Last night I found myself sitting at a restaurant with astronomers for the occasion of viewing a meteorite. Customarily, a few observatory folk have dinner with the speaker and then we go to the observatory for a public star night. While waiting for our entrees we passed the object carefully amongst ourselves, cherishing a few moments of close contact with this rare object.

Astronomers seem to be prone to public displays of humility. I would estimate that the humility quotient was near 0.8 (8 out of 10 Sagans- the Sagan is the international unit of humility). It is generally agreed that the Buddha achieved a Sagan quotient of unity. Okay, I’m kidding.

The curious 936 gram achondrite is from the recent Berthoud, Colorado, fall.  Meteor enthusiasts refer to the arrival of a meteorite as a “fall”.  This is one of only 5 witnessed falls in Colorado. A section of the meteor has been cut off and has been the subject of investigation at the University of Arizona.

Based on the composition of the object (olivine, plagioclase, ilmenite, chromite) and based on the reflectance spectra of various asteroids, the Berthoud meteorite is thought to be a fragment of the asteroid Vesta. Imagery of Vesta suggests that a portion of this object may have been shattered by an impact in the past.

The family whose property the stone landed on are somewhat bewildered by the event. They have been the subject of much unwanted attention, so the object is kept secure at an unknown location. In October of 2004, in the early afternoon several family members were standing outside their home when they heard a whistling sound and thump. Following the direction of the sound, they found the impact site less than 100 feet from where they were standing and in a spot where one member had just walked through. Only a small part of the object protruded upward through the disturbed topsoil.

Reportedly, it was cool to the touch immediately after arrival. This is counter-intuitive given the fiery appearance of most meteors. However, the object was quite cold prior to entry into the atmosphere and the rapid transit through the air didn’t allow for heat saturation. And, ablation carries away much of the friction energy.

The low iron object has a dark fusion crust over a grey, mottled composition. Other than the crust, it is not that unusual in its appearance. 

 

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