Location: Chemistry/Physics Building, MUN
Time: 8:00 pm
Fred noted the latest National Journal issue had an article on how Edmund Halley was never actually knighted. When we hosted the GA in 2004, we recreated Halley's landing in Newfoundland. Its just as well the plaque we had created for display at Memorial University has disappeared.
Ben Llewellyn has donated two books. They were from the Time-Life series, one entitled "UFOs" and the other "Time and Space". We would like to thank Ben for all the books he has donated.
Chris noted we have received a gift from the Edmonton Centre of a book called "The Meteorites of Alberta", by A.J. White. This was an interesting book that Chris very quickly showed to us.
Phil is with the University of Western Ontario.
Phil's take home message is that he found this event, in particular, reminded him that a meteor fall seems to touch people in ways that other scientific events don't. People seem to immediately appreciate the connection with the sky.
Phil emphasized that the work to study a fall such as this requires many people. He showed us some of the many people involved. Dr. Peter Brown was the lead scientist to study the fireball. Phil was the lead scientist to study the meteorite.
The fireball was discovered by the Southern Ontario Meteor Network (SOMN). It entered the atmosphere at an altitude of 100km over Guelph, travelling at 20km/s. The track ended near Grimsby at 20km in altitude. Most meteors break apart or vanish at 50km in altitude, only something like a fireball gets to 30km, and even more rarely to 20km. It was thought it started at the size of a tricycle, and may have left masses that could total several kilograms.
All seven cameras saw the fireball, and Phil showed us the videos, including a beautiful one where it went straight overhead.
There were many witnesses, and the Meteor group talked with many of them. The group was particularly interested in those who heard noises, including crashes or thuds! Sonic booms were also of interest. Many people hear a noise like bacon sizzling. This is not well understood, since the meteor may be far away at the time. The group heard from a few of these.
The goldmine of positional information allowed a determination of the orbit. The orbit is inclined 20 degrees above the ecliptic, and the final plunge was at a steep 60 degree angle. Of the 35,000 officially described meteorites, only 12 have known orbits (all the inclinations vary).
One person managed to take a shot of the fireball with their camera. This was remarkable, as usually the only pictures (apart from survey cameras) come from security cameras.
The meteor had a terminal burst. The videos indicated four or more fragments. The speed of deceleration of the fragments, combined with meteor radar (SOMN supports the radar network), and the infrasound data, indicated around 10kg of material may have made it to the ground. This is so far the most instrumented fireball event known!
The group put out a public call for help with the search. Phil related how the ground search was undertaken. They also heard from several land owners, including one group of people where a meteorite had nearly smashed the windshield of their SUV, bounced on the hood of the SUV, and then but a ding in their garage door! They found it odd someone would paint a rock black and throw it straight up and down over their vehicle! Fortunately, the announcements made them think of the possibility of a meteorite. One place the group searched was in a greenhouse with a broken window, but no luck was to be had! A few professional searchers did manage to find some pieces. Luckily, most of the SUV fragments were put aside under the protection of an eave, so they were protected from the effects of too much sunlight and rain. They were fairly well preserved.
A new instrument was used that only a few in the world have been able to interpret: doppler radar. This radar responds to hail. Two minutes after the event, a radar in Buffalo got a return of about 5 square km in the expected area where fine particles would fall (and be blown by the wind). This confirmed the group's track, plus their determination of where the fall would be.
Some small pieces were found by using magnets attached to ATVs (some people do this for a living to remove nails, apparently).
Phil described fragment #5. They could find out a lot by using X-ray diffraction, and X-ray Micro Computed Tomography, and not damage the sample in any way. With tomography, a virtual slice can be made. There was another fragment (HP-1) that had a standard polished thin section made. You look at this with plane polarised light.
So far there are 13 fragments, totalling 215g. The meteorite appears to be an ordinary H5 chondrite.
After the talk there were some questions.
What was the total mass? Phil said from the brightness of 100x the full moon, and the velocity of 20km/s, they estimated about one metric tonne.
Did they think of looking in eavestroughing? Yes, but they were afraid of getting sued (unless someone looked completely on their own initiative). Some people did hear hail hit their roof, so it is a good idea.
What about searching in spring, when things may surface? They should have better ground contrast, and yes, the freeze and thaw cycle might cause some objects to work their way up from their pits in the ground.
How do the polarised colours in the slides of the thin, polished section come about? In short, the minerals will change the polarisation of the light. Phil explained a little about how two polarisers at right angles could cancel all the light, if it remained in one plane only.
Where was the main impact? It is thought to be Southeast of where they found the mid-range size fragments.
Why were there rust spots in the olivine? On the earth, or another big body, iron and silicates would get mixed together, and the iron would get bound up with other stuff, including oxygen. In a meteorite, the iron doesn't usually get mixed, remaining as elemental iron. This way, it can rust.
Phil was thanked for his talk. We gave him a shirt and one of the Society's Calendars to thank him for his efforts!
Richard (filling in for just this month) quickly went over the upcoming events. He passed around a sheet. Mars will be the main thing this month. Mercury will be visible in the morning. He also outlined what will be going on with Comets and other things this month. The sun has still remained pretty quiet. The ISS will have some good passes.
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