Meteorite-dropping fireball named after Sutter’s Mill

Great view of the interior of a 17.7 gram piece of Sutter's Mill meteorite. Credit: Larry Atkins

It’s official. The meteorites that peeled off the California fireball last month peppering the towns of Coloma and Lotus are named Sutter’s Mill after the famous locale where the California Gold Rush began. As of May 22, 49 fragments had been recovered with a total weight of 437 grams or 17 grams shy of one full pound.

Here are a few details from the Meteoritical Database:

Pinpoint and pinhead-sized bits of olivine and other materials inside my tiny specimen of Sutter's Mill. Magnified about 20x. Photo: Bob King

“A bright daytime east-to-west moving fireball was seen on April 22, 2012, from locations over California and Nevada between 7:51:10 and 7:51:30 am local daylight time (UT-7).

The meteoroid fragmented towards the end of its trajectory. A loud sonic boom was heard in a wide region around Lake Tahoe. Wind gusts were felt and houses shook. At least a kiloton of kinetic energy was released, based on the infrasound signal detected at two stations.”

Eye witnesses in the townships of Coloma and Lotus, El Dorado County, reported hearing whistling sounds and some smelled a “welding” odor. U.S. National Climatic Data Center’s “NEXRAD” Doppler weather radar sweeps detected the falling meteorites.”

“In data analyzed by Marc Fries of the Planetary Science Institute and Robert Matson of S.A.I.C., the radar-defined strewn field is centered on the Sutter’s Mill historic site. On April 24, Robert Ward searched under the radar footprint and collected the first 5.5 g meteorite in Henningsen-Lotus Park.” More details HERE.

Closeup of bubbly crust on a 3 mm-wide fragment of Sutter's Mill meteorite. 30x magnification. Photo: Bob King

Word soon circulated among the meteorite community that Sutter’s Mill was an unusual type of carbonaceous chondrite (car-bon-AY-shuss KON-drite).  These meteorites get their name from the carbon, water and sometimes organic compounds like amino acids they contain. Many of us were on tiptoes waiting for the final classification. Looks like we’re going to have a wait a bit longer.

Scientists were only willing to give it a preliminary “C” (for carbonaceous chondrite) until detailed studies at half a dozen labs are completed.

A week ago a very tiny bit of the meteorite made a second earthly journey straight into my mailbox. Under the microscope at 30x the interior is black as coal with only a few white crystalline flecks. What caught my eye was the crust. Finely stippled to the eye, the scope transforms the little bumps into a landscape of black bubbles that looks like a burnt marshmallow. You can even see where escaping gases punched tiny holes in the bubble tops. This “fusion crust” forms when the outer millimeter or two of the meteorite melts on entering the atmosphere at tens of thousands of miles per hour.

If you stay up past midnight you may find it hard to tear yourself away from the sight of the Milky Way spanning the eastern sky. This picture was taken Monday morning when I should have been sleeping. Details: 15mm lens at f/2.8, ISO 1600, 30-second exposure. Photo: Bob King

One thought on “Meteorite-dropping fireball named after Sutter’s Mill

  1. Hi Bob,

    Jim Woodell’s strewn field looks amazing similar to the map I made :) which is great! I wanted people to know where to look. Could you please call me at 303-731-9197 at your convenience? I would like to as you some friendly questions.

    Sincerely,
    Glenn Davis

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