Last Sunday a huge fireball lit up Cranbrook’s whole western horizon. From high up, first a swiftly moving ball of yellow light caught the eye. It rapidly gained brightness, until it turned into a blue-white welding arc. A small orange globule broke off and followed it along its wake. Then it suddenly flared and a spray of brilliant white light flashed out and lit all the sky for miles around and casting shadows on the ground. A large blue-white fireball zipped out of that dazzling light, with one smaller orange fireball chasing after it, slowing down and dropping over the horizon into the smoke haze until it dimmed out of sight. Minutes later, a dull rumbling sound like thunder grumbled in the distance.
In disbelief a witness in Crawford Bay “almost ducked” as she saw it rocket close overhead, the eerie silent blue-white fireball and behind it two smaller reddish-orange balls falling away and arcing down not too far away to the North. There was a quiet pause as she looked North wondering—what was that? Then KRACK-WHAMMMM! recoiled to the tremendous crash of a sonic boom–so loud she felt it vibrate inside her chest, then a crackle and continuous waterfall of noise as the air tumbled back in to fill the tunnel of low pressure air the supersonic fireball had rammed through the sky. For an endless twenty seconds this shook the house, rattling the windows, the garage doors and even the ground before dying away. For a second she imagined it was a nuclear bomb blast. I’m not kidding, it was that loud! she said.
Was it a small nuke? NASA’s JPL website reported a monitoring satellite saw an air blast at 36km altitude equivalent to 0.13 kilotons of TNT.
Attachment KasloMeteor.gif above is a GIF slideshow with frames displayed every half second. When viewed in webmail or on a web browser, it will play the animation. Moon at lower left. Photo credit COTR meteor cam 4 Sep 2017.
But videos show it was a meteor, a rock from outer space, with pieces falling off as it went along.
So, where did it hit the ground? BC has a network of meteor cam stations watching to find where these hit. The College of the Rockies has a meteor cam, and it tracked it for about ten seconds, starting from 11:11:26pm. Six or more security cam videos saw it. One good video from Spokane (near Gonzaga University) was used with the College video, and a photo from just South of Crawford Bay near the marina, to triangulate where the meteor hit and was able to give us a good idea. Esko Lyytinen, a retired mathematician of the Finnish Fireball Network, kindly analyzed our video. Summarized as follows:
The main 50kg piece would have hit about 5km East of Kaslo around: (49.8731 N, 116.8457 W). “It flew directly over Crawford Bay but not as far as Meadow Creek”. The main piece was last seen at 49.7603 N, 116.8350 W, still 18.9km high. The 100g sized fragment from the brightest flash would have hit 2.5 km South and 1km East of Riondel at around (49.7381 N, -116.8393 W). The winds may have moved the main fragment about 750 m to the East and the 100 g fragments about 1.7 km to the East. Thus the NE area of Crawford Bay would probably be favorable for finding fragments. As well as from Gray Creek North to Crawford Bay along the road. But fragments can veer in direction: after talking to witnesses, Dr. Alan Hildebrand is worried the main piece may have gone into Kootenay Lake.
These fragmented meteors don’t make craters, craters are usually made by much larger solid nickel-iron ones. This meteor was likely slowed down to around 200 km/h by the time it reached “dark flight”. If the basket-ball sized 50kg chunk hit soft ground, it would have left a big dent about as deep as its diameter, then bounced up and landed on the surface again. Unless it hit solid bedrock and shattered. The smaller fragments (100g would be around golf ball sized) would have just bounced like normal rocks.
Meteorites that strike the ground are not smoking hot as depicted in Hollywood movies, so there is no need to worry about them starting a forest fire. They start off cold in outer space (about zero degrees C for meteoroids around Earth’s orbit). Their outer surface gets white hot as it compresses the air into a plasma sheath, but this blowtorch heat is slow to penetrate the rock. This hot layer fuses and evaporates and is blown off as droplets, dust and vapour before it can heat the inside. So the inside remains cool during the brief 10 second fiery fall through the atmosphere. It’s rare to find a hot or warm meteorite, some have even been found with frost on them. But the outside skin often has a one millimetre thick melted “fusion crust” with thumb-sized worn hollows.
Video Frame at 11:11:34.066 seconds showing fireball and pieces falling off along path (photo rotated). Photo Credit R. Nowell, COTR Meteor Cam.
Judging from factors like how high it fragmented, porosity, speed, cometary orbit from beyond Pluto, Esko is betting it’s a common, stony non-metallic meteorite, a “chondrite”. These are the most common types, they make up 86% of meteorites that are recovered. Formed of dust, clay and small sand grains surrounding “chondrules”: small beads of silicate minerals like olivine and pyroxene. (Olivine is a magnesium iron silicate common on Earth but quickly weathered). May contain small amounts of magnetite, nickel-iron, or even flakes of metal. Density about 3.5 g/cm^3 as heavy as basalt rock. Very old, from primitive asteroids originating from the early solar system 4.5 billion years ago
Chondrite Meteorite. Polished face showing chondrules and metal flakes. Dark shiny fusion crust. Photo Credit H. Raab, CC Wikipedia article. https://en.wikipedia.org/wiki/Chondrite
Since it had a cometary orbit of about 50AU, Esko supposes it may even be a carbonaceous chondrite with lighter density. That is a rare type of primitive meteorite with organic compounds such as water, amino acids and hydrocarbons.
WHAT TO LOOK FOR: Chondrites: Look for rocks that a magnet will stick to. The surface may have a thin grayish fusion crust (a thin melted layer one or two millimetres thick) and scattered thumb sized hollows (worn away by atmospheric friction called regmaglypts). Although rarer meteorites like the Tagish Lake carbonaceous chondrite meteorite looked like black charcoal briquettes.
Ignore layered sedimentary rocks (shale, limestone, dolomite) since these require an ocean to form, and this wouldn’t be found on an asteroid in outer space. Also, if it has holes or bubbles inside (like pumice) that was likely from lava flows (basalt-magma) cooled with trapped volcanic gases, on Earth (although there are rare exceptions: a large asteroid like Vesta had volcanoes). Also, ignore rocks containing quartz or calcite, since they form in high pressure, hot watery solutions.
Magnets: Since a lot of chondrite types contain iron oxides like magnetite, and some metal rich ones contain nickel-iron chondrules, a rare-earth magnet should stick to most.
Value: If a hiker finds a piece, it could be worth a lot of bucks per gram or it may be disappointing. Common iron meteors are only $.50/gram to $5/gram, rarer stony meteorites $2 to $20/gram, and really rare ones $100 or $1000/gram or more, depending if they have embedded gems or if they’re from Mars or the Moon. And some meteors are dense and heavy, so they go a long way. For example, back in 2000, the rare carbonaceous chondrite meteor that landed on frozen Tagish Lake on the B.C.-Yukon border brought Jim Brook, the lodge owner who found it an estimated $850,000. The University of Alberta, with Canada’s second-largest meteorite collection, bought most of the meteorite. For sample meteorite pricing, see http://www.meteorlab.com/METEORLAB2001dev/offering21o.htm
The Washington University in St. Louis has a great webpage showing all sorts of meteorites at http://meteorites.wustl.edu/id/metal2.htm.
If you do find a possible meteorite, send a photo to Dr. Hildebrand. Note that American Meteor hunters have to report to the Canadian Customs, Canada has export restrictions on them.
[meteorite_flow_chart.gif]
Above is a flow chart guide designed by Deborah Guedes in Brazil to help identify a meteorite. http://www.lpi.usra.edu/meetings/metsoc2010/pdf/5357.pdf “Regmaglypts” are those worn-away thumb sized hollows in the surface.
The College meteor camera has seen large fireballs or bolides of over 100 kg that hit the ground about four times in the past six years. The last was:
– December 20, 2014 over Canal Flats, BC hitting by Marconi Peak on White Swan Lake road. This was possibly a rare carbonaceous chondrite.
– September 26, 2011 over Banff, AB, hitting in the park.
– May 14, 2011 over Creston, BC, hitting by Duck Lake.
With shared videos from other ground stations in the BC Meteor network, like West Kelowna, Penticton, Courtney, Vancouver or Prince George, we can triangulate where these have impacted to within 2 or 3 kilometers. We then have a chance to find these rare meteorites and to find out what they contain.
College of the Rockies also belongs to the Sandia National Laboratory North American meteor network, and we upload videos of fireballs to there.”
Rick Nowell
Astronomy Lab Tech
College of the Rockies