Posted on Mar 31, 2011 04:45:17 PM | William Cooke | 1 Comments
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What are the signs of spring? They are as familiar as a blooming daffodil, a songbird at dawn, a surprising shaft of warmth from the afternoon sun. And, oh yes, don't forget the meteors.
"Spring is fireball season," says Bill Cooke of NASA's Meteoroid Environment Center. "For reasons we don't fully understand, the rate of bright meteors climbs during the weeks around the vernal equinox."
In other seasons, a person willing to watch the sky from dusk to dawn could expect to see around 10 random or "sporadic" fireballs. A fireball is a meteor brighter than the planet Venus. Earth is bombarded by them as our planet plows through the jetsam and flotsam of space--i.e., fragments of broken asteroids and decaying comets that litter the inner solar system.
In spring, fireballs are more abundant. Their nightly rate mysteriously climbs 10% to 30%.
"We've known about this phenomenon for more than 30 years," says Cooke. "It's not only fireballs that are affected. Meteorite falls--space rocks that actually hit the ground--are more common in spring as well1."
Researchers who study Earth's meteoroid environment have never come up with a satisfactory explanation for the extra fireballs. In fact, the more they think about it, the stranger it gets...
Why more activity during the equinoxes?
Maybe because during the equinox the earths rotation is most in line with it's plane of orbit around the sun.