SPRINGTIME FIREBALL MYSTERY: The inner solar system is littered with dusty, gravelly debris from decaying comets and shattered asteroids. Every night Earth scoops up tons--literally tons--of this material, resulting in a slow drizzle of bright fireballs. Astronomers call them "sporadics." If you stay outside all night long, you might see as many as a dozen if the weather is clear. On April 8th, a spectacular example split the sky over Veszprem, Hungary:
Photographer Monika Landy-Gyebnar reports: "I was out photographing the sunset, then waited until the International Space Station (ISS) and somewhat later the Progress MS-07 flew overhead. The fireball fell during the time between the two spacecraft. The flower in the foreground is a local pasque flower (Pulsatilla nigricans) which I wanted to include in my picture of the ISS."
Landy-Gyebnar says the magnitude of the fireball was about -10--in other words, more than 100 times brighter than the planet Venus.
Now for the mystery: Sporadic fireballs appear 10% to 30% more often during northern spring compared to other times of year--and no one knows why. "We've been aware of this phenomenon for more than 30 years," says Bill Cooke of NASA's Meteoroid Environment Office. "It's not only fireballs that are affected. Meteorite falls--space rocks that actually hit the ground--are more common in spring as well." Perhaps there is a diffuse swarm of meteoroids scattered in the April-May arc of Earth's orbit, giving rise to the extra fireballs. If so, its origin is unknown. Source