Xiao Zhao Crater

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

Impact Craters in Rasditladi Quadrant

If absence makes the heart grow fonder, then many on the MESSENGER team are now really fond of MDIS images! It has been over two months since the MESSENGER spacecraft returned images of Mercury's surface through routine downlink operations. Shown here is one of the last images sent before the two month gap. The lack of images is due to a very logical explanation: Mercury (and hence the MESSENGER spacecraft) has been on the opposite side of the Sun from the Earth, limiting the amount of data that can be downlinked. Generally, MDIS images take up more room than the data from MESSENGER's other instruments, so MDIS images are downlinked last, after all other instrument data are down. Happily, the distance between Mercury and the Earth is now decreasing; check out where both planets are today. Soon, we'll again have new images of Mercury's surface!

This image was acquired as part of MDIS's high-incidence-angle base map. The high-incidence-angle base map complements the surface morphology base map of MESSENGER's primary mission that was acquired under generally more moderate incidence angles. High incidence angles, achieved when the Sun is near the horizon, result in long shadows that accentuate the small-scale topography of geologic features. The high-incidence-angle base map was acquired with an average resolution of 200 meters/pixel.

Date acquired: November 20, 2013
Image Mission Elapsed Time (MET): 27234508
Image ID: 5230158
Instrument: Wide Angle Camera (WAC) of the Mercury Dual Imaging System (MDIS)
WAC filter: 7 (748 nanometers)
Center Latitude: 44.20°
Center Longitude: 223.3° E
Resolution: 150 meters/pixel
Scale: This image is roughly 280 km (170 miles) across
Incidence Angle: 60.6°
Emission Angle: 55.0°
Phase Angle: 30.0°

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

Note: This image is located near the center of Raditladi Quadrant; the closest named feature to this image is Nawahi Crater, which is some distance to the east.

Tolstoj Basin and Nureyev Crater

The Tolstoj basin (355 km in diameter) can be seen at the bottom edge of the frame, its center filled with smooth plains and surrounded by a large region of low-reflectance ejecta. The fresh, bright-rayed crater Nureyev is visible near the limb.

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: November 21, 2013
Image Mission Elapsed Time (MET): 27346412
Image ID: 5238318
Instrument: Wide Angle Camera (WAC) of the Mercury Dual Imaging System (MDIS)
WAC filter: 7 (748 nanometers)
Center Latitude: -4.37°
Center Longitude: 188.8° E
Resolution: 1015 meters/pixel
Incidence Angle: 14.6°
Emission Angle: 58.8°
Phase Angle: 63.2°

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

To Ngoc Van Crater

Crater To Ngoc Van, named for a Vietnamese painter, is seen at the top of this image. The oblique angle provides a great view into the irregularly shaped pit within To Ngoc Van, which is thought to have formed via explosive volcanism and provides evidence for Mercury's geologically active past. Many of the smaller (5-10 km) craters in this scene were produced as secondary impacts from the ejecta of nearby Ahmad Baba crater. North is to the left in this image.

This image was acquired as part of MDIS's high-incidence-angle base map. The high-incidence-angle base map complements the surface morphology base map of MESSENGER's primary mission that was acquired under generally more moderate incidence angles. High incidence angles, achieved when the Sun is near the horizon, result in long shadows that accentuate the small-scale topography of geologic features. The high-incidence-angle base map was acquired with an average resolution of 200 meters/pixel.

Date acquired: November 19, 2013
Image Mission Elapsed Time (MET): 27148228
Image ID: 5223996
Instrument: Wide Angle Camera (WAC) of the Mercury Dual Imaging System (MDIS)
WAC filter: 7 (748 nanometers)
Center Latitude: 53.36°
Center Longitude: 239.6° E
Resolution: 154 meters/pixel
Scale: Crater To Ngoc Van is 71 km (44 miles) in diameter
Incidence Angle: 73.7°
Emission Angle: 65.6°
Phase Angle: 30.0°

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

Double Crater

The surface of Mercury is dominated by the record of impact craters and basins that is has accrued over billions of years, and so it is no surprise that, occasionally, one impact crater forms within another. In this scene, the smaller crater in the bottom center of the image, some 16 km (10 miles) in diameter, is sited entirely within a larger crater, 40 km (25 miles) across. As we have seen often before, the Law of Superposition allows us to determine the sequence in which these craters formed -- the smaller one could not have survived the formation of the larger crater, and so formed second.

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: November 11, 2013
Image Mission Elapsed Time (MET): 26454699
Image ID: 5174833
Instrument: Narrow Angle Camera (NAC) of the Mercury Dual Imaging System (MDIS)
Center Latitude: -26.32°
Center Longitude: 248.86° E
Resolution: 80 meters/pixel
Scale: The field of view in this image is about 90 km (56 mi.) across
Incidence Angle: 70.5°
Emission Angle: 4.4°
Phase Angle: 74.9°
North is to the top of the image.

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

Terror Rupes

We have seen limb images of Mercury many times before, and they never fail to showcase the geological diversity (and splendor!) of the innermost planet. This time, something fills the scene with terror -- Terror Rupes, to be precise, the long, cliff-like landform visible at the center of the scene. Terror Rupes is one of Mercury's most prominent lobate scarps, and was named for HMS Terror, an eighteenth-century warship that later participated in scientific polar explorations. (For an explanation for how lobate scarps likely form, see this previous featured image.)

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: February 04, 2012
Image Mission Elapsed Time (MET): 236853865
Image ID: 1353252
Instrument: Wide Angle Camera (WAC) of the Mercury Dual Imaging System (MDIS)
WAC filter: 7 (748 nanometers)
Center Latitude: -69.3°
Center Longitude: 96.0° E
Resolution: 2.7 kilometers/pixel
Incidence Angle: 80.3°
Emission Angle: 50.9°
Phase Angle: 114.5°

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

Lobate Scarp in Rembrandt Basin

The Rembrandt basin is the second-largest well preserved impact structure on Mercury, and is one of the best examples of a process that has irrevocably shaped the surface of the innermost planet. Yet the planet has been fundamentally shaped by another process -- global contraction -- that has resulted in the formation of lobate scarps and wrinkle ridges across the surface of Mercury.

In this image, we see a good example of where these processes meet. The most prominent landform in the scene is a north-west-trending scarp, its eastern margin illuminated by the Sun. Scarps such as this form when one portion of Mercury's crust thrusts up over another, the result of crustal shortening in response to the planet's volume decreasing as its interior cools. Yet if you look carefully, you might spy an alignment in the texture of the surface here, trending from the bottom-left to the top-right of the image. This alignment is due to radial scouring of the surface around Rembrandt by debris thrown out during the impact that formed the basin.

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: November 5, 2013
Image Mission Elapsed Time (MET): 25999800
Image ID: 5142079
Instrument: Narrow Angle Camera (NAC) of the Mercury Dual Imaging System (MDIS)
Center Latitude: -20.99°
Center Longitude: 100.55° E
Resolution: 115 meters/pixel
Scale: The field of view in this image is about 120 km (75 mi.) across
Incidence Angle: 79.4°
Emission Angle: 12.2°
Phase Angle: 67.2°
North is to the bottom of the image.

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

Impact Crater with Pit Crater

The impact crater at the top center of this image is characterized by a sharp rim and high-reflectance ejecta. Lobes of slumped material are found where the wall meets the floor. The central peak is notable because it contains a pit. A recent survey1 found 27 central pit craters on Mercury. All of these central pit craters are located in plains units, but the mechanism by which the pits form is uncertain.

1 Z. Xiao and G. Komatsu (2013), Impact craters with ejecta flows and central pits on Mercury, Planetary and Space Science, vol. 82-83, pp. 62-78.

This image was acquired as part of MDIS's high-resolution surface morphology base map. The surface morphology base map covers more than 99% of Mercury's surface with an average resolution of 200 meters/pixel. Images acquired for the surface morphology base map typically are obtained at off-vertical Sun angles (i.e., high incidence angles) and have visible shadows so as to reveal clearly the topographic form of geologic features.

Date acquired: July 17, 2011
Image Mission Elapsed Time (MET): 219350124
Image ID: 513704
Instrument: Narrow Angle Camera (NAC) of the Mercury Dual Imaging System (MDIS)
Center Latitude: 19.42°
Center Longitude: 63.27° E
Resolution: 143 meters/pixel
Scale: The impact crater of interest is about 17 km (11 mi.) in diameter
Incidence Angle: 59.8°
Emission Angle: 12.8°
Phase Angle: 47.0°

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

Giambologna Crater

This lovely, fresh, complex crater with a crescent-shaped central peak was recently given the name Giambologna by the International Astronomical Union. The Dutch sculptor Jean Boulogne Giambologna (1529-1608) is most famous for his bronze statues of the god Mercury. The inset photograph shows one that resides in the Museo Nazionale del Bargello, Florence, Italy. Giambologna crater is distinctive for its wide, terraced western wall and the very smooth impact melt pond that covers the eastern floor. The wall terracing probably resulted from extensive collapse that happened because Giambologna formed on a slope -- the wall of an older, larger crater.

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: October 15, 2011
Image Mission Elapsed Time (MET): 227171471
Image ID: 888364
Instrument: Narrow Angle Camera (NAC) of the Mercury Dual Imaging System (MDIS)
Center Latitude: -42.86°
Center Longitude: 236.7° E
Resolution: 202 meters/pixel
Scale: Giambologna crater is about 67 km (42 mi.) in diameter; Giambologna's Mercury is 180 cm (71 in.) tall
Incidence Angle: 65.8°
Emission Angle: 23.9°
Phase Angle: 67.8°

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

Flow-Like Ejecta From an Unnamed Crater

The left side of today's image is dominated by an unnamed 75-km-diameter impact crater. The crater has several interesting features. Its western wall is quite broad, with extensive terracing and landslide scarps. The floor of the crater is flat, having been filled by volcanic plains or impact melt. The small central peaks, parts of the floor, and spots along the eastern rim are dotted with high-reflectance hollows. Finally, as outlined in the inset, the ejecta to the north and east of the rim appears to have flowed along the ground, and formed a terminal scarp. A recent paper by Beary Xiao and Goro Komatsu discusses this and other Mercurian craters that have flow-like ejecta, and makes comparisons with similar landforms on the Moon and Mars.

Z. Xiao and G. Komatsu (2013), Impact craters with ejecta flows and central pits on Mercury, Planetary and Space Science, vol. 82-83, pp. 62-78.

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: November 03, 2011
Image Mission Elapsed Time (MET): 228803487
Image ID: 966206
Instrument: Wide Angle Camera (WAC) of the Mercury Dual Imaging System (MDIS)
WAC filter: 7 (748 nanometers)
Center Latitude: 13.45°
Center Longitude: 298.0° E
Resolution: 182 meters/pixel
Scale: The scene is about 190 km (118 mi.) across
Incidence Angle: 68.6°
Emission Angle: 15.5°
Phase Angle: 55.3°
North is up in this image.

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

Messenger's 2013 Year in Review

The year 2013 has been another year of operations and discoveries for MESSENGER, finally including 100% image coverage of the planet by the Mercury Dual Imaging System (MDIS)! As another year draws to a close, we look back at some of the featured images from the year, and look forward to continued operations, including some of the highest-resolution images ever taken of Mercury, in 2014!

• January: They Call Me Muddy Waters
• February: Colors of the Innermost Planet
• March: A Colorful Group
• April: An Unnamed Wonder
• May: 100% Coverage
• June: It's a Sublimation Formation!
• July: Digital Elevation Model of Mercury's Northern Hemisphere
• August: Peek-a-boo!
• September: A Volcanic View
• October: Degas' Impression
• November: A Late Holloween
• December: On the Horizon

You can also revisit previous yearly compilations from 2008, 2009, 2010, 2011, and 2012.

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