Giant scarps (cliffs), called rupes (see PIA10609), are believed to have
formed when Mercury’s interior cooled and the entire planet shrank
slightly as a result. This figure, recently published in Science
magazine, shows one of these scarps (white arrows) that is about 270
kilometers (170 miles) long. This portion of Mercury’s surface was seen
during the Mariner 10 flybys, but this scarp, despite its large size, was
not visible in the Mariner 10 photos because the Sun was nearly overhead
at the time and, consequently, the scarp did not cast a discernable
shadow. In contrast, MESSENGER acquired a mosaic of this area (see PIA10605)
before the spacecraft’s closest approach to the planet, when this portion
of the surface was near the terminator, the line between the sunlit
dayside and the dark night side of the planet. Such lighting produced
long shadows, enabling this rupes to be recognized for the first time.
Date Acquired: January 14, 2008
Image Mission Elapsed Time (MET): Mosaic of images from 108821370, 108821375, 108821397, and 108821402
Instrument: A: Narrow Angle Camera (NAC) of the Mercury Dual
Imaging System (MDIS)
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.
