Meteors in the News – DoD Classifies Fireball Data and Boy Gets Hit By Meteorite
June 13, 2009 4 Comments
Two news stories related to meteors hit the news wires the past few days.
On Thursday came a story about the United States Department of Defense (DoD) classifying data on fireballs. Specifically data taken by their Defense Support Program satellites that monitor the world for signs of missile launches. As it turns out, these satellites were also very good at detecting bright fireballs as they “burn up” in the Earth’s atmosphere. For the past 15 years, the DoD has been sharing fireball data with the scientific community. For some examples, a collection of releases for past fireballs can be found here.
More than 15 years ago, the DoD’s fireball data was classified. This now appears to be the case once again. I have yet to see an official reason for this, though usually the real movie behind classifying information has less to do with the object itself but rather, what the data can tell others about the detection capability of our satellites. Perhaps it has something to do with our soon-to-be upgrade to a newer, more sensitive constellation of satellites. The Space-Based Infrared System (SBIRS) is the DoD’s next generation system and it is possible that the DoD would like to keep its capabilities hush for awhile.
Regardless, the loss of this data to science isn’t too bad. We will still be able to detect and study fireballs over a good fraction of the world. This is becoming more and more possible due to the proliferation of low light camera systems operated by astronomers and for security purposes.
Yesterday’s story comes out of Essen, Germany. There is a report that a 14 year old boy was struck by a meteorite on the hand. As reported by The Telegraph, the boy stated that “At first I just saw a large ball of light, and then I suddenly felt a pain in my hand. Then a split second after that there was an enormous bang like a crash of thunder. The noise that came after the flash of light was so loud that my ears were ringing for hours afterwards. When it hit me it knocked me flying and then was still going fast enough to bury itself into the road.”
Getting hit by a meteorite is an extremely rare event. There is only one documented case, that being of a woman from Alabama being struck back in 1954. So being hit is not impossible. Still the story out of Germany has some inconsistencies.
The meteorite is said to be very small, only the size of a pea. No problem there. It is also reported that it struck the boy on the hand. Again unlikely but no problem. Everything else about the story is problematic.
First let’s run down what a meteorite fall would look like. Many people have seen Hollywood’s version of a meteorite fall. Great examples include the CGI meteors in many of Michael Bay’s movies (Transformers, Armageddon). The meteors are portrayed as relatively small but crashing to the ground at a low angle at 1000’s of miles per hour. They are usually flaming with smoke trails behind them. The meteorites then crash through buildings, bridges, whatever. This is true for large objects.
For your “run-of-the-mill” meteorite-dropping fireball (fragments up to the size of a volleyball), the event will look very different. The original small asteroid will hit the atmosphere at velocities of ~10-70 km/s. Its passage through the atmosphere is violent as air is compressed in front of it in a bow shock. Eventually there comes a point when the pressure is too great and the meteoroid starts to fragment. On many occasions there is a final disruption event. It is usually at this point when the meteoroid has broken into much smaller pieces that a bright flash, or terminal flash, is seen and sonic booms are heard. The sonic boom are caused by the small meteoroid pieces decelerating rapidly below supersonic speeds due to atmospheric drag. So great we have a loud noise and a bright flash just like those mentioned in the German article. Problem is, all of this happens tens of miles up.
So here’s some problems with the “meteorite hits boy” account:
- “30,000 mph space meteoroid“: Well, yes and no. The meteorite might have been traveling 30,000 mph when it first hit the atmosphere but it was moving much, much slower by the time it hit the ground. After disrupting into smaller pieces, the pea-sized meteorite would have been in free fall from a height of many tens of miles or kilometers. Air drag would slow it to its terminal velocity which for a pea-sized rock is rather slow, slower than the speed limit on most highways.
- “saw a large ball of light“: The fireball produced by the meteoroid traveling through the atmosphere would have been bright enough to see even during the day. But, it would have been seen over many 100’s of miles, and I know of no other sightings. Also the fireball would have ended when the meteoroid disrupted. That means the fireball would have ended many tens of miles up and many minutes before the pea-sized piece hit the ground. A rock of that size would have taken a few minutes to fall from 20-40 miles up. When it did hit the ground it would have looked no different then if a small rock had been thrown off of the top of a building.
- “enormous bang like a crash of thunder“: Again any sonic boom caused by the fireball would have occurred many minutes before the meteorite hit the ground. Also those sonic booms would have been heard over many tens of miles.
- “When it hit me it knocked me flying and then was still going fast enough to bury itself into the road“: Not likely since it was traveling so slow. There is a German article that shows the size of the meteorite and its resulting “crater”. You can see it here. Again, a meteorite this small would have hit the ground too slowly to do any damage to the ground. The meteorite would have simply bounced along the ground.
So what does this story tell us? Either it’s a complete hoax and there never was a meteorite fall. Yes, it’s true that researchers in Germany have confirmed that the rock is a meteorite but that doesn’t mean much yet. Anyone purchase a small legit meteorite of this size off of Ebay for a few dollars. It is also possible that this is a real meteorite fall and the boy’s “story” is fabricated. Maybe to live up to many people’s incorrect idea of what a meteorite fall would look like.