The large annular lake in this image represents the remnants
of one of the largest impact craters still preserved on the
surface of the Earth. Lake Manicouagan in northern Quebec, Canada,
surrounds the central uplift of the impact structure, which is
about 70 kilometers in diameter and is composed of impact-brecciated
rock. Glaciation and other erosional processes have reduced the
extent of the crater, with the original diameter estimated
at about 100 kilometers. This natural-color image of the region
was acquired by MISR's nadir (vertical-viewing) camera on
June 1, 2001, during Terra orbit 7737.
The impact that formed Manicouagan is thought to have occurred
about 212 million years ago, toward the end of the Triassic period.
Some scientists believe that this impact may have been responsible
for a mass extinction associated with the loss of roughly 60% of
all species. It has been proposed that the impact was created by
an asteroid with a diameter of about 5 kilometers. The lake is
bounded by erosion-resistant metamorphic and igneous rocks, and
shock metamorphic effects are abundant in the target rocks of the
crater floor. Today Lake Manicouagan serves as a reservoir and
is one of Quebec's most important regions for Atlantic salmon
fishing.
MISR was built and is managed by NASA's Jet Propulsion Laboratory,
Pasadena, CA, for NASA's Office of Earth Science, Washington, DC.
The Terra satellite is managed by NASA's Goddard Space Flight Center,
Greenbelt, MD. JPL is a division of the California Institute of
Technology.
Image credit: NASA/GSFC/LaRC/JPL, MISR Team.
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