SUMMARY

SUMMARY

This meteorite fall was an evening fireball that occurred at 10:47 PM local time on 23 October 2015, or 24 Oct 2015 0547 UTC. The fireball was prominent and 218 eyewitnesses reported it to the American Meteor Society, almost exclusively across California. Fourteen credible eyewitnesses from around Paso Robles to San Luis Obispo, CA and points nearby reported hearing sonic booms from the falling meteorites.

Meteorites have been recovered from this event.

This event is recorded as American Meteor Society event number 2635 for 2015. Signatures of falling meteorites can be found in imagery from four nearby weather radars. In the NEXRAD weather radar network operated by NOAA, the KVTX (Los Angeles, CA), KVBX (Vandenberg AFB, CA), KHNX (San Joaquin Valley, CA) and KMUX (San Francisco, CA) radars record signatures of falling meteorites.

The first appearance of falling meteorites on radar occurs at 05:49:10 UTC and 16,460 m above sea level (ASL) in the 0539 UTC data set for the KVTX radar in the 4.5 degree elevation radar sweep. Signatures consistent with falling meteorites appear in a total of six radar sweeps from the two radars, with a final signature appearing at 06:00:03 UTC.

Calculations of mass and total number of meteorites based on weather radar data indicate that this meteorite fall is approximately 1.7x the total mass of the Park Forest, IL meteorite fall in 2003. The fragmentation behavior of the Creston fall is anomalous for an average meteorite, based on comparison with other meteorite falls seen in weather radar data. The Creston meteorite fragmented extensively, leaving relatively few large meteorites and most of the fall mass occurs as small meteorites. There are a few possible explanations for this, as the parent meteoroid may have been fragile due to a significant impact while it was still in space, it may have been composed of poorly-compacted material from an asteroid surface (a “regolith breccia”), or it may have shattered due to some feature of its infall such as a steep infall angle or high speed. At present, none of these hypotheses is the favorable answer.

Meteorites recovered from this event have been classified by the Meteoritical Society as an L6 chondrite.

Surprisingly, the Creston fall occurred about a half hour after another significant fireball, this one occurring only about 350 km (~220 miles) to the east. The American Meteor Society report for that event is number 2697 for 2015, and features 111 eyewitness reports. To date no meteorites have been recovered from this event.