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The Johnstown Diogenite Meteorite Turns 100! Party in Colorado on July 6th!

 

“With the visible stars revolve stones which are invisible, and for that reason nameless. They often fall on the ground and are extinguished, like the stone star that came down on fire at Aegospotami.”     -Diogenes of Apollonia

 

Back in 1924, July 6th at 1620 local time to be exact, a monomict brecciate diogenite of some 40kg fell from space with part of it landing in a cemetery near an active funeral service. 

 

A day after the fall, the local newspaper, the Reporter-Herald contained the following description, “With the rumble of a distant battle and the flare of a star shell a meteor streaked across the sky.”

The July 8, 1924 Fort Collins Express-Courier newspaper described the fall of Johnstown with, “Staccato cracks like the noise of a machine gun” as the “visitor” hurled through the atmosphere, breaking up an Elwell baseball game “in a stampede.”

And more recently, Ardis Briggs, a historical society volunteer was quoted in a 2014 article in the Loveland Reporter-Herald, “Anyone who saw it is of course passed away by now. But we have some accounts from some people who were children. Some people thought it was the end of the world because it smelled like sulfur and the loud sonic boom.”

Johnstown is a beautiful meteorite with emerald green pyroxine crystals in a milky white matrix. Diogenites are known for ranking low on the durability scale. In fact two of Johnstown’s siblings, Tatahouine and Shalka, reside in collections mostly as small fragments where individual collectable specimens more than a few grams are fairly rare. And yes, the Star Wars home planet of Luke Skywalker is named Tatooine after the location the diogenite fell, and also that Tatahouine, Tunisia was a filming location for the movie.

From my perspective as a collector of historical witnessed meteorite falls, Johnstown has it all. Plenty of witnesses, a fast recovery, unusual stories, great press coverage, and the meteorite is a member of a rare group of achondrites likely originating from the subsurface of asteroid 4 Vesta. And now that Johnstown is a centenarian, it is undeniably historically old too.

A current model for members of the HED group meteorites indicate that not only is Johnstown from the asteroid 4 Vesta, but likely from deep inside the mantle of the asteroid with the eucrites being from near or at the surface, and howardites being a mix of eucrite and diogenite material. Growing up well insulated inside the asteroid, Johnstown and the other diogenites cooled slow enough to allow larger crystal growth similar to rock candy forming out of supersaturated sugar water. Presumably, being a differentiated asteroid, 4 Vesta should also have a core likely of nickel iron and possibly a core-mantle boundary containing material represented in our meteorite collections by pallasites. Not a bad gig for 4 Vesta, an asteroid named after the Roman goddess of the hearth and household. And not a bad guess for Diogenes of Apollonia for whom the diogenite meteorites are named because he is credited with the first suggestion that meteorites came from space (see quote at top).

Vesta and another asteroid you may have heard of, Ceres, were explored remotely by the Dawn spacecraft. In a break from traditional NASA acronym mission naming, the name Dawn was a nod to the Dawn of the Solar System where asteroids represent primitive remnants from the birth of our solar system that have changed far less over time compared to the full sized planets. I added the “full sized” qualifier because Ceres, which comprises a quarter of the mass of the entire asteroid belt, is considered a dwarf planet, and the only one within the inner solar system at a mere 2.8 AU from the sun.

 

Back on earth, the town of Johnstown has not forgotten about their unlikely visitor, and celebrations are planned this summer on and around July 6. There is an effort by the Johnstown Historical Society to raise money in order to purchase a piece of the Johnstown diogenite meteorite that would then retire out its existence as a full-time resident of Johnstown living in the local museum much the same way Ensisheim is now the most famous resident of, well, Ensisheim. Donations over $20 to the Johnstown meteorite fund  will, according to the website, receive a small keepsake token. Another Johnstown City website appears to have meteorite plans for this summer as well.

Of the 520 records for Diogenite (not including diogenite-pm classifications) in the Meteoritical Bulletin, only nine are witnessed falls. Johnstown lands right in the middle of the nine being the fifth witnessed fall of a diogenite. If one drills down on the dates of those nine falls, some oddly interesting coincidences appear. One thing to notice is there seems to be some clustering of the falls given the 181 years since the first witnessed fall of a diogenite.  Four fell within the 28 years between 1843 and 1871. And three fell in the seven years between 1924 and 1931. And if that isn’t already interesting, two fell one year apart in 1870 and 1871, and two more fell one year apart in 1924 and 1925! The pair of falls in the 1800s are listed with one fall in the spring and the other in June. The pair in the 1920s have one fall in July, and the other in August. Sixty-eight years would pass before another witnessed fall of a diogenite would be recorded in 1999. The most recent, next and last diogenite fall was in 2016.

Of course a vast majority of diogenites that fall to earth are never witnessed with most of them landing in water and many of the remaining, even if witnessed flying through the air, were considered little more than curiosities from the sky and never investigated further.

 

 

Throughout this article are images of my piece of Johnstown heaven. A crusted quarter slice of 80 grams, that I received in an institution trade some twenty years ago.  I’ve been waiting patiently for two decades in order to celebrate the 100th Anniversary of Johnstown, and if I can squeeze in a visit to Johnstown, Colorado on the 6th of July, I will.

Until next time….

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