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This NAC image displays a number of interesting geologic features
characteristic of Mercury’s surface. The crater indicated by the yellow
arrow has unusual bright material on its floor, likely due to rocks of a
different chemical composition. Bright material also has been seen in
the craters Sander and Kertész. The pink arrows point to a pair of larger
and older craters that have been flooded with now solidified volcanic
lava, similar to flooding seen at the impact basin Raphael. In the lower
right-hand corner of the image is a large peak-ring basin, about 210
kilometers (130 miles) in diameter, which also appears to have been
flooded with lava. There is a small scarp (cliff) within that basin that
cuts through a smaller crater at the edge of the basin's inner ring, at
the point indicated by the blue arrow. Scarps on Mercury are often seen
intersecting impact craters, such as this dramatic, previously released
image from the mission's second Mercury flyby (see PIA11358). The green
arrows on the left side of the image indicate a series of secondary crater
chains. Chains of small craters such as these are formed when ejecta are
expelled from a primary crater after the initial impact. Secondaries are
widespread across Mercury's surface, as was also discussed in the caption
to this previously released image (see PIA10178). Unraveling Mercury's
geologic history requires investigating the complex and overlapping
relationships of volcanic plains, impacts, and scarps seen on the planet's
surface.
Date Acquired: October 6, 2008
Image Mission Elapsed Time (MET): 131774026
Instrument: Narrow Angle Camera (NAC) of the Mercury Dual Imaging System (MDIS)
Resolution: 540 meters/pixel (0.33 miles/pixel)
Scale: This image is about 550 kilometers (340 miles) across
Spacecraft Altitude: 21,000 kilometers (13,000 miles)
These images are from MESSENGER, a NASA Discovery mission to conduct the
first orbital study of the innermost planet, Mercury. For information
regarding the use of images, see the MESSENGER image use policy.