Meteorite Strikes Peru: Geologists rush to study the crater and pieces left behind
Article by Lionel E. Jackson Jr., Peter Brown, Jay Melosh and Dolores Hill from Geotimes
Synopsis and resource annotations by Max Grinnell
When something falls out of the sky, what happens? It is a question that has
puzzled scientists for decades, and while many objects strike the earth's
surface (thereby becoming a meteorite), three-quarters of them touch down in
open water. In 2007, a meteorite landed in Carancas, Peru and the landing
presented some rather unique opportunities for geologists.
In the July 2008 issue of Geotimes, scientists Lionel E. Jackson Jr., Peter
Brown, Jay Melosh and Dolores Hill offered their own account of this meteorite
strike in Peru, the crater it created, and the ensuing buzz of scientific
activity. It all started on the morning of September 15, 2007 when a bright
fireball moved across the sky over Lake Titicaca. Upon final impact a few
seconds later, eyewitnesses noted that the meteorite had left a 13.5 meter wide
crater, and that fragments of the meteorite landed as far away as 200 meters.
The meteorite presented a rather compelling and fairly unique situation for
scientists all over the world. It was the chance to study fragments of a fresh
impact crater and to take a close look at a chondrite. A chondrite is a stony
meteorite that generally breaks up in the atmosphere; the largest intact
chondrite to reach the Earth's surface was during the Jilin, China meteorite
shower in 1976.
The scientists moved quickly and began working with Peru's geological survey
team on examining the meteorite. One of the survey members, Luisa Macedo, was
able to cut the impact samples into thin, polished sections which under a
microscope revealed that the meteorite was in fact a chondrite. The Lunar and
Planetary Laboratory at the University of Arizona later confirmed this finding,
and scientists have also been able to determine the meteorite's velocity, mass,
and impact angle.
One puzzle remained as scientists continued to research the meteorite and its
impact site. Why did this object create a round crater? This was a particularly
vexing question, as the meteorite had entered the atmosphere at an acute angle.
In most cases an acute impact angle would create an elliptically-shaped crater,
but that was not the case here. Scientists eventually drew on information from
other fields to determine that at such high speeds the resulting crater is
created by a massive explosion. With that in mind, such variables as angle of
approach and size cease to be of much importance in determining the final crater
Found below is a list of useful resources that will illuminate and
enhance understanding of the topics found within this article.
The first three links are broadly related to the world of meteorites, and the
second group is related to geology.
The first link
take interested parties to Washington University's Lunar Meteorites website,
which contains some basics on the world of meteorites, including answers to
questions such as "How are lunar meteorites classified?"
The second link
to a NASA news commentary from David Morrison on evidence that suggests that a
massive impact triggered the Permian-Triassic extinction.
the third link
the homepage of the Association of Lunar and Planetary Observers. This site also
has some good information on meteorites, along with sections dedicated to
Jupiter, Saturn, and a sample of minor planets.
The fourth link
to the OpenCourseWare page for an introductory geology course at MIT taught by
Professor Lindy Elkins-Tanton. The site includes lecture notes, a syllabus,
assignments, and other course materials.
The fifth link
an interactive resource on the Earth's interior, created by the people at the
Annenberg Media project.
The last link
an excellent series of teaching activities related to structural geology created
by a team at the earth sciences department at the University of Leeds.
Overall, these resources should provide greater scope and help contextualize the
ideas and concepts found within in the featured work. The list provides links to
resource records in the Applied Math and Science Education Repository