Impact craters and basins, their numerous secondary craters, and heavily to lightly cratered plains are the characteristic landforms of the region. At least six multiringed basins ranging from 150 km to 440 km in diameter are present, Mercury I includes 75 whole-frame photographs of the Kuiper quadrangle, Mercury II,13 whole-frame photographs, and Mercury III,70 quarter-frame photographs. The photographs include 19 stereopairs in the part of the quadrangle. The most distant of the photographs was taken at an altitude of 89,879 km, therefore, varies widely but ranges from about 1.5 to 2.0 km over most of the area. A wide range of viewing and solar illumination angles precludes a high degree of mapping consistency. The easternmost 10° of the quadrangle is beyond the evening terminator, a low angle of solar illumination and a high viewing angle make possible discrimination of topographic detail near the terminator. Higher angles of illumination and lower viewing angles make it increasingly difficult to discern topographic variations to the west.
Many geologic units cannot be identified because of unfavourable viewing geometry west of approximately 55 deg. Mapping methods and principles are adapted from those developed for lunar photogeologic mapping, a photomosaic map of the best available photographs aided greatly in geologic interpretation and mapping. The rock units are subdivided into three groups, plains materials, terra materials, and crater and basin materials. The oldest rocks exposed in the quadrangle are the plains material. Collectively, these form a relatively subdued terrain of moderate relief. They are similar to some of the rolling and hilly terra and hilly and pitted materials in the lunar highlands, particularly in the Purbach. The intercrater plains unit is marked by the soft outlines of numerous overlapping secondary craters producing a subdued hummocky texture. Much of its surface is covered by a relatively thick regolith of reworked impact breccias. The cratered plains material is relatively flat with broad ridges and lobate scarps that in places resemble those of some of the lunar maria and it is difficult to obtain reliable crater counts on this unit because many secondary craters cannot be distinguished from primary craters.
Cratered plains materials embay craters in classes c1 to c3, they may represent lava flows extruded after an initial phase ofimpact flux. The albedo of the plains is intermediate compared to that of other mercurian units, but higher than that of the lunar maria
The Arecibo Observatory is a radio telescope in the municipality of Arecibo, Puerto Rico. This observatory is operated by SRI International, USRA and UMET, the observatory is the sole facility of the National Astronomy and Ionosphere Center, which refers to the observatory, and the staff that operates it. From its construction in the 1960s until 2011, the observatory was managed by Cornell University and it is used in three major areas of research, radio astronomy, atmospheric science, and radar astronomy. Scientists who want to use the observatory submit proposals that are evaluated by an independent scientific board, the observatory has appeared in film and television productions, gaining more recognition in 1999 when it began to collect data for the SETI@home project. It has been listed on the American National Register of Historic Places starting in 2008 and it was the featured listing in the National Park Services weekly list of October 3,2008. The center was named an IEEE Milestone in 2001 and it has a visitor center that is open part-time.
The main collecting dish is 305 m in diameter, constructed inside the left by a karst sinkhole. The dish surface is made of 38,778 perforated aluminum panels, each about 3 by 6 feet, the ground beneath is accessible and supports shade-tolerant vegetation. The observatory has four transmitters, with effective isotropic radiated powers of 20 TW at 2380 MHz,2.5 TW at 430 MHz,300 MW at 47 MHz. The reflector is a reflector, not a parabolic reflector. To aim the device, the receiver is moved to intercept signals reflected from different directions by the dish surface of 270 m radius. A parabolic mirror would have varying astigmatism when the receiver is off the focal point, the platform has a rotating, bow-shaped track 93 m long, called the azimuth arm, carrying the receiving antennas and secondary and tertiary reflectors. This allows the telescope to observe any region of the sky in a cone of visibility about the local zenith. Puerto Ricos location near the Northern Tropic allows Arecibo to view the planets in the Solar System over the Northern half of their orbit.
The round trip time to objects beyond Saturn is longer than the 2.6 hour time that the telescope can track a celestial position. The origins of the trace to late 1950s efforts to develop anti-ballistic missile defences as part of the newly formed ARPAs ABM umbrella-effort. Even at this stage it was clear that the use of radar decoys would be a serious problem at the long ranges needed to successfully attack a warhead. Among the many Defender projects were several studies based on the concept that a nuclear warhead would cause unique physical signatures while still in the upper atmosphere
The Shakespeare quadrangle is a region of Mercury running from 90 to 180° longitude and 20 to 70° latitude. Prior to the images taken by MESSENGER, the spacecraft images of Mercury were those taken by the Mariner 10 spacecraft. Most images used in mapping the geology of the Shakespeare quadrangle were taken during the near-equatorial first pass, the second, south-polar pass did not image the Shakespeare quadrangle at high resolution. High-resolution images of areas within the quadrangle were obtained during the third pass. All of the Mariner 10 passes occurred under similar lighting conditions, across the Shakespeare quadrangle, these conditions varied from low light at the terminator near the west boundary to higher sun at the east boundary. Consequently, lighting conditions were favorable for determining fine-scale relief in the west, albedo features such as bright crater rays, which are conspicuous in the eastern part, become increasingly difficult to recognize westward toward the terminator.
The average resolution of the pictures used from the first pass is just over 1 km, the dominant feature in the Shakespeare quadrangle is the Caloris Basin,1,300 km in diameter. This impact basin is the largest and best preserved on the hemisphere of Mercury observed by Mariner 10, surrounding Caloris is a discontinuous annulus of its ejecta deposits, called the Caloris Group. Caloris ejecta are embayed and partly covered by a unit that lies mostly in large, roughly circular depressions. This plains material occurs in the floors of old craters. The eastern part of the Shakespeare quadrangle consists mainly of cratered terrain, over the whole of the mapped area are scattered fresh craters superposed on other units, in the eastern part the large fresh craters show well- developed bright rays. The oldest recognizable unit in the quadrangle is the plains material. These plains were originally described by Trask and Guest as intercrater plains, the unit has a surface expression of rolling to hummocky plains in the areas between large craters and is exposed mainly in the eastern part of the mapped area.
Trask and Guest concluded that the surface of these represents a primordial surface of Mercury on which craters have been superposed. Because of this high gravity, considerable areas were unaffected by crater, in several parts of the quadrangle, especially on the margins of large expanses of smooth plains materials, is a unit of smoother and less rolling plains that have a lower crater density. Following Schaber and McCauley, this unit is called intermediate plains material and it is difficult to map with precision because it grades into both the intercrater plains and the smooth plains. Also, its recognition depends on lighting conditions that vary across the mapped areas, the presence of this unit suggests that the plains-forming process spanned much of the early geologic history of Mercury and continued long after the peak of cratering. In the southern part of Sobkou Planitia, intermediate plains have a lower albedo than the adjacent plains, in some places, they may simply represent areas of intercrater plains that have been partly flooded by the younger smooth plains material
The Victoria quadrangle is a region on Mercury from 0 to 90° longitude and 20 to 70 ° latitude. It is designated the H-2 quadrangle, and is known as Aurora after a large albedo feature. As is common with most of the portions of Mercury. At the time the pictures were obtained, the terminator was at about long 7° to 8°, a large gap in coverage between the incoming and outgoing images appears as a northeast-trending diagonal blank strip on the base map. A small part of this gap was filled in the part of the quadrangle by very poor second-encounter images. No images provide a view, in fact, the smallest angle between the planetary surface normal and the camera axis is about 50°. The high obliquity of the images, the range in sun-elevation angles. Only in about 15 percent of the quadrangle, near the southeast corner, three widespread units are recognized within the Victoria quadrangle. These are, from oldest to youngest, intercrater plains material, intermediate plains material, in addition, central peak, floor and ejecta materials related to the numerous craters and basins larger than about 20 km in diameter are mapped.
About half of the area consists of material characterized by a very high density of small, mostly degraded craters. Superposition relations suggest that this unit is about the age as, or older than, all mappable craters. Some of the more plainslike areas included within this unit may well have a similar to that of intermediate plains material. Within the 5° overlap area with the Kuiper quadrangle to the south, an area has been mapped that displays moderately rough to rough terrain and this unit is very similar to intercrater plains material, and cannot be distinguished from it anywhere else in the Victoria quadrangle. Most of the plains material is probably volcanic in origin. Smooth to moderately irregular plains occupy most of the area between large craters not underlain by intercrater plains material and these plains superficially resemble the plains of the lunar maria, they generally have a relatively low albedo and are characterized by numerous elongate ridges. Like the lunar maria, the two younger mercurian plains units have been ascribed to volcanic activity, although this interpretation has been questioned, a volcanic origin seems most probable, but no compelling evidence exists in the Victoria quadrangle to support this opinion.
The elongate ridges, though associated with intermediate plains material, are not restricted to it. Partly filling most craters is plains material that is smoother and less cratered than intermediate plains material
At least four such basins, now nearly obliterated, have largely controlled the distribution of plains materials and structural trends in the map area. Many craters, interpreted to be of impact origin, display a spectrum of modification styles, the interaction between basins and plains in this quadrangle provides important clues to geologic processes that have formed the morphology of the mercurian surface. Several low-albedo features are evident in Earth-based views of the Michelangelo quadrangle, Solitudo Promethei may correspond to a deposit of plains materials centered at –58°, 135°, and Solitudo Martis may correspond to similar materials at –30° to –40°, 90° to 100°. The color data presented in Hapke and others show no particular correlation with mapped terrain types. The “yellow” region centered at –33°, 155° appears to correspond to a smooth plains deposit, mariner 10 data include complete photographic coverage of the quadrangle at a resolution of about 2 km. In addition, twelve stereopairs cover scattered areas in the quadrangle, systematic mapping of the Michelangelo quadrangle has revealed the presence of four nearly obliterated multiring basins.
These basins are here named for unrelated superposed, named craters, because none of the four basins has ejecta deposits that are preserved, the basins are assumed to be the oldest features in the map area, they are embayed or buried by all other units. The figures for the ages of the basins are based on the density of superposed primary impact craters. These results are uncertain, as the density of heavily cratered terrain on Mercury ranges from 11.2 to 17.4 × 10-5 km-2 for craters of diameters 20 km or greater. The results obtained are consistent with an assignment of relative age that is based on position. The basins have largely controlled subsequent geologic processes in the map area, large concentrations of smooth plains deposits are found within the basin boundaries and at the intersections of rings of different basins. These relations have noted for ancient basins on both the Moon and Mars. In addition to the four multiring basins, an ancient two-ring basin, Surikov, is evident at –37°.
This morphology is similar to that of the lunar basin Grimaldi and is suggestive ofan extended period of structural rejuvenation along the margins of the inner ring. This material is generally undulating to hummocky and appears to underlie tracts of cratered terrain, in some areas, the intercrater plains material appears to embay c1 craters, and it is found in all of the degraded basins described above. The origin of mercurian intercrater plains material remains unknown, both volcanic and impact-debris models have been proposed. The material is most likely polygenetic, including both crater and basin debris and possibly ancient volcanic flows and lithologically it resembles the lunar highlands megaregolith. At least seven basins in or partly in the Michelangelo quadrangle postdate or are contemporaneous with the last stages of deposition of intercrater plains material, Dostoevskij displays only one ring, presumably the inner peak ring is buried by plaint material
Adventure Rupes is an escarpment on Mercury approximately 270 kilometers long located in the southern hemisphere of Mercury. Discovered by the Mariner 10 spacecraft in 1974, it was formed by a thrust fault, Adventure Rupes has an arcuate shape with the scarp face on convex side of the arc. It has a relief of about 1.3 km and is a continuation of Resolution Rupes and Discovery Rupes along a rough arc, Adventure Rupes is separated from Resolution Rupes by a high relief ridge informally named Rabelais Dorsum, which crosscuts the scarps. This means that Resolution Rupes and Adventure Rupes may be parts of one large structure similar in length to Discovery Rupes, the scarp is named after HMS Adventure, one of James Cooks ships on second voyage to the Pacific, 1772–75
Caloris Planitia is a plain within a large impact basin on Mercury, informally named Caloris, about 1,550 km in diameter. It is one of the largest impact basins in the Solar System, calor is Latin for heat and the basin is so-named because the Sun is almost directly overhead every second time Mercury passes perihelion. The crater, discovered in 1974, is surrounded by a ring of mountains approximately 2 km tall, Caloris was discovered on images taken by the Mariner 10 probe in 1974. It was situated on the line dividing the daytime and nighttime hemispheres—at the time the probe passed by. Later, on January 15,2008, one of the first photos of the planet taken by the MESSENGER probe revealed the crater in its entirety. The basin was estimated to be about 810 mi in diameter. It is ringed by mountains up to 2 km high, inside the crater walls, the floor of the crater is filled by lava plains, similar to the maria of the Moon. These plains are superposed by explosive vents associated with pyroclastic material, outside the walls, material ejected in the impact which created the basin extends for 1,000 km, and concentric rings surround the crater.
In the center of the basin is a region containing numerous radial troughs that appear to be extensional faults, the exact cause of this pattern of troughs is not currently known. The feature is named Pantheon Fossae, the impacting body is estimated to have been at least 100 km in diameter. Bodies in the inner Solar System experienced a heavy bombardment of large bodies in the first billion years or so of the Solar System. Based on MESSENGERs photographs, Caloris age has been determined to be between 3.8 and 3.9 billion years, the giant impact believed to have formed Caloris may have had global consequences for the planet. At the exact antipode of the basin is an area of hilly, grooved terrain. It is thought by some to have created as seismic waves from the impact converged on the opposite side of the planet. Alternatively, it has suggested that this terrain formed as a result of the convergence of ejecta at this basin’s antipode. This hypothetical impact is believed to have triggered volcanic activity on Mercury.
Surrounding Caloris is a series of geologic formations thought to have produced by the basins ejecta. Mercury has a tenuous and transient atmosphere, containing small amounts of hydrogen and helium captured from the solar wind
The Discovery quadrangle lies within the heavily cratered part of Mercury in a region roughly antipodal to the 1550-km-wide Caloris Basin. Interspersed with the craters and basins both in space and time are plains deposits that are probably of several different origins, because of its small size and very early segregation into core and crust, Mercury has seemingly been a dead planet for a long time—possibly longer than the Moon. Its geologic history, records with considerable clarity some of the earliest and most violent events took place in the inner Solar System. As on the Moon and Mars, sequences of craters and basins of differing relative ages provide the best means of establishing stratigraphic order on Mercury, overlap relations among many large mercurian craters and basins are clearer than those on the Moon. Therefore, we can build up many local stratigraphic columns involving both crater or basin materials and nearby plains materials. Over all of Mercury, the crispness of crater rims and the morphology of their walls, central peaks, ejecta deposits, the youngest craters or basins in a local stratigraphic sequence have the sharpest, crispest appearance.
The oldest craters consist only of shallow depressions with raised, rounded rims. On this basis, five age categories of craters and basins have been mapped, tracts of plains materials range in size from a few kilometers across to intercrater areas several hundred kilometers in width. This material is not all of the same origin. Strom and others and Trask and Strom cited evidence that large areas of plains are of volcanic origin. Smaller tracts are more apt to be impact melt, loose debris pooled in low spots by seismic shaking, the origin of many individual tracts must necessarily remain uncertain without additional information. Plains materials have been grouped into four units on the basis of both the density of super-posed craters and the relation of each unit to adjacent crater and basin materials and these units are listed as follows from oldest to youngest. Contacts between intercrater plains and intermediate plains units that occur outside mapped craters and basins are gradational, smooth plains material occurs in relatively small patches throughout the quadrangle on the floors of c4 and older craters and basins and in tracts between craters.
More bright-halo craters occur on this unit than on either the inter-crater plains or intermediate plains units, very smooth plains material occurs on the floors of some of the youngest craters. In summary, a history of contemporaneous formation of craters, basins. The Discovery quadrangle includes some of the most distinctive relief-forming material on the planet, the unit consists of a jumble of evenly spaced hills and valleys about equal in size. The hilly and lineated unit and the enclosed hummocky plains unit appear to be relatively young, in addition, they lie almost directly opposite that basin on the planet. Morphologically diverse scarps, ridges and other structural lineaments are relatively common in the Discovery quadrangle, Dzurisin documented a well-developed pattern of linear lithospheric fractures in the quadrangle that predate the period of heavy bombardment
The Tolstoj quadrangle in the equatorial region of Mercury runs from 144 to 216° longitude and -25 to 25° latitude. It was provisionally called Tir, but renamed after Leo Tolstoy by the International Astronomical Union in 1976 and it contains the southern part of Caloris Planitia, which is the largest and best preserved basin seen by Mariner 10. This basin, about 1550 km in diameter, is surrounded by a discontinuous annulus of ejecta deposits of the Caloris Group that are embayed and covered by broad expanses of smooth plains. The ancient and degraded Tolstoj multiring basin, about 350 km in diameter, is in the part of the quadrangle. The “hot pole” at 180° lies within the Tolstoj quadrangle, at perihelion and this daily range of 600 K is greater than that on any other body in the solar system. Mariner 10 photographic coverage was available for only the eastern two-thirds of the Tolstoj quadrangle, image data from three Mariner 10 encounters with Mercury were used in mapping the quadrangle.
The rolling to hummocky plains that lie between large craters in the part of the quadrangle make up the oldest recognizable map unit. Malin showed the plains to contain highly eroded remnants of large craters, superposition of crater ejecta over parts of intercrater plains in other areas indicates that some large craters formed in a preexisting intercrater plains unit. On the other hand, the plains material partly postdates some of the major cratering events on Mercury. A complex history of contemporaneous craters and plains formation is therefore suggested, a detailed discussion of the origin of the intercrater plains on the Moon and Mercury was given by Strom. Patches of less cratered, less rolling plains occur throughout the quadrangle, because their distribution cannot now be mapped accurately, many of these patches are included with the smooth plains material. Certain patches of these plains, where clearly rougher and possibly older, are mapped as the intermediate plains material. The impact that produced the Tolstoj Basin occurred very early in the history of the quadrangle, diffuse patches of material of dark albedo lie outside the innermost ring.
The central part of the basin is covered by smooth plains material, the ejecta tends to be blocky and only weakly lineated between the inner and outer rings. Radial lineations with a slight swirly pattern are best seen on the southwest side of Tolstoj, analysis of stereo- photography of Tolstoj ejecta northeast of the crater suggests that this deposit has been upwarped to a higher elevation relative to the surrounding plains. The Caloris Basin is especially significant from a stratigraphic standpoint, like the Imbrium and Orientale Basins on the Moon, it is surrounded by an extensive and well-preserved ejecta blanket. As on the Moon, where ejecta from the better preserved basins was used to construct a stratigraphy and this ejecta is recognizable to a distance of about one basin diameter in the Tolstoj quadrangle and the adjacent Shakespeare quadrangle to the north. Undoubtedly, the ejecta influences a large part of the terrain to the west
The Borealis quadrangle is a quadrangle on Mercury surrounding the north pole down to 65° latitude. The west half of the area is dominated by older craters. Younger crater materials, intermediate plains material, and small patches of plains material are superposed on all other units. The crater Verdi,122 km in diameter, is the largest of the younger craters and its extensive ejecta blanket and secondary crater field are superposed on plains materials and older craters. The east half of the area is characterized by smooth plains material. This unit covers vast expanses of Borealis Planitia, a depression about 1,000 km in diameter that has an irregular arcuate west boundary and this depression is located over the site of one or several old impact structures. Most of the used for geologic mapping were acquired by the departing spacecraft during the first pass. The Mercury II encounter provided no usable images of the map area, no stereoscopic photographic pairs are available for the Borealis region.
Because the terminator was a few degrees away from the 0°-180° meridian at the time of the first encounter, photographs of the region were acquired under a wide range of lighting conditions. Mercurys equatorial plane is inclined less than 2° to its orbital plane, the resulting lag and orbital eccentricity create a variation of mean temperature not only with latitude, as on the Earth, but with longitude. Further, conservation of angular momentum and spin-orbit coupling cause considerable variation in the length of daylight. Despite these considerations and despite the range in surface temperatures of several hundred kelvins. Within the Borealis region, three widespread plains units are recognized largely by their obvious differences in density, which is closely related to relative age. From most heavily cratered to least cratered, these units are intercrater plains material, intermediate plains material, visual identification is confirmed and refined by actual crater counts. The curve for the uplands was derived from crater counts in the region northwest of crater Tsiolkovskiy.
The curve for the part of Oceanus Procellarum was obtained in an area centered near lat 2°00 N. Material of Borealis Planitia was not included in the smooth plains count because images of the area were blurred by spacecraft motion, and so reliable crater counts could not be obtained. However, smooth plains south of lat 65° N. in the Shakespeare quadrangle, in the crater Strindberg, the plains materials that lie outside Borealis Planitia are distributed in irregular belts, which are subparallel to the terminator and to one another