Dark Rays on Mercury Target Name:   Mercury Spacecraft:   MESSENGER Produced by:   NASA/JHUAPL Copyright:  Copyright Free Date Released:  October 14, 2008

• Mercury
• MESSENGER

Date Acquired: October 6, 2008
Image Mission Elapsed Time (MET): 131773885
Instrument: Narrow Angle Camera (NAC) of the Mercury Dual Imaging System (MDIS)
Resolution: 520 meters/pixel (0.32 miles/pixel)
Scale: The top of this image is about 530 kilometers across (330 miles)
Spacecraft Altitude: 20,000 kilometers (12,000 miles)

When a meteoroid strikes the surface of a planet, material from the surface is ejected outward at high velocity, often creating rays that extend over distances far greater than the size of the crater formed by the impact. During MESSENGER's second Mercury flyby, MDIS captured images of impressive rays on Mercury, such as the ejecta prominent around Kuiper crater and the extensive ray system associated with a newly imaged crater in Mercury's northern latitudes. In both of those examples, the rays appear bright, which is characteristic of freshly pulverized rock and indicates that the rays are younger than much of Mercury's surface. In contrast, in the upper portion of this NAC image, a set of dark rays is seen emerging from a small crater. Dark rays are rare on Mercury, but other occurrences have been identified, such as at Mozart crater (imaged during MESSENGER's first Mercury flyby). Mozart crater is interpreted to have excavated dark material from depth during the impact event, creating dark streamers. The dark rays from the crater shown here may have a similar origin, and color imaging from the Wide Angle Camera (WAC) gathered during the flyby is being used to explore the nature of these unusual dark rays further.

Credit: NASA/Johns Hopkins University Applied Physics Laboratory/Carnegie Institution of Washington