Mercurial Limb, One Week Later

What a difference a week makes. Today's featured image was acquired earlier this month, one week after this image (PIA17579), showing how the lighting conditions change in an Earth week (but only about 4% of a Mercury day). Can you spot the crater with the prominent secondary chains? With the Sun now a bit higher above this crater (located about a quarter of the way up from the bottom of the frame), its floor appears smooth, and its crater chains can still be seen to stretch far from its rim.

This image was acquired as part of MDIS's limb imaging campaign. Once per week, MDIS captures images of Mercury's limb, with an emphasis on imaging the southern hemisphere limb. These limb images provide information about Mercury's shape and complement measurements of topography made by the Mercury Laser Altimeter (MLA) of Mercury's northern hemisphere.

Date acquired: October 09, 2013
Image Mission Elapsed Time (MET): 23629938
Image ID: 4974132
Instrument: Wide Angle Camera (WAC) of the Mercury Dual Imaging System (MDIS)
WAC filter: 7 (748 nanometers)
Center Latitude: -43.49°
Center Longitude: 150.4° E
Resolution: 1085 meters/pixel
Incidence Angle: 77.7°
Emission Angle: 57.7°
Phase Angle: 132.9°

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

Mercurial Limb

Another day, another beautiful view of Mercury's horizon. In this scene, which was acquired looking from the shadows toward the sunlit side of the planet, a 120-km (75 mile) impact crater stands out near the center. Emanating from this unnamed crater are striking chains of secondary craters, which gouged linear tracks radially away from the crater. While this crater is not especially fresh (its rays have faded into the background), it does appear to have more prominent secondary crater chains than many of its peers.

This image was acquired as part of MDIS's limb imaging campaign. Once per week, MDIS captures images of Mercury's limb, with an emphasis on imaging the southern hemisphere limb. These limb images provide information about Mercury's shape and complement measurements of topography made by the Mercury Laser Altimeter (MLA) of Mercury's northern hemisphere.

Date acquired: October 02, 2013
Image Mission Elapsed Time (MET): 23055902
Image ID: 4933174
Instrument: Wide Angle Camera (WAC) of the Mercury Dual Imaging System (MDIS)
WAC filter: 7 (748 nanometers)
Center Latitude: -52.13°
Center Longitude: 167.5° E
Resolution: 667 meters/pixel
Incidence Angle: 82.0°
Emission Angle: 69.4°
Phase Angle: 122.4°

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

Southwestern Rim of Caloris Basin

This image shows an area of the southwestern rim of the Caloris impact basin. The small hills in the lower left are part of the rim units, and the smooth surface to the right is part of the smooth plains within the basin. The scene lies right on a color boundary between darker rim material and higher-reflectance plains. Small hollows are found on the top of the hills, and small lobate scarps cross the area. The famous kidney-shaped pyroclastic vent is just to the east (right), out of the scene.

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 03, 2013
Image Mission Elapsed Time (MET): 15137794
Image ID: 4370103
Instrument: Narrow Angle Camera (NAC) of the Mercury Dual Imaging System (MDIS)
Center Latitude: 22.04°
Center Longitude: 143.6° E
Resolution: 42 meters/pixel
Scale: The scene is about 57 km (35 mi.) across
Incidence Angle: 68.7°
Emission Angle: 31.8°
Phase Angle: 100.1°
North is up in this image.

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

Earth

Launched on August 3, 2004, the MESSENGER spacecraft's trajectory took it back to Earth for a gravity assist flyby a year later. This image, taken on August 2, 2005 as MESSENGER prepared to depart again for the inner Solar System, shows the western margin of the South American continent (bottom), Mexico (top), and the tropical depression that would develop into Tropical Storm Harvey the next day (far right).

Today's image of Earth serves two purposes. First, it recalls the remarkable journey MESSENGER has undertaken since launch to become the first spacecraft to orbit Mercury. But it also reinforces the concept of comparative planetology that much of what we know of Mercury's geology is rooted in what we have learned from studying our home planet. Whether it be Mercury's large-scale tectonic deformation, its widespread volcanic resurfacing, or even how impacts have shaped its surface, Earth has given scientists a thorough grounding in the tools needed to understand the innermost planet.

Date acquired: August 2, 2005
Image Mission Elapsed Time (MET): 31489858
Image ID: 1063
Instrument: Wide Angle Camera (WAC) of the Mercury Dual Imaging System (MDIS)
Center Latitude: -0.4°
Center Longitude: 269.8° E
Resolution: 7.6 kilometers/pixel
Scale: The field of view in this image covers approx. 64° of arc (7,137 km or 4,436 mi.) across Earth's surface
Incidence Angle: 22.5°
Emission Angle: 33.6°
Phase Angle: 55.5°
The north pole is to the top right in this image.

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

Contrast Stretch of Matisse Crater

Today's feature is the 748-nm filter image from from the October 21, 2013 color presentation. The graphs underneath the image illustrate a basic principle of image processing: the contrast stretch. A computer is typically capable of displaying a black and white ("greyscale") image as a series of pixels with 256 levels of brightness, between 0 (black) and 255 (white). Therefore, in order to be displayed, the numerical values of the image must be "stretched" to cover the range 0 to 255. In the case of a calibrated MDIS image, the image values are in physical units of reflectance -- that is, the percentage of incident light that the surface reflects. The graphs underneath the image are histograms. The x-axis is the range of pixel values that occur in the image, and the y-axis is the frequency of the values. The histogram on the lower left shows that the range of reflectance values in the image is from about 0.02 to 0.07 (or about 2% to 7% reflectance). The plot peaks at about 0.04, indicating that the most frequent pixel value is about 0.04. The plot on the lower right shows how the input pixel values have been scaled from 0 to 255 to produce the image above. Note that to display a color image (i.e., in red-green-blue), each of the three input color planes is stretched separately.

This image was acquired as a high-resolution targeted color observation. Targeted color observations are images of a small area on Mercury's surface at resolutions higher than the 1-kilometer/pixel 8-color base map. During MESSENGER's one-year primary mission, hundreds of targeted color observations were obtained. During MESSENGER's extended mission, high-resolution targeted color observations are more rare, as the 3-color base map covered Mercury's northern hemisphere with the highest-resolution color images that are possible.

Date acquired: October 21, 2012
Image Mission Elapsed Time (MET): 259266840
Image ID: 2803280
Instrument: Wide Angle Camera (WAC) of the Mercury Dual Imaging System (MDIS)
WAC filter: 7 (748 nanometers)
Center Latitude: -23.00°
Center Longitude: 268.4° E
Resolution: 674 meters/pixel
Scale: The scene is about 890 km (553 mi.) across
Incidence Angle: 45.6°
Emission Angle: 33.5°
Phase Angle: 78.7°
North is up in this image.

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

Double Impact Crater and Digital Elevation Model

The unnamed crater featured in this image might look like a ringed basin at high sun angles, but as can be clearly seen from the inset perspective view, in which the height is exaggerated 5 times, the central portion is a second crater that impacted the middle of the older crater. Such perspective views make use of a digital elevation model (DEM), which can be constructed either by accumulating topographic profiles from the MLA instrument or from measurements of shadows in images (or "photoclinometry"). In this case, the basemap is draped over the Gaskell DEM, which is constructed using photoclinometry. You can make your own perspective views of Mercury's surface using the QuickMap tool.

This image was acquired as part of MDIS's high-resolution stereo imaging campaign. Images from the stereo imaging campaign are used in combination with the surface morphology base map or the albedo base map to create high-resolution stereo views of Mercury's surface, with an average resolution of 200 meters/pixel. Viewing the surface under the same Sun illumination conditions but from two or more viewing angles enables information about the small-scale topography of Mercury's surface to be obtained.

Date acquired: January 14, 2012
Image Mission Elapsed Time (MET): 234999326
Image ID: 1263152
Instrument: Narrow Angle Camera (NAC) of the Mercury Dual Imaging System (MDIS)
Center Latitude: -42.23°
Center Longitude: 40.26° E
Resolution: 188 meters/pixel
Scale: The unnamed crater is ~83 km (52 mi.) across
Incidence Angle: 70.8°
Emission Angle: 22.9°
Phase Angle: 76.1°

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

Catullus Crater

Named for the Roman poet Gaius Valerius Catullus, this impact crater, 100 km (62 mi.) in diameter, has a smoothly textured floor like that seen elsewhere on Mercury. The western portion of the floor (right) abuts against the inner, terraced wall of the crater (middle), which is bordered by the surrounding, older terrain (left). Scientists know of two ways to render the floor of a crater smooth: impact melt or volcanism. It can be difficult to differentiate the two processes, however, and so the nature of the smooth material within Catullus remains unknown. However, in a larger view a depression can be seen in the center of Catullus that may be volcanic in nature -- and so too might the floor of the crater itself.

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: August 8, 2013
Image Mission Elapsed Time (MET): 18306428
Image ID: 4595268
Instrument: Narrow Angle Camera (NAC) of the Mercury Dual Imaging System (MDIS)
Center Latitude: 21.98°
Center Longitude: 293.43° E
Resolution: 39 meters/pixel
Scale: The field of view in this image is approx. 40 km (25 mi.) across
Incidence Angle: 68.1°
Emission Angle: 3.5°
Phase Angle: 71.6°
North is down in this image.

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

Pyroclastic Deposits at Matisse Crater

This color view of the vicinity of Matisse crater, seen in an early Gallery image from MESSENGER's first flyby of Mercury in 2008. Two unnamed craters formed tangentially to the rim of Matisse (one just inside the rim, and one just outside). These craters have bright orange deposits on their floors. High reflectance and a greater-than-average ("red") spectral slope create the orange appearance in this color presentation. Such color characteristics are found at many other locations on Mercury where pyroclastic volcanic eruptions took place.

This image was acquired as a high-resolution targeted color observation. Targeted color observations are images of a small area on Mercury's surface at resolutions higher than the 1-kilometer/pixel 8-color base map. During MESSENGER's one-year primary mission, hundreds of targeted color observations were obtained. During MESSENGER's extended mission, high-resolution targeted color observations are more rare, as the 3-color base map covered Mercury's northern hemisphere with the highest-resolution color images that are possible.

Date acquired: October 21, 2012
Image Mission Elapsed Time (MET): 259266820, 259266840, 259266824
Image ID: 2803275, 2803280, 2803276
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: -23.00°
Center Longitude: 268.4° E
Resolution: 674 meters/pixel
Scale: The scene is about 890 km (553 mi.) across; Matisse crater is about 186 km (116 mi.) in diameter
Incidence Angle: 45.6°
Emission Angle: 33.5°
Phase Angle: 78.7°
North is up in this image.

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

Steichen Impact Basin

The large, older crater featured in today's image is Steichen. At almost 200 km (124 mi.) across, Streichen is a complex impact basin, with a central peak ring that is partially buried by smooth crater floor deposits. Though much of the northwestern central peak ring is buried, one tiny, bright blue speck surrounded by a dark blue halo pokes up through the smooth floor deposits, hinting that hollows might be forming in a little patch of excavated low-reflectance material.

This image was acquired as part of MDIS's 8-color base map. The 8-color base map is composed of WAC images taken through eight different narrow-band color filters and covers more than 99% of Mercury's surface with an average resolution of 1 kilometer/pixel. The highest-quality color images are obtained for Mercury's surface when both the spacecraft and the Sun are overhead, so these images typically are taken with viewing conditions of low incidence and emission angles.

Date acquired: August 13, 2011
Image Mission Elapsed Time (MET): 221758501, 221758509, 221758503
Image ID: 628307, 628312, 628308
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: -12.53°
Center Longitude: 78.18° E
Resolution: 623 meters/pixel
Scale: Steichen crater is 196 km (122 mi.) in diameter.
Incidence Angle: 48.3°
Emission Angle: 0.2°
Phase Angle: 48.2°

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

Lobate Scarp Cutting Through Unnamed Crater

Today's image features an unnamed crater 35 km (~22 mi.) in diameter that is cross-cut by a lobate scarp. Superposition relations such as these provide scientists with strong evidence that the surface of Mercury has been extensively shortened, likely in response to the cooling and contraction of the planet's interior through time. Additionally, the change in shape of a once-circular crater cut by a scarp provides a way to estimate the amount of horizontal shortening across that scarp. Such relations, therefore, offer an import insight into the broader geological development of Mercury!

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: August 13, 2013
Image Mission Elapsed Time (MET): 18677753
Image ID: 4621861
Instrument: Narrow Angle Camera (NAC) of the Mercury Dual Imaging System (MDIS)
Center Latitude: -7.05°
Center Longitude: 70.65° E
Resolution: 63 meters/pixel
Scale: The field of view in this image is approx. 80 km (50 mi.) across
Incidence Angle: 70.4°
Emission Angle: 32.8°
Phase Angle: 103.2°
North is up in this image.

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

Tansen Crater

First seen by Mariner 10 in 1974, Tansen has not been featured on MESSENGER's gallery until today. It is among Mercury's smaller named craters at just 27 kilometers (~17 mi.) in diameter. The ejecta rays formed by the impact appear prominent in this color mosaic, as does the small, fresh crater ejecta deposit at the very top of the image.

This image was acquired as a targeted high-resolution 11-color image set. Acquiring 11-color targets is a new campaign that began in March 2013 and that utilizes all of the WAC's 11 narrow-band color filters. Because of the large data volume involved, only features of special scientific interest are targeted for imaging in all 11 colors.

Date acquired: September 09, 2013
Image Mission Elapsed Time (MET): 21069217, 21069209, 21069205
Image ID: 4791897, 4791895, 4791894
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: 3.84°
Center Longitude: 288.4° E
Resolution: 301 meters/pixel
Scale: Tansen is approximately 27 kilometers (17 mi.) in diameter
Incidence Angle: 31.7°
Emission Angle: 24.5°
Phase Angle: 56.2°

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

Kosho Crater

Today's image introduces crater Kosho, which sits in Mercury's northern hemisphere. Kosho, 65 km (~40 mi.) in diameter, is a complex crater. The long shadows in this image accentuate Kosho's central peak, which is approximately 2 km (~1.2 mi.) high. Kosho crater is named for a thirteenth century Japanese sculptor famous for his depictions of Buddhist Monks.

This image was acquired as part of MDIS's minimum-phase-angle color campaign. Near the north polar region, the incidence angle (measured from the vertical) is always fairly high because the Sun is low on the horizon. The minimum-phase-angle color campaign acquires images under conditions that minimize the shadows in an image by viewing the surface as nearly as possible from the same direction as the Sun's illumination, which minimizes the phase angle. Images are acquired through five of the WAC's narrow-band color filters, for regions north of 60° N, at an average resolution of 500 meters/pixel. The minimum-phase-angle color campaign began in March 2013.

Date acquired: September 17, 2013
Image Mission Elapsed Time (MET): 21703926
Image ID: 4836915
Instrument: Wide Angle Camera (WAC) of the Mercury Dual Imaging System (MDIS)
WAC filter: 7 (748 nanometers)
Center Latitude: 60.01°
Center Longitude: 220.2° E
Resolution: 269 meters/pixel
Scale: Kosho crater is approximately 65 km (40 mi.) in diameter
Incidence Angle: 83.3°
Emission Angle: 55.3°
Phase Angle: 28.0°

Photo credit:

Degas Crater

This close up of Degas crater shows off its grand central peaks, which are made up of sub-surface material uplifted by the impact. Over time, material from the tops of the central peaks has slid downslope, exposing fresh material that appears bright in this image. The long cracks appearing around the central peaks were likely formed as the impact melt in the bottom of the crater cooled.

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: September 17, 2013
Image Mission Elapsed Time (MET): 21761231
Image ID: 4841024
Instrument: Narrow Angle Camera (NAC) of the Mercury Dual Imaging System (MDIS)
Center Latitude: 36.99°
Center Longitude: 232.8° E
Resolution: 18 meters/pixel
Scale: Degas is 55 km (approximately 34 mi.) in diameter.
Incidence Angle: 67.9°
Emission Angle: 1.6°
Phase Angle: 66.2°
Orientation: North is towards the bottom of the image.

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

Neruda Crater

Today's image features Neruda crater, named for the Chilean poet Pablo Neruda. The crater exhibits several central peaks punctuated by a more recent, small crater, resulting in a rugged profile of ups and downs if one were to traverse the crater floor. Similarly, the crater's namesake Neruda experienced a number of ups and downs in his life, from success as a poet, through poverty, war and ultimately alleged poisoning.

Date acquired: July 24, 2012
Image Mission Elapsed Time (MET): 251577944
Image ID: 2256593
Instrument: Narrow Angle Camera (NAC) of the Mercury Dual Imaging System (MDIS)
Center Latitude: -52.20°
Center Longitude: 125.3° E
Resolution: 142 meters/pixel
Scale: Neruda crater is 112 km (69 mi) in diameter
Incidence Angle: 80.4°
Emission Angle: 2.4°
Phase Angle: 78.0°

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