-- a troublesome, extraterrestrial invader from afar.The event was a smaller version of the 1908 meteorite explosion above Tunguska, Siberia that unleashed an explosion force equal to 15 megatons of TNT. That blast flattened some 770 square miles (2,000 square kilometers) of forests.
Similar wake-up calls have peppered the Earth throughout the ages -- and our planet has the scars to prove it.
Rock of the ages
Between 30 to 50 times a year, scientists say, a fireball comes screaming through Earth's atmosphere, but chances are you never hear about most of these intruders.
Since the late 1970s, military satellites have spotted about 400 such events. So far most of the data have remained classified.
Scientists estimate that nine out of 10 fireballs remain out of public and scientific view. Of course, there is the supposed mega-blast that wiped out the dinosaurs 65 million years ago. But an event of that magnitude is exceedingly rare, one that is not real to most people.
"We have a capability in the satellites of seeing very bright, transientevents in the atmosphere. Anything that's big enough for us to see is somethingworth paying attention to."
"Conversely, I can show people evidence of real strikes inflicting local and regional damage less than a century ago," said Brigadier Gen. Pete Worden, deputy director for Command and Control Headquarters for the Air Force.
"Even more compelling are the frequent kiloton-level detonations our early warning satellites see in the Earth's atmosphere. These are threats the public and its leaders will take seriously," he said.
Worden emphasized he was speaking solely for himself. The Defense Department has no official view on threats from space rocks.
The watch for space rocks
But getting the word out on these heavenly visitors appears to be a cumbersome process.
"There doesn't seem to be a systematic and recognized approach for dealing with this kind of data," said Richard Spalding, an engineer at Sandia National Laboratories at Kirtland Air Force Base in Albuquerque, New Mexico.
"We have a capability in the satellites of seeing very bright, transient events in the atmosphere. Anything that's big enough for us to see is something worth paying attention to," he told SPACE.com.
Spalding is one of a growing cadre of experts familiar with hush-hush satellite data who argue that such information should be released faster and shared throughout the scientific community.
One idea is to build a "response capability" using Air Force Defense Support Program (DSP) satellites.
These globe-circling spacecraft could issue a "near-real-time" message of an airburst, spelling out the location and at what altitude the explosion may have occurred, said Richard Davies, president and chairman of the Western Disaster Center, Moffett Federal Air Field, California.
The center is a non-profit research group focused on high-tech ways to improve disaster and emergency management.
"There is [a] need to use existing capabilities to increase the level of monitoring," Davies said. "The capability is there to do this in real-time, not report on an event months later. Sometimes it has taken that long.
"We could have a small Tunguska-like event over a populated area with people hurt and killed," he said. "It might take hours or even days before there is any communication from them."
Davies said that such sky-watching duties using current and future military spacecraft could be folded into the newly created Global Disaster Information Network (GDIN).
Established by President Clinton on April 27, the GDIN is a multi-federal agency group whose duty is to use information technology to reduce loss of life and property from natural and human-made disasters.
The issue is stirring attention overseas as well.
Joining the call for more action on threatening space rocks is Spaceguard U.K., an international group of scientists and researchers based in Salisbury, England.
A British government task force is investigating the threat posed to Earth by incoming space objects. It is to make its recommendations to Britain's Minister of Science next month.
The process of releasing information about space rocks "certainly could be improved," said Edward Tagliaferri, a consultant to the Aerospace Corporation in El Segundo, California.
He analyzes infrared data gleaned from Defense Department satellites and, if given a go-ahead, releases that data to the scientific community. He would not say which government agency dictates the release of such data.
"Right now, it's done on a case-by-case basis," Tagliaferri said. It's not like they aren't aware of the value of this data. It's just that the workload is significant on their part," he said.
Things that go boom in the night
One event earlier this year points to the need for quick, accurate data regarding incoming meteorites.
On January 18, over a remote area of northwest Canada,
, releasing the equivalent blast of a 4- to 5-kiloton bomb."It was a big object. I estimate somewhere between 6 and 9 feet (2 and 3 meters) in diameter. We don't usually get hit that hard except once every five to 10 years," Tagliaferri said.
Defense Department satellite sensors caught the incoming object as it plunged toward Earth, he said.
Plowing through the atmosphere above Yukon Territory, sonic booms startled residents as far away as British Columbia and Alaska.
When the fireball exploded at an altitude of 16 miles (25 kilometers), it turned darkness on the ground to daylight.
So bright was the explosion that streetlights operating on solar cells turned themselves off.
As the meteorite extinguished itself, the lights immediately turned back on, overloading the local power grid. That in turn caused electrical switching hardware to fail.
Being left in the dark by a natural event is one thing. But to unsuspecting townspeople, might they not consider it a terrorist attack?
"Absolutely. These types of events really do mimic nuclear detonations. There are definite advantages to the timeliness of releasing this kind of information," Tagliaferri said.
Also, there are political powder kegs around the globe. A fireball event could cause a literal spark that lights a fuse.
"When you go down the list of Pakistan and India, China and Russia, North Korea and South Koreathere are enough people who are at odds with each other. One of them could be tempted to retaliate to an event they thought was initiated by somebody else. We need some mechanism where government to government can communicate in a credible manner about a natural event," he said.
"One of these things is going to hit somewhere and really cause some serious flap or damage, or both. It's just a matter of time," Tagliaferri said.
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