NASA scientists will venture into an isolated part of the Bolivian Amazon to try
and uncover the origin of a 5 mile (8 kilometer) diameter crater there known as
the Iturralde Crater. Traveling to this inhospitable forest setting, the
Iturralde Crater Expedition 2002 will seek to determine if the unusual circular
crater was created by a meteor or comet.
The team intends to collect and analyze rocks and soil, look for glass particles
that develop from meteor impacts and study magnetic properties in the area to
determine if the Iturralde site, discovered in the mid-1980s with satellite
imagery, was indeed created by a meteor.
If a meteorite is responsible for the impression, rocks in the area will have
shock features that do not develop under normal geological circumstances. The
team will also look for glass particles, which develop from the high
temperatures of impact.
The Iturralde Crater Expedition 2002 team will extensively analyze soil in the
impact zone for confirmation of an impact. One unique aspect of the Iturralde
site is the 4-5 km deep surface sediment above the bedrock. Thus the impact was
more of a gigantic “splat” rather than a collision into bedrock.
The large crater is only 1 meter lower in elevation than the surrounding area.
Water collects within the depression, but not on the rim of the crater, which is
slightly higher than both the surrounding landscape and the interior of the
crater. These subtle differences in drainage are reflected in the forest and
grassland habitats that developed on the landscape. It is precisely these
differences in the vegetation structure that can be observed from space and
which led to the identification of the Iturralde Crater from Landsat Images.
Compare these images with topographic data from the Shuttle Radar Topography Mission.
Germany’s Ries Crater (or Nördlinger Ries) is not easily discerned in space-based images. The crater’s existence was probably just as subtle to the medieval Europeans who established a settlement inside it and unknowingly matched their 1-kilometer- (0.6-mile-) wide city to the likely diameter of the meteorite that formed the crater.
Wolfe Creek Crater is the second largest crater in the world from which meteorite fragments have been collected. Because of its excellent preservation, the crater clearly shows the classic features that result from a large meteorite striking the Earth.
Deep in the Sahara Desert lies a crater. Nearly a perfect circle, it is 1.9 kilometers (1.2 miles) wide, and sports a rim 100 meters (330 feet) high. Modern geologists long debated what caused this crater, some of them favoring a volcano. But closer examination of the structure revealed that the crater’s hardened “lava” was actually rock that had melted from a meteorite impact.