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Gao-Guenie Meteorite(s): Change is a constant in meteorite science. Get ready for more!

Gao-Guenie is a fall from March 5, 1960 that once was thought to be two separate falls. The first appearance of Gao in the Meteoritical Bulletin was in 1967 while Guenie showed up in 1980. And then Gao-Guenie landed on the scene in the 1999 Meteoritical, formally changing the situation for all previous Gao and Guenie owners.

According to the Meteoritical Bulletin, no. 83:

Gao-Guenie, new name With the recent paper by Bourot-Denise et al. (1998), the Meteorite Nomenclature Committee has decided that a new, collective name, Gao-Guenie, will be bestowed upon all meteorites formerly identified as either Gao (Upper Volta) (frequently truncated to Gao) or Guenie. It had been reported that two meteorite showers occurred one month apart in 1960 in the country now known as Burkina Faso. But the new work confirms long-held suspicions that the two meteorites are indistinguishable from each other and that there was most likely only one fall (1960 March 5). The confusion about this meteorite has been compounded by the fact that new stones continue to be found ~40 years after the fall and are given arbitrarily one or the other name. Henceforth, the official name for all meteorites from this shower will be Gao-Guenie, with the names Gao (Upper Volta) and Guenie as recognized synonyms.

The other day I was digging through some stored meteorites and discovered my complete individual of Gao-Guenie. I didn’t have it displayed anywhere and had completely forgotten what it looked like. It was a very pleasant surprise because its color and form were better than I recalled. Further, it seemed larger than I remembered.

As an H5 chondrite, Gao-Guenie ranks high in the ordinary part of ordinary chondrites. However, the events of the fall of Gao-Guenie include a deafening sound that could be heard up to 100km away when thousands of stones crashed to earth and through a few hen houses as well.

What makes meteorite collecting exciting to me, as most of you know, is when a particular meteorite lands at the intersection of being a witnessed fall (the older, the better), is scientifically interesting, and involves some aspects of human culture or reaction. Gao-Guenie fits this bill in several ways. Although calling Gao-Guenie a historical fall might be a stretch, it is over 60 years old meaning its age can be noted as a reasonable proportion of a century.

As a witnessed fall, almost all boxes are checked. The only uncertainty is the exact time of fall, but a listed “about 1700 hours” is plenty good enough for me. But the win here is a sub-intersection between culture and science. The cultural aspect is found in the event that two supposedly distinct meteorites became one. I remember when Gao was Gao, and Guenie was Guenie. Yes, they looked much the same, but the price per gram was usually higher for Guenie because there seemed to be less collection material to go around. But honestly, I think most of us had our doubts about their individuality. There were just too many coincidences to ignore.

When collecting meteorites, some flexibility is needed given that science must be able to change. And that includes the materials science is studying. Like dinosaurs, meteorites have changed names, changed classifications, and even fallen out of being actual meteorites. But as scientific instrumentation and space science evolves, meteorites have also changed origin stories, they have changed their importance in particular studies, and they have changed in total known weight. And now that we have actual rock samples returned from an asteroid, and another space mission named Psyche on its way to study a metal rich asteroid named Psyche, expect many more changes in our understanding and interpretation of particular meteorites.

The race is now on to match the stones in our collections with the Asteroid Bennu from which the OSIRIS-REx mission just delivered an abundance of material. I have full confidence that when the asteroid material is formally studied, there will be many discoveries that directly affect the specimens in our meteorite collections. But on a side note, in celebration of the OSIRIS-REx sample return accomplishment, I am reading the 2019 book The Andromeda Strain Evolution.

Until next time….

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