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The top image is a MASCS VIRS interpolated color composite of craters Eminescu (center), with Xiao Zhao and Eastman toward the east and in Mercury's mid-latitudes. The bottom image is a monochrome MDIS mosaic of the same area. Yellow areas correspond to high values in both the red and green channels, that is, high reflectance (at 575 nm) and high values of the 415-nm/575-nm reflectance ratio. In some cases these spectral characteristics are associated with fresh material (like the rays of Xiao Zhao) that has been less affected by space weathering. Hollows, such as those found on and around the central peak of Eminescu, have similar colors.
The VIRS composite shows hundreds of individual footprints tracks (minimum 100-200 m across and 3-4 km long) taken from different directions and altitudes. In locations where multiple footprints cover the same area, the footprint with the best illumination for mineralogical interpretation (usually the lowest incidence angle where shadows are minimized) is used for making the map. In areas where footprints are sparse (separated by tens of km), observations are interpolated for complete coverage of the surface. In the MDIS mosaic, some brightness variations are due to tiling of images taken at different illuminations.
Date Created: June 16, 2014
Instruments: Visible and Infrared Spectrograph (VIRS) of the Mercury Atmosphere and Surface Composition Spectrometer (MASCS) and Mercury Dual Imaging System (MDIS)
VIRS Color Composite Wavelengths: 575 nm as red, 415 nm/750 nm as green, 310 nm/390 nm as blue
Center Latitude: 10.0°
Center Longitude: 114.3° E
Resolution: 1 km/pixel
Scale: Eminescu crater(center) is about 130 km (80 mi.) in diameter
Image credit: NASA/Johns Hopkins University Applied Physics Laboratory/Carnegie Institution of Washington
As anticipated in Monday's posting, MESSENGER has started to send back its two-month backlog of images. Included in the recently arrived batch is this triple take of Xiao Zhao. This image is very similar to this image from June 2012 and this image from December 2012; Xiao Zhao is one of the locations being repeatedly imaged to look for any slight hints of change.
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: December 04, 2013
Image Mission Elapsed Time (MET): 28472584
Image ID: 5318200
Instrument: Narrow Angle Camera (NAC) of the Mercury Dual Imaging System (MDIS)
Center Latitude: 10.65°
Center Longitude: 123.94° E
Resolution: 34 meters/pixel
Scale: Xiao Zhao is 24 km (15 miles) in diameter
Incidence Angle: 24.9°
Emission Angle: 32.4°
Phase Angle: 44.7°
Photo credit: NASA/Johns Hopkins University Applied Physics Laboratory/Carnegie Institution of Washington
Centered in this stunning image lies Eminescu crater, illuminated by a bright halo of material around its edge. The ends of a ray system emanating from Xiao Zhao are on the right side of the image. Standing in stark contrast with the low reflectance material within the crater (identifiable as the dark regions on the crater's floor) are bright hollows (identifiable as the bright ring near the crater's center).
Today's image title is in reference to the Cat's Eye Nebula, a well studied, iconic nebula that shares similar features to this image of Eminescu, such as notably the blues, yellows, and spherical shape of the formation.
Date acquired: January 03, 2012
Image Mission Elapsed Time (MET): 234069356, 234069376, 234069360
Image ID: 1218103, 1218108, 1218104
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: 10.47°
Center Longitude: 113.8° E
Resolution: 466 meters/pixel
Scale: Eminescu has a diameter 130 km (81 mi)
Incidence Angle: 26.6°
Emission Angle: 23.5°
Phase Angle: 50.2°
Photo credit: NASA/Johns Hopkins University Applied Physics Laboratory/Carnegie Institution of Washington
The crater shown here is Xiao Zhao, a relatively young crater with a prominent system of bright rays. This image is extremely similar to one acquired previously, and that is by design. Certain features, like Xiao Zhao and locations with hollows, are being repeatedly imaged to look for any slight hints of change.
Date acquired: December 19, 2012
Image Mission Elapsed Time (MET): 264389643
Image ID: 3167776
Instrument: Narrow Angle Camera (NAC) of the Mercury Dual Imaging System (MDIS)
Center Latitude: 10.64°
Center Longitude: 123.9° E
Resolution: 58 meters/pixel
Scale: Xiao Zhao has a diameter of 24 kilometers (15 miles).
Incidence Angle: 20.3°
Emission Angle: 40.8°
Phase Angle: 58.5°
Photo credit: NASA/Johns Hopkins University Applied Physics Laboratory/Carnegie Institution of Washington
The bright rays of Xiao Zhao dominate this scene. These rays indicate that Xiao Zhao is a relatively young crater. Eastman crater can be seen to the southwest of Xiao Zhao. The eight different color filters of the WAC that are used to create the color base map have central wavelengths of 430, 480, 560, 630, 750, 830, 900, and 1000 nm. The images acquired through these narrow-band filters are combined to create color images that accentuate color differences on Mercury's surface. As an example, this image was created by using three images acquired as part of the color base map with the central wavelengths of 1000, 750, and 430 nm displayed in red, green, and blue, respectively. This particular combination allows the visualization of details, some of which would be invisible to the human eye.
Date acquired: December 29, 2011
Image Mission Elapsed Time (MET): 233687507, 233687511, 233687527
Image ID: 1199649, 1199650, 1199654
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: 9.6°
Center Longitude: 125.8° E
Resolution: 443 meters/pixel
Scale: The rayed crater Xiao Zhao is 24 km (15 mi.) in diameter.
Incidence Angle: 26.9°
Emission Angle: 14.1°
Phase Angle: 28.0°
Photo credit: NASA/Johns Hopkins University Applied Physics Laboratory/Carnegie Institution of Washington
Xiao Zhao, a relatively small fresh crater, stretches its rays across this entire image, illustrating that small impacts are still quite powerful. The bright crater rays, composed of fresh material excavated by the impact, are contrasted by the older, darker surrounding surface. Another small impact crater well known for its extensive rays is Han Kan.
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 250-meter/pixel (820 feet/pixel) morphology base map or the 1-kilometer/pixel (0.6 miles/pixel) color base map. It is not possible to cover all of Mercury's surface at this high resolution during MESSENGER's one-year mission, but several areas of high scientific interest are generally imaged in this mode each week.
Date acquired: July 11, 2011
Image Mission Elapsed Time (MET): 218840609
Image ID: 489105
Instrument: Wide Angle Camera (WAC) of the Mercury Dual Imaging System (MDIS)
WAC filter: 9 (996 nanometers)
Center Latitude: 14.17°
Center Longitude: 122.3° E
Resolution: 456 meters/pixel
Scale: Diameter of Xiao Zhao is 24.2 kilometers (15.0 miles)
Incidence Angle: 22.1°
Emission Angle: 34.3°
Phase Angle: 56.4°
Photo credit: NASA/Johns Hopkins University Applied Physics Laboratory/Carnegie Institution of Washington
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