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Scientists have known since Mariner 10 that Mercury has contracted. This contraction is a result of the cooling of Mercury's interior, and is the process responsible for the formation of the planet's wrinkle ridges and lobate scarps. For almost four decades, however, the amount of global contraction measured from spacecraft data has been substantially less than that predicted by models of the thermal evolution of Mercury.
Now, using global photogeological and topographic MESSENGER data of Mercury, members of the MESSENGER team have mapped almost 6,000 ridges and scarps across the planet. Today's image shows the result of this mapping work, with structures color-coded according to one of four classes. (The global photogeological and topographic data used in this study are shown in the bottom left and right, respectively, of the image.) With these results, the MESSENGER team has calculated that Mercury contracted to a much greater extent than had been determined previously from mapping -- by up to seven times more, in fact.
This study was published online in the journal Nature Geoscience on Sunday, March 16, 2014, and is being presented today in the "Mercury" session at the 45th Lunar and Planetary Science Conference, which is being held this week in The Woodlands, Texas. In total, MESSENGER team members are presenting 25 papers at this conference.
Date published online: March 16, 2014
Center Latitude: 0°
Center Longitude: 0°E
Projection: Molleweide
Reference: Byrne et al. (2014) Mercury's global contraction much greater than earlier estimates, Nature Geoscience, doi:10.1038/NGEO2097
Map credit: NASA/Johns Hopkins University Applied Physics Laboratory/Carnegie Institution of Washington
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
The bright, rayed crater in this image is one of the most prominent on Mercury. Named Snorri, after an Icelandic writer and poet, the crater was discovered in images returned by the Mariner 10 spacecraft. A color view of Snorri and surroundings was presented in a previous Gallery image (PIA14233).
Date acquired: October 14, 2011
Image Mission Elapsed Time (MET): 227045180
Image ID: 882221
Instrument: Narrow Angle Camera (NAC) of the Mercury Dual Imaging System (MDIS)
Center Latitude: -9.42°
Center Longitude: 277.1° E
Resolution: 195 meters/pixel
Scale: Snorri is about 21 km (13 mi.) in diameter.
Incidence Angle: 22.4°
Emission Angle: 51.0°
Phase Angle: 73.4°
Photo credit: NASA/Johns Hopkins University Applied Physics Laboratory/Carnegie Institution of Washington
This oblique view highlights, from top to bottom, Balzac, Phidias, Tyagaraja, Stevenson, and Zeami craters. While named craters are still sparse across much of Mercury, this region was observed by Mariner 10, allowing for plenty of time to propose names. In Mariner 10 images of Mercury, craters like Tyagaraja and Zeami were described as hosting bright floor deposits, but the relatively low resolution at which they were imaged did not allow for a more detailed analysis. We now know that craters such as these host hollows (see the links above for higher resolution images of each crater in this scene).
Date acquired: November 26, 2012
Image Mission Elapsed Time (MET): 262401199, 262401219, 262401203
Image ID: 3026482, 3026487, 3026483
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: 4.64°
Center Longitude: 210.5° E
Resolution: 698 meters/pixel
Scale: Tyagaraja crater (center) is approximately 97 km (60 mi.) in north-south diameter
Incidence Angle: 30.2°
Emission Angle: 57.5°
Phase Angle: 83.8°
North is up in this image.
Photo credit: NASA/Johns Hopkins University Applied Physics Laboratory/Carnegie Institution of Washington
This image shows the crater Theophanes, which was originally imaged by Mariner 10. It is named after the Byzantine iconographer known as Theophanes the Greek. Though he was born in Constantinople, the capitol of the Byzantine Empire, around 1340 CE, Theophanes spent most of his life in Russia, where he moved in 1370 CE. It was in Russia that he gained notoriety as an icon painter. Some of his more prominent works include Our Lady of the Don and the Transfiguration of Christ. He is also known as the teacher and mentor of the great medieval Russian painter Andrei Rublev, the eponym of Rublev crater.
Date acquired: October 03, 2012
Image Mission Elapsed Time (MET): 257735204
Image ID: 2694715
Instrument: Narrow Angle Camera (NAC) of the Mercury Dual Imaging System (MDIS)
Center Latitude: -5.04°
Center Longitude: 217.2° E
Resolution: 74 meters/pixel
Scale: The crater Theophanes has diameter of ~46 km ( 29 mi.).
Incidence Angle: 69.3°
Emission Angle: 2.2°
Phase Angle: 71.6°
Photo credit: NASA/Johns Hopkins University Applied Physics Laboratory/Carnegie Institution of Washington
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