When you walk into the rocks and minerals section of the ROM, you probably wouldn’t look twice at the dull grey, brown and black rocks on display on the far left wall—there are just so many beautiful, colourful rocks to see. But don’t be fooled by their bland appearance; these rocks are probably some of the most interesting to study and are a part of the ROM’s expansive and diverse meteorite collection.
The ROM houses the rarest meteorites in the world, including the Tagish Lake meteorite (the most well-preserved meteorite ever found), a Martian meteorite (a piece of Mars) and a lunar meteorite.
“They’re really growing their collection and I’d say that they have one of the best in the world—definitely in the top 10—[and it’s] probably the best place in Canada to study meteorites,” says U of T PhD candidate Katrina van Drongelen.
A meteorite’s chemical composition preserves information about the creation and evolution of the solar system, some 4.6 billion years ago. The three main types of meteorite—iron, stony-iron, and stony—are made of iron-nickel metal, iron-nickel metal and silicate, and silicate minerals respectively.
Van Drongelen has been working closely with the ROM’s collection since she started her Master’s degree in Geology a year ago and will continue to work with the collection for her PhD.
For her Master’s research, van Drongelen studied an ordinary chondrite—a stony meteorite that has been well-preserved for billions of years. The meteorite was thought to be from a meteorite fall that occurred in North-West Africa. After observing the chrondite using microscopes and various measurement techniques, she determined that the ordinary chondrite was not from that particular strewn field (a meteorite fall in which many pieces break off a single asteroid and fall to the ground).
“Initially, I just looked at it. Then, I took a slice off it with a wire saw,” van Drongelen explains. “I got some thin sections made for the microscope [slides]. I use a petrographic microscope, a microscope with different filters and lenses. That helped me classify it by looking at the amount of metal, for example, because eucrites [the general term for a stony meteorite] often contain a mixture of metal and iron. This one had about five per cent nickel-iron metal, about five per cent sulphite [pyrite] and a lot of silicate material [granite]. Looking at the different textures and components under the microscope helped me determine that it was an ordinary chondrite.”
Van Drongelen divides her time between the ROM’s petrographic microscope and the electron microscope at U of T, carrying samples of the meteorite with her back to U of T. For her doctoral thesis, van Drongelen is studying a completely different meteorite—essentially, the polar opposite of the one she observed for her graduate degree. The new meteorite is an A-chondrite, which unlike the ordinary chondrite, does not contain any early solar system material.
This rock resembles lava in that the heavier material has sunk toward the center while the lighter material it contained rose to the surface causing layering to occur. The A-chrondrite has metamorphosed over time, unlike the ordinary chrondite, which was extremely well-preserved.
The major differences between the two meteorites demonstrate the breadth of the ROM’s collection.
Van Drongelen considers herself very lucky to be working with this remarkable collection. While completing her Bachelor’s degree at the University of Manitoba, she received only a 30-gram sample, which is the typical size a student gets to work with. However, thanks to the ROM, van Drongelen was able to work with considerably larger samples; for her Master’s she worked with a 7.5-kilogram sample, and for her PhD she is working with a sample that is over 18 kilograms.
“[Working] with a small sample isn’t really accurate—you don’t get the whole picture. Trying to figure out what the whole meteorite is and then trying to extrapolate it to maybe an asteroid with a 30-gram sample is a big reach. The composition [and nomenclature] would have been slightly different if I hadn’t looked at it as a whole, just because it was so heterogeneous.”
Meteorite collector and enthusiast David Gregory has managed to obtain some of the rarest meteorites, which he generously donated to the ROM. David’s passion for meteorites started at the ROM, where he was first introduced to them. He’s been giving back to the collection in hope that others can obtain the same enjoyment he does out of them. “Almost every time he visits the ROM he comes with his briefcase and pours more meteorites out,” explains van Drongelen.
“If I was at another university, I would have one sample or a piece of a sample on loan from another collection and I wouldn’t be able to compare it to other materials. I wouldn’t have the opportunity to have easy access to a huge collection, so I wouldn’t be able to just walk up to a drawer, pick up two meteorites and hold them side by side to compare them. That’s the amazing opportunity I get at the ROM that I wouldn’t get anywhere else in Canada.”