Image and Text: NASA/Johns Hopkins University Applied Physics Laboratory/Carnegie Institution of Washington
The Spring of 2015 saw the successful end of MESSENGER’s operational mission, after the spacecraft crashed into Mercury’s surface at about 8,750 mph and created a new crater on the planet’s surface. During the mission’s three plus years of orbital operations, MESSENGER (a.k.a “MErcurySurface, Space ENvironment, GEochemistry, and Ranging mission”) snapped over 200,000 photographs of Mercury. Prior to this mission, only 45% of the surface of Mercury had been photographed by a spacecraft. Below is a compilation by NASA of the best images of 2014.
(From left to right)
The hollows-covered floor of Kertesz, located near the center of this image, distinguishes it from the other craters in this enhanced-color scene. A 3-kilometer crater also features prominently in this image despite its small size, due to its extensive set of young, bright rays. Both of these features are located on the floor of the great Caloris basin, which is a host to a variety of interesting tectonic features, including the troughs visible on the east side of this image.
The four-image mosaic shown here is one of the first from the MDIS low-altitude imaging campaign. Among the details revealed are hollows that appear to have formed in one layer in the wall of this 15-kilometer-diameter crater.
Small knobs and crater rims just barely catch the sunlight with the Sun low on Mercury’s eastern horizon. The relatively smooth floor of the Caloris basin is on the right, and the rim and exterior of the basin are to the left. The knobby texture outside of the basin may be the result of blocks of material that were ejected by the basin-forming impact.
Ever since MESSENGER entered orbit about Mercury in 2011, the dark impact melt flow of Waters crater has been a feature of interest. Targeted color imaging showed the distinctive blue color of the impact melt flow, inspiring the crater to be named for blues legend Muddy Waters in 2012. In 2013, this high-resolution image was acquired, revealing stunning new details of the impact melt flow beyond those visible previously.
The troughs of Raditladi are the focus of this high-resolution view inside the peak-ring basin. The troughs, which are largely concentric to the basin, formed through extensional stresses that caused portions of the floor to pull apart. Such extensional features are similar to those observed within Caloris. Some of the small, bright craters that dot Raditladi’s floor may be secondaries from Fonteyn crater approximately 900 km away, whose rays appear to cross the basin.
This image features a stunning view of two complex craters within the Calorisbasin. The floor of Sander crater is covered with bright hollows, while Munch crater stands out due to its low-reflectance crater rim.
The top image is a MASCS VIRS interpolated color composite of craters Eminescu, 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.
This high-resolution image features hollows within an unnamed crater. Hollows often have bright halos and usually form in or around craters. Here, the hollows are forming on the crater floor, along the base of the crater wall, and on the top of the central peak.
Hemingway crater is seen in this color view of Mercury’s surface. Hemingway is the 130-km (81-mile) diameter crater with a relatively brown floor and small patch of dark blue in its center. This impact crater has irregular depressions on its floor, which are fairly common in other impact craters and may be due to explosive volcanic events, but the low-reflectance, blue patch on the floor may point to a more complex history.
The interior of the Caloris basin has undergone complex tectonic modification. The prominent graben towards the bottom of the image lies just south of the crater Apollodorous near the center of Caloris. It is one of the largest graben in Pantheon Fosse.
This image reveals the surfaces within some of Mercury’s most prominent ice-bearing craters; from left to right, across the center of the image, the craters are Chesterton, Tryggvadóttir, and Tolkien. The same image is shown twice, but the one on the right has been stretched to reveal the permanently shadowed floors of the craters.
This stunning limb view includes the northeastern portion of the Caloris basin in the foreground. Poe crater, a large, dark-rimmed crater, lies along the lower left edge of the image. Ailey crater’s bright rays can be seen towards the center of the image. Balanchine crater’s hollow-covered floor is located near the lower right corner of the image.