Signs of Aging... (natural colors; credits: Lunexit)

Date Acquired: October 6, 2008
Image Mission Elapsed Time (MET): 131766454
Instrument: Narrow Angle Camera (NAC) of the Mercury Dual Imaging System (MDIS)
Resolution: 420 meters/pixel (0,26 miles/pixel) on the right side of the image
Scale: The small crater superimposed on the long cliff is about 30 Km (approx. 19 miles) in diameter
Spacecraft Altitude: about 16.500 kilometers (approx. 10.300 miles)

Of Interest: This dramatic NAC image was acquired about 56 minutes prior to MESSENGER’s closest approach during the mission’s recent Mercury flyby, as the spacecraft approached the Planet's illuminated crescent. Prominent toward the horizon in this view of newly imaged terrain is a long cliff face. A small impact crater (about 30 Km, or approx. 19 miles, in diameter) overlies this lengthy scarp. The scarp extends for over 400 Km (about 250 miles) and likely represents a sign of aging unique to Mercury among the planets in the Solar System.
As time passes, the interior of a planet cools. However, the relative size of Mercury's central metallic core is larger than that of the other planets and hence has significantly affected the planet’s geologic evolution. The numerous long scarps on Mercury are believed to be the surface expression of faults formed in the rocks of Mercury's crust as the interior of the planet cooled and contracted. This contraction compressed the surface and thrust some sections of crust over others, creating long curving cliffs like the one shown here.