Secondary Impact Craters on a Lobate Scarp

In and of itself, this image of a portion of a north-south-trending lobate scarp, situated midway between Firdousi crater and Caravaggio basin, is not particularly noteworthy. Look a little closer, however, and this little part of Mercury's surface takes on a strange, pitted appearance. A number of shallow, teardrop-shaped depressions occur throughout the image, aligned from the top-left to the bottom-right. This distinctive surface texture is likely caused by debris thrown out by nearby impacts (there is a crater 11 km, or 7 miles, in diameter to the southeast that might be responsible, for example). If so, then these small depressions are effectively secondary impact craters-but not quite like those we're used to seeing. The difference between these depressions and what we normally think of as secondary craters is likely due to size: as MESSENGER gets closer to the surface of Mercury, we are seeing more and more fascinating features at ever greater resolutions. What else will we see before MESSENGER's adventure ends?

This image was acquired as a high-resolution targeted observation. Targeted observations are images of a small area on Mercury's surface at resolutions much higher than the 200-meter/pixel morphology base map. It is not possible to cover all of Mercury's surface at this high resolution, but typically several areas of high scientific interest are imaged in this mode each week.

Date acquired: July 31, 2014
Image Mission Elapsed Time (MET): 49172453
Image ID: 6788651
Instrument: Narrow Angle Camera (NAC) of the Mercury Dual Imaging System (MDIS)
Center Latitude: 1.2°
Center Longitude: 77.7° E
Resolution: 23 meters/pixel
Scale: The left-to-right field of view in this image is 21 km (13 miles) across
Incidence Angle: 77.1°
Emission Angle: 1.9°
Phase Angle: 78.9°
Orientation: North is up in this image.

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

Firdousi Crater

Firdousi is a relatively fresh impact crater approximately 96 kilometers (60 miles) in diameter. Its abundant secondary craters dominate the surroundings, and many have haloes of high-reflectance, relatively blue ejecta.

Date acquired: August 14, 2011
Image Mission Elapsed Time (MET): 221844487, 221844483, 221844479
Image ID: 632390, 632389, 632388
Instrument: Wide Angle Camera (WAC) of the Mercury Dual Imaging System (MDIS)
WAC filters: 9, 7, 6 (996, 748, 433 nanometers) in red, green, and blue
Center Latitude: 4.19°
Center Longitude: 65.30° E
Resolution: 204 meters/pixel
Scale: Firdousi is approximately 96 kilometers (60 miles) in diameter
Incidence Angle: 37.0°
Emission Angle: 14.6°
Phase Angle: 51.7°

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

Firdousi Crater and Region

This image shows a portion of Mercury's surface mainly consisting of smooth plains material. This lighter, smoother area of plains is younger than the darker, rougher surrounding terrain near the edges of this image. Firdousi crater and its halo of small secondary craters is also apparent in this image, in the lower left quadrant.

Date acquired: July 17, 2011
Image Mission Elapsed Time (MET): 219349510, 219349512, 219349518
Image ID: 513659, 513658, 513662
Instrument: Wide Angle Camera (WAC) of the Mercury Dual Imaging System (MDIS)
WAC filter: 9 (1000 nanometers), 7 (750 nanometers), 6 (433 nanometers) as red-green-blue
Center Latitude: 6.77°
Center Longitude: 69.01° E
Resolution: 1330 meters/pixel
Scale: The large crater in the lower left quadrant of this image is about 134 kilometers (80 miles) in diameter
Incidence Angle: 52.4°
Emission Angle: 0.3°
Phase Angle: 52.4°

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