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Harbor video may help track meteor path over Petersburg


Petersburg Harbor video surveillance footage may confirm a meteor did pass over Petersburg in the early morning hours of Sat., Nov. 21. Eyewitness reports placed the fireball at times ranging between 2:22 a.m. to 2:33 a.m. Petersburg Harbor video surveillance footage shows a bright flash of light lasting for two seconds on nearly all its camera feeds at 2:25 a.m.

The Petersburg Public Library video camera also captured images of a bright flash of light at exactly the same time.

Johnson Space Center NASA scientist Marc Fries points to data that suggests a falling meteor shook Mitkof Island, which could mean many Petersburg residents woke up to the flash of a fireball and the blast of a sonic boom.

The Petersburg Pilot sent the harbor video footage to Fries. He will analyze the images to see if he can more accurately pinpoint the direction of the meteor, the location of any surviving meteorites and if it corresponds to the radar data.

Johnson Space Center’s Curator of Planetary Ices and Organics Marc Fries keeps an eye out for meteor reports and five Petersburg residents, reported sightings on the American Meteor Society webpage.

“We (NASA curators) handle extra terrestrial materials,” Fries said. “One of the things I study is locating meteorite falls with weather radars. People reported large sonic booms. A meteor has to get really far down into the atmosphere to produce sonic booms, which means there’s a high likelihood they reached the ground.”

On Saturday, Nov. 28, Fries emailed the Pilot that he is still trying to track the path of the meteor and is anxious to receive more eyewitness reports from people that saw the light or felt the tremors from a sonic boom that shook residents awake on Nov. 21.

A sonic boom occurs when an object travels faster than the speed of sound, a speed roughly in excess of 700 mph. Sound waves are similar to water waves and a sonic boom is like a wake.

“A sonic boom can be powerful enough to shake the ground or the house,” Fries said. “In order to hear a sonic boom you have to have a large meteorite to get through the atmosphere.”

Meteorites reach the ground within about 90 seconds to around eight minutes after the fireball, blasting a turbulent wake of sound as they fall. Fries analyzed NOAA weather radar data from a station near Sitka and found what might be reflected radar energy from those sound waves at around 2:33 a.m. According to the video footage, the radar reflections near Duncan Canal occur eight minutes after the fireball.

Fries said sonic booms are typically heard within roughly 10 kilometers from where they were created, meaning that if it was a meteor, it went directly overhead Petersburg.

“It comes with no guarantees but that’s the best I can find,” Fries said.

One thing radar doesn’t detect is lightning, which did strike in the area Saturday morning as well, according to Tom Ainsworth, head of NOAA’s National Weather Service in Juneau.

“Yes, there was lightning in the area,” Ainsworth said. “But not everyone there agrees it sounded like thunder. The Tsunami Warning Center said there was no sign of seismic activity in the area at that time. Not having been there myself, it is still not completely known what caused the noise.”

Fries and other colleagues are also looking into seismometer data and he said they have noticed possible readings caused by a sonic boom.

It’s possible some remnants of the falling debris could be found he woods next to Duncan Canal, or somewhere nearby. Fries said to look for glassy black objects ranging in size from a marble to a fist.

“It looks kind of like pottery glaze, the interior of the rock is a different color than the outside, which is fusion crust from when it burns through the atmosphere,” Fries said. “It acts like fried ice cream. These things are very cold in space. They only go through the atmosphere for a few seconds. It’s hot enough to melt rock but it happens so fast that it doesn’t heat up the whole rock.”

If a meteorite were a little larger than a fist, the size of a loaf of bread for example, it would be big enough to cause a crater or damage to structures. But that’s not very likely, according to Fries.

Since 1997, nineteen confirmed meteor events have been recorded in the U.S. and Canada using data from NOAA’s radar network, although it’s likely they occur every day somewhere around the world. Given that 70 percent of the earth is covered in water, most of them are lost, and many aren’t noticed if a meteor falls during the day. Different types of meteorites fall to the earth and produce different effects. The “fireball” effect that was described in Petersburg points to a meteor that consisted of an accumulation of small pieces.

“If it’s really crumbly to start with, an accumulation of small pieces called a bolide, you’ll see a very bright fire ball and bolides are more likely to drop meteorites,” Fries said. “When that hits the atmosphere it comes apart like a shotgun blast.”

Four meteorites have been found in Alaska.


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