think a lot of cometary fragments exist. Second, we should be looking for extremely dark bodies – dormant comets – which may not be getting picked up in current search programs. They should be bright in the satellite infrared.”

The researchers deduce from both the impact crater records and the Sun’s position near the Galactic plane that we are currently in a potential bombardment period. Luckily for human kind, the collisions’ period has a half-life of about two million years, meaning that the collisions are spread over a long time. This also means that the risk for the next mass extinction might be nearer we suspect, and we must prepare the necessary media to drive this contigency.


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