Archive for the ‘Campo del Cielo’ Category

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Meteorite show-and-tell at the PVAA September meeting

September 22, 2018

Last night was the September general meeting of the Pomona Valley Amateur Astronomers. Instead of having an outside speaker, we had meteorite show-and-tell. Members brought their personal collections of meteorites and impactites, or talked about their history with meteor-hunting, or both.

We kicked off with a short talk by Dr. Eldred Tubbs, who told us about his experiences working with the Prairie Meteorite Network when he was on sabbatical from Harvey Mudd in 1969-1970. The Prairie Meteorite Network was a program run by the Smithsonian Astrophysical Observatory between 1964 and 1975, which used a series of wide-format cameras scattered across the Midwest and Great Plains to capture images of bright meteors, in hopes of locating the resulting meteorites. In ten years of operation, the Prairie Meteorite Network only discovered one meteorite fall, the Lost City meteorite from just outside of Lost City in eastern Oklahoma.

We then proceeded more or less by size of collection. Our club secretary, Ken Elchert, only has one meteorite-related specimen, but it’s a doozy: a massive bilobed indochinite tektite the size of a small pastry. This blob of glass solidified in the atmosphere from molten material blasted out of a huge impact in southeast Asia about 700,000 years ago. I love tektites–externally they resemble black rock, like basalt, but in fact they are glass, so they only weigh about half as much as you might expect when you pick them up. Ken’s specimen, obtained from a gem and mineral show a few years ago, was easily the biggest tektite I’d ever gotten to see firsthand or touch.

Gary Thompson, our club treasurer, was up next. He presented two small meteorite specimens in nice cases. You can see them on the right side of the photo above, surrounded by books. I wasn’t taking careful notes so I don’t remember the details on the second, but the first, in the larger, wooden box, is a piece of an observed fall from 1918 in Russia.

Laura Jaoui was up next. She has an extensive collection of small specimens, including fragments of lunar and Martian meteorites and a couple of small pieces of the Chelyabinsk meteor that exploded over Russia in 2013. Laura also had a lot of cut and etched pieces to show the internal structure of meteorites, especially the beautiful Widmanstätten patterns inside iron meteorites. She had thoughtfully included a variety of magnifying glasses, jewelers’ loupes, and magnets for investigating the structure and properties of the samples in her collection.

I was next up, with my little collection. I haven’t blogged about all of them yet. The Middlesborough meteorite is not the original–that’s on display at the Yorkshire Museum. My copy is a cast that I obtained this spring, which fired my interest in oriented meteorites. I hadn’t known that such things existed, and I spent a few evenings educating myself about them. I put the results of my research into a slideshow, which I gave for the club late this spring, and later turned into the photo book shown here with my meteorites. In the time since I blogged here about my pieces of Campo del Cielo and Sikhote-Alin I’ve obtained additional, smaller representatives of both falls. The NWA Saharan chondrite I got on eBay earlier this year, and the tiny fleck of Canyon Diablo is from the gift shop at Meteor Crater. I picked up the moldavite in the center at a rock shop in Arizona last year. I do intend to blog about all of these things in time.

The anchor of the evening and the star of the show was Jeff Schroeder’s collection. Jeff has been finding, collecting, classifying, and working with meteorites since the 1970s, and he’s worked with some of the pioneering SoCal meteorite hunters. Almost everything on the long table in the above photos is his, and that’s only a fraction of his collection. Jeff gave us a wonderful talk on the history of the collection–much of which is bound for local universities in time–and on the histories of the specimens themselves, and what they tell us about the history of the solar system.

All in all, it was a great evening, with lots of great specimens and inspiring conversations. We should do more things like it in the future. The 50th anniversaries of the Apollo missions are coming up, and we’re planning to have members give short talks about each manned Apollo mission in the month of its 50th anniversary. But we should have a night next year just for people to bring their memorabilia of the space program. We have a lot of retired aerospace engineers in the club, including people who worked on the Apollo missions and the Space Shuttle. It would be great to hear about these things firsthand.

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My meteorites: Campo del Cielo (40g)

April 25, 2018

My recent talk on impacts and the end-Cretaceous extinctions reminded me that I’ve never posted about my meteorite collection. It’s not a large collection, just a handful of things I’ve picked up, but each is satisfying in its own way.

This is the first meteorite I ever owned, a 40g piece of Campo del Cielo from Argentina. It’s about the size of the last joint of your index finger. Following the universal standard for meteorite photography, the scale cube in the photos is 1cm.

I picked this up probably 15 years ago at an auction at a Society of Vertebrate Paleontology annual meeting. I don’t remember the year – early 2000s for sure. The meteorite came with a little drawstring bag made of red felt, and a certificate of authenticity. It was clearly marked as a chunk of Campo del Cielo, which fell over northwest Argentina four or five thousand years ago.

The original Campo del Cielo meteor exploded in the atmosphere, much like the Chelyabinsk meteor over Russia in 2013, but on a much grander scale. The Chelyabinsk meteor is estimated to have been 20m in diameter, and it produced an airburst of approximately 500 kilotons. The Campo del Cielo meteor was probably more like 50m in diameter, so it would have been a multi-megaton explosion in the upper atmosphere. The resulting strewn field is 2 miles wide, more than 11 miles long, and includes at least 26 craters with diameters of up to 100 meters; the impact of the fragment that produced the 100-meter crater would itself have been multi-kiloton event.

I didn’t know any of that at the time I got the meteorite at the auction. I vividly remember how much I paid for it: $80. I remember so clearly because I almost instantly regretted it. I don’t know who I was talking to afterward, but someone looked at the meteorite and commented that it would be easy to fake with a bit of iron slag. That seemed plausible – it didn’t look like any meteorite I’d seen pictures of, so I assumed the chance that it was a fake was high. I had other fish to fry at the time, being a new dad and halfway through a dissertation, so I never did any research to see if the meteorite was real or fake. I kept it, but I never put it on display, and over the years I sort of lost track of it.

I rediscovered it this January during a major bout of house-cleaning. It’s funny, in the time between when I obtained this piece and now, I’ve looked at so many meteorite photos that I can just glance at this and think, “Yep, it’s a Campo”. Five minutes of image searching for Campo del Cielo pieces will turn up many authenticated examples with the same general appearance, like angular chewed gum with fracture lines and surface pitting. Campo del Cielo is one of the least expensive meteorites to obtain, with prices around $1/gram still being pretty common. (So in fact I overpaid a bit back when I got this, but since it was an auction to support the society I don’t mind.) With such distinctive morphology and such low prices, it’s probably much less expensive to simply buy a real piece of Campo than to fake one, especially at small sizes.

So even though it is one of the smallest pieces in my collection, this little gem means a lot to me. It tells two stories: one about my personal journey from interested-but-ignorant space enthusiast to semi-knowledgeable, semi-professional astronomy writer – and one about a 65,000-ton chunk of iron from the core of a shattered planetoid, which exploded with the force of an entire nuclear arsenal and showered a vast area with what must have been a lethal rain of shrapnel, from pea-sized up to house-sized. Including this little piece, cosmic voyager and witness to awesome forces of creation and destruction.

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If you’re interested in obtaining a meteorite or starting a collection, I have two pieces of advice. The first is, buy from reputable dealers. Many honest dealers are members of the International Meteorite Collections Association and will list their IMCA member number wherever they do business. There are good dealers who are not IMCA members for various reasons – some just don’t like clubs and the politics that sometimes comes along with membership – but it’s a start. Also check seller feedback if you buy from online markets like eBay. And use search tools to do quick checks on individual dealers; the meteorite collecting community is pretty vigilant about detecting and outing bad actors.

The second and probably more important guideline is to educate yourself. Spend a week of evenings looking through websites and online ads and learning to know what to look for in genuine meteors. It’s not completely foolproof – a few unscrupulous people will pick up bits of inexpensive recent falls and try to pass them off as examples of rare and valuable historical meteorites, for example – but at least you’ll develop the knowledge to tell genuine meteorites from “meteorwrongs”. Good hunting!