Kuiper quadrangle
Inasmuch as multiringed basins occur widely on that part of Mercury photographed by Mariner 10, as well as on the Moon and Mars, they offer a potentially valuable basis for comparison between these planetary bodies.
The MESSENGER spacecraft orbited Mercury from 2011 to 2015 and mapped the planet in its entirety at much higher resolution and in more wavelengths of light than Mariner 10.
It obtained topographic, reflectance, magnetic, gravitational, and other types of geophysical data from orbit in addition to the photography.
A wide range (more than 50 deg) of both viewing and solar illumination angles precludes a high degree of mapping consistency.
The intercrater plains unit is commonly marked by the soft outlines of numerous overlapping secondary craters producing a subdued hummocky texture.
The cratered plains material is relatively flat with broad ridges and lobate scarps that in places resemble those of some of the lunar maria.
The albedo of the cratered plains is intermediate compared to that of other mercurian units, but higher than that of the lunar maria, and may reflect lower iron and titanium content.
Rough terra occurs as overlapping and intermixed ejecta blankets around dusters of large young craters in the eastern part of the quadrangle.
The relief here appears to be higher than elsewhere in the map area, and the occurrence of dense arrays of fresh secondary craters produces a coarsely textured, hummocky surface at a scale of about 10–20 km.
Ordinarily, rough terra material would be subdivided and mapped as individual ejecta blankets around and belonging to particular craters.
This frequency is comparable to that of the lunar maria near the Apollo 11 landing site (Greeley and Gault, 1970; Neukume et al., 1975; Meyer and Grolier, 1977).
A few patches of very dark material occur in the western part of the quadrangle where the sun angle is high and albedo contrasts are enhanced.
Under favourable lighting conditions, the youngest craters exhibit bright rays superposed on all older materials.
The major differences between mercurian and lunar craters are apparently related to the greater gravitational acceleration and the higher impact velocities on Mercury.
The interpretable geologic history of the Kuiper quadrangle is primarily a record of decreasing meteoroid flux during which large craters and basins formed and plains materials were deposited.
Approximately half of the mapped area contains a high density of craters and multiringed basins formed by the intense early bombardment.
The small size of Mercury, its lack of atmosphere, and the cratered nature of its surface invite comparison with the Moon.
Apparent differences may be the result of resolution of the imaging system, and small viewing and illumination angles that do not allow inspection of the surface under varied conditions.
Real differences may be the result of Mercury's size, gravitational field, proximity to the Sun, internal composition and structure, or timing of major volcanic episodes relative to the decrease in impact craters.
