A cosmic drama unfolded in southern Ontario on the night of Friday, November 18, prompting an international collaboration and meteorite hunt. Just before midnight EST, the Catalina Sky Survey in Arizona spotted a small object heading toward Earth.
This small asteroid, now designated 2022 WJ1, was tracked by many observatories around the world for the next three hours before it impacted southern Ontario at 3:26 am EST on November 19.
The few hours of warning about the asteroid impact allowed several members of the Western Meteor Physics Group and the Institute for Earth and Space Exploration (Western Space) to move outside and find a clear time to observe the incoming object.
David Clark, a PhD student in geophysics, drove to the predicted fall area early in the morning and managed to see the fireball with his own eyes parked near Niagara-on-the-Lake at the intersection of Highway 403 and Niagara Regional Highway 55 (formerly Highway 55).
“It passed right over at the scheduled time and was clearly green in color,” Clark said. “Several minutes later a noticeable sonic boom was heard.”
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Professor of physics and astronomy Paul Wiegert was also alerted early enough to see the fireball.
“I watched from Brescia Hill on the western campus. Although cold and windy, the hill had a clear view to the east, where I expected to see only a distant flash. Then suddenly the fireball appeared, passing almost about. Wow! It was easily visible through broken clouds and noticeably orange-red in color,” Wiegert said.
Map of the fireball’s ground track to its endpoint (marked with a black ‘x’). The other dots indicate the locations of the All-Sky camera network that observed the fireball.
The bright fireball produced by the terminal fall of 2022 WJ1 was also observed by Western’s All-Sky Camera Network in southern Ontario at 03:26 AM on November 19, as predicted. The meteoroid entered the Earth’s atmosphere just south of Woodstock, moving eastward as a bright fireball to its end about 20 km above Grimsby, Ontario.
Analysis of the video data, also captured by cameras provided by Curtin University (Australia) within the Western Network, suggests that the meteor fragments are likely to have landed near the southern shore of Lake Ontario mainly east of Grimsby. .
“This fireball is particularly significant as the parent meteoroid was observed telescopically before it hit the atmosphere. This makes it a rare opportunity to link telescopic data from an asteroid to its breakup behavior in the atmosphere to gain insight into their internal structure,” said Peter Brown, Canada Research Chair in Small Planetary Bodies at Western.
Only six other asteroids in history have had prior warning of their impact, and all cases have been detected a few hours before their entry into the atmosphere. This is the first predicted event to occur in a highly populated area and within the range of instruments dedicated to measuring fireballs.
Despite widespread cloud cover over southern Ontario during this period, six cameras in the All-Sky Camera Network detected the fireball along with the Western Canadian Meteor Orbit Radar, providing an unprecedented record of the disintegration of this small asteroid in the atmosphere.
“This remarkable event will provide clues about composition and strength that, when combined with telescopic measurements, will allow us to understand how small asteroids break up in the atmosphere, important knowledge for planetary defense,” Brown said.
The final piece of this cosmic puzzle is the recovery of meteorites associated with the 2022 WJ1 fireball, and researchers are asking for public help. Residents in the area between Port Weller and Virgil, in particular, should be on the lookout.
“We know from camera records and weather radar that tracked the falling debris from the fireball that the meteorites almost certainly hit the ground near or east of Grimsby. What we need now to complete this story is to recover some of these rocks and find out what kind of material formed asteroid 2022 WJ1,” Brown said. “This is very much like a sample return space mission, but in this case the sample fell on us.”
Meteorites can be recognized by their dark, often scalloped exterior, a molten crust that is only a millimeter deep, covering a gray stony interior. They will generally be denser than “normal” rock and will often be attracted to a magnet due to their metal content. Meteorites are not dangerous, but if they are recovered, it is best to put them in a clean plastic bag or wrap them in aluminum foil. They should also be handled as little as possible to help preserve their scientific value. In Canada, meteorites belong to the owner of the land on which they are found. If people plan to search, they should always get permission from the landowner before venturing onto private land.
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