Streaking through the Sky

09/30/2009

A new study investigates a century-old scientific mystery: Which direction did the asteroid that created the Barringer Meteorite Crater come from?

Imagine the moment before impact:  the sky was split with fire as a massive iron asteroid pierced the atmosphere and collided violently with the surface of the Earth. 

From what direction did this asteroid hurtle?  When standing on the rim of the crater, does one look to the north when trying to picture the event or in some other direction?

This question has vexed scientists for over one hundred years. Daniel Moreau Barringer was the first geologist to wrestle with this question.  He was impressed with the massive cliffs of the southern crater wall and suggested the impacting asteroid traveled from the north to the south to uplift those cliffs.  Other investigators have suggested nearly every other direction: to the east, to the northeast, to the north, and to the northwest.

A new study by Michael Poelchau, Thomas Kenkmann, and David Kring tried new techniques to unravel this mystery.  They searched for wedges of rock that were thrust into the walls of the crater during the uplift of the crater rim and examined that uplifted rim for asymmetries that might point to the trajectory of the impacting asteroid.  As with past efforts, the picture the data painted is murky.  Wedges of rock thrust into the upper crater wall occur on the northeast to northwest sides of the crater, favoring an impact in that direction.  On the other hand, several other indicators point in nearly the opposite direction, from the NNW to the SSE.  These data include a dramatic uplift of bedrock in southeast corner of the crater.  Although it is not the highest point around the crater rim today, the stratigraphic uplift of bedrock in that area of the crater is the largest.

This study, like a recent study by Senthil Kumar greatly helps us understand the fracturing, excavation flow, and uplift of rock around the crater during an impact.  It also, however, still leaves us wondering where to trace the iron asteroid as it streaked through Earth’s sky.