This scene was imaged by MESSENGER's Narrow Angle Camera (NAC) on the
Mercury Dual Imaging System (MDIS) during the spacecraft's flyby of
Mercury on January 14, 2008. The scene is part of a mosaic that covers a
portion of the hemisphere not viewed by Mariner 10 during any of its three
flybys (1974-1975). The surface of Mercury is revealed at a resolution of
about 250 meters/pixel (about 820 feet/pixel). For this image, the Sun is
illuminating the scene from the top and north is to the left.
The outer diameter of the large double ring crater at the center of the
scene is about 260 km (about 160 miles). The crater appears to be filled
with smooth plains material that may be volcanic in nature. Multiple
chains of smaller secondary craters are also seen extending radially
outward from the double ring crater. Double or multiple rings form in
craters with very large diameters, often referred to as impact basins. On
Mercury, double ring basins begin to form when the crater diameter exceeds
about 200 km (about 125 miles); at such an onset diameter the inner rings
are typically low, partial, or discontinuous. The transition diameter at
which craters begin to form rings is not the same on all bodies and,
although it depends primarily on the surface gravity of the planet or
moon, the transition diameter can also reveal important information about
the physical characteristics of surface materials. Studying impact
craters, such as this one, in the more than 1200 images returned from this
flyby will provide clues to the physical properties of Mercury's surface
and its geological history.
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.
