Dec 23, 2010 09:06 GMT  ·  By
Rendition of cosmic rays hitting particles in Earth's atmosphere and breaking apart in particle showers as a result
   Rendition of cosmic rays hitting particles in Earth's atmosphere and breaking apart in particle showers as a result

A new study proposes an interesting explanation for the regular variations that the biodiversity on our planet exhibits almost like clockwork. Experts now believe that the wobbling path our solar system takes as it's traveling through the Milky Way may have something to do with this.

One such extinction event takes place every 60 million years or so, at precisely the same time when the solar system moves north of the galactic disk's average plane. Many scientists have proposed in the past that a causal link exists between the two.

Whenever this happens, biodiversity here on Earth experiences a noticeable dip. One of the mechanisms proposed to explain this makes use of high-energy subatomic particles, which may hit our planet in much larger numbers when we leave the plane of the galactic disk.

Cosmic rays are known to permeate the intergalactic space, and so it could be that our solar system is more subjected to their influence than on other occasions.

Also worthy of note here is the fact that the solar system features a protective layer, called a heliosphere, which is generated by the Sun. Usually, it is able to keep harmful radiation at bay.

Still, when the amount of cosmic rays exceed certain levels, they might be able to pierce through the solar system's defenses, causing havoc on all the planets, and especially Earth.

According to measurements in the new investigation, it could be that the northwards wobble in our solar system's path exposed the planet repeatedly to radiation levels that shot up by a factor of 24.

This is the first time numbers are introduced in this theory. “Even with the lowest assumption, this exposure provides a real stress on the biosphere periodically,” explains researcher Dimitra Atri.

The expert, who is the lead author of the research, is based at the University of Kansas. She presented her team's findings last week in San Francisco, at the 2010 annual fall meeting of the American Geophysical Union (AGU).

What's interesting to note about cosmic rays is that they do not cause harm directly. When they slam into the atmosphere, they hit various particles contained within, and then break apart in other, lower-energy elementary particles, such as for example muons.

“It's kind of a particle shower,” Atri explains, saying that, even now, vast amounts of cosmic rays are hitting every square inch of the planetary surface several times each second.

The thing that makes muons dangerous is their ability to ionize (electrically charge) molecules, by stripping away spare electrons. This can cause massive damage to the DNA of all living things.

However, everything that evolved here on Earth is already accustomed to handling this background damage. “Life has evolved with this kind of radiation dose,” the expert tells Space.

But life is not accustomed to experiencing spikes in these radiation levels, which is why extinction levels occur whenever spikes are recorded.