Mars Global Surveyor
Mars Orbiter Camera
Small Impact Craters with Dark Ejecta Deposits
MGS MOC Release No. MOC2-96, 18 March 1999
When a meteor impacts a planetary surface, it creates a blast
very much like a bomb explosion. Shown here are two excellent
examples of small impact craters on the martian surface. Each has a
dark-toned deposit of material that was blown out of the crater (that
is, ejected) during the impact. Materials comprising these deposits
are called ejecta. The ejecta here is darker than the
surrounding substrate because each crater-forming blast broke
through the upper, brighter surface material and penetrated to a layer
of darker material beneath. This darker material was then blown out
onto the surface in the radial pattern seen here.
The fact that impact craters can penetrate and
expose material from beneath the upper surface of a planet is very
useful for geologists trying to determine the nature and composition
of the martian subsurface. The scene shown here is illuminated from
the upper left and covers an area 1.1 km (0.7 mi) wide by 1.4 km (0.9 mi).
The larger crater has a diameter of about 89 meters (97 yards), the
smaller crater is about 36 meters (39 yards) across. The picture is located
in Terra Meridiani and was taken by
the Mars Global Surveyor Mars Orbiter Camera.
Malin Space Science Systems and the California Institute of
Technology built the MOC using spare hardware from the Mars Observer
mission. MSSS operates the camera from its facilities in San Diego,
CA. The Jet Propulsion Laboratory's Mars Surveyor Operations Project
operates the Mars Global Surveyor spacecraft with its industrial
partner, Lockheed Martin Astronautics, from facilities in Pasadena, CA
and Denver, CO.
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