An impact crater is an approximately circular depression in the surface of a planet, moon, or other solid body in the Solar System or elsewhere, formed by the hypervelocity impact of a smaller body. In contrast to volcanic craters, which result from explosion or internal collapse, impact craters typically have raised rims and floors that are lower in elevation than the surrounding terrain. Impact craters range from small, simple, bowl-shaped depressions to large, complex, multi-ringed impact basins. Meteor Crater is a well-known example of a small impact crater on Earth.
Callisto, or Jupiter IV, is the second-largest moon of Jupiter, after Ganymede. It is the third-largest moon in the Solar System after Ganymede and Saturn's largest moon Titan, and the largest object in the Solar System that may not be properly differentiated. Callisto was discovered in 1610 by Galileo Galilei. At 4821 km in diameter, Callisto has about 99% the diameter of the planet Mercury but only about a third of its mass. It is the fourth Galilean moon of Jupiter by distance, with an orbital radius of about 1883000 km. It is not in an orbital resonance like the three other Galilean satellites—Io, Europa, and Ganymede—and is thus not appreciably tidally heated. Callisto's rotation is tidally locked to its orbit around Jupiter, so that the same hemisphere always faces inward. Because of this, there is a sub-Jovian point on Callisto's surface, from which Jupiter would appear to hang directly overhead. It is less affected by Jupiter's magnetosphere than the other inner satellites because of its more remote orbit, located just outside Jupiter's main radiation belt.
Ganymede, a satellite of Jupiter, is the largest and most massive of the Solar System's moons. The ninth-largest object in the Solar System, it is the largest without a substantial atmosphere. It has a diameter of 5,268 km (3,273 mi) and is 8% larger than the planet Mercury, although only 45% as massive. Possessing a metallic core, it has the lowest moment of inertia factor of any solid body in the Solar System and is the only moon known to have a magnetic field. Outward from Jupiter, it is the seventh satellite and the third of the Galilean moons, the first group of objects discovered orbiting another planet. Ganymede orbits Jupiter in roughly seven days and is in a 1:2:4 orbital resonance with the moons Europa and Io, respectively.
Kittu crater is a crater on Jupiter's moon Ganymede. It is approximately 15 km (9.3 mi) in diameter.
Plato is a lava-filled lunar impact crater on the Moon. Its diameter is 101 km. It was named after ancient Greek philosopher Plato. It is located on the northeastern shore of the Mare Imbrium, at the western extremity of the Montes Alpes mountain range. In the mare to the south are several rises collectively named the Montes Teneriffe. To the north lies the wide stretch of the Mare Frigoris. East of the crater, among the Montes Alpes, are several rilles collectively named the Rimae Plato.
Located on Jupiter's moon Callisto, Valhalla is the largest multi-ring impact crater in the Solar System. It is named after Valhalla, the hall where warriors are taken after death in Norse mythology.
Boyle is a lunar impact crater that is located in the southern hemisphere on the rugged far side of the Moon. It is adjacent to the larger crater Hess to the southeast, and lies about midway between the craters Alder to the north-northeast and Abbe to the south-southwest.
Steinheil is a lunar impact crater that is located in the rugged highlands in the southeastern part of the Moon. It was named after German astronomer and physicist Carl August von Steinheil. It forms a prominent crater pair with the similar-sized Watt, which it partly overlies to the southeast. To the northwest is the large walled plain Janssen. Due to the location of this crater, it appears foreshortened when viewed from the Earth. It is from the Nectarian period, 3.92 to 3.85 billion years ago.
d'Alembert is a large lunar impact crater located in the northern hemisphere on the far side of the Moon, to the northeast of the somewhat smaller walled plain Campbell. Astride the southwest rim of d'Alembert is Slipher. To the north is the crater Yamamoto, and to the south-southwest lies Langevin. This walled plain has the same diameter as Clavius on the near side, making it one of the largest such formations on the Moon.
Chapman is a lunar impact crater that lies just beyond the northwest rim of the Moon, on the far side as seen from the Earth. It lies to the northeast of the crater Rynin, and southward of the large walled plain Poczobutt.
Chaplygin is a large lunar impact crater that lies on the far side of the Moon. It is located to the southeast of the huge walled plain Mendeleev, about midway between the craters Schliemann to the northeast and Marconi to the southwest. It is about the same size as Albategnius on the near side.
Santbech is a lunar impact crater that is located to the southeast of Mare Nectaris. It lies south-southwest of the prominent crater Colombo. About one crater diameter to the east-northeast is the smaller Monge. The terrain around the crater, although rugged in places, has been flooded by lava and so has a low albedo and a relatively flat surface. It was named after the 16th-century Dutch mathematician and astronomer Daniel Santbech Noviomagus. It is from the Pre-Imbrian period, 4.55 to 3.85 billion years ago.
Epimenides is a lunar impact crater that is located in the southwestern part of the Moon's near side, just to the east of the oddly shaped crater Hainzel. Just to the north and northeast is Lacus Timoris, a small lunar mare. The crater is 27 kilometers in diameter and 2,000 meters deep. It may be from the Pre-Nectarian period, 4.55 to 3.92 billion years ago.
Galileo Regio is a large, dark surface feature on Jupiter's moon Ganymede.
Memphis Facula is a palimpsest, or "ghost crater", on Ganymede, the largest of the Jovian satellites.
Lofn is a large relatively young impact crater on Jupiter's Galilean satellite Callisto. It was identified in 1997 and named after the goddess of marriage in Norse mythology. Located near the south pole of this moon, Lofn is classified as a flat floored or anomalous dome impact crater. It is superimposed on Adlinda multilayer structure obscuring about 30% of it. Another multi-ring structure—Heimdall is found to the south-west of Lofn.
Rembrandt is a large impact crater on Mercury. With a diameter of 715 km it is the second-largest impact basin on the planet, after Caloris, and is one of the larger craters in the Solar System. It was discovered by MESSENGER during its second flyby of Mercury on October 6, 2008. The crater is 3.9 billion years old, and was created during the period of Late Heavy Bombardment. The density and size distribution of impact craters along Rembrandt's rim indicate that it is one of the youngest impact basins on Mercury.
A palimpsest, in planetary astronomy, is an ancient crater on an icy moon of the outer Solar System whose relief has disappeared due to creep of the icy surface or subsequent cryovolcanic outpourings, leaving a circular albedo feature, perhaps with a "ghost" of a rim. Icy surfaces of natural satellites like Callisto and Ganymede preserve hints of their history in these rings. A typical example is Memphis Facula on Ganymede, a 340 km wide palimpsest.
A new class of Martian impact craters have been discovered by Northern Arizona University scientist Prof Nadine Barlow and Dr Joseph Boyce from the University of Hawaii in Oct 2013. They have termed it as ‘low-aspect-ratio layered ejecta (LARLE) craters’. Prof Nadine Barlow, a scientist Northern Arizona University described this class of craters with “thin-layered outer deposit” surpassing “the typical range of ejecta”. “The combination helps vaporize the materials and create a base flow surge. The low aspect ratio refers to how thin the deposits are relative to the area they cover,” Prof Barlow said. The scientists used data from continuing reconnaissance of Mars using the old Mars Odyssey Orbiter and the Mars Reconnaissance Orbiter, discovered 139 LARLE craters ranging in diameter from 1.0 to 12.2 km, with 97 per cent of the LARLE craters are found poleward of 35N and 40S, while remaining mainly traced in the equatorial Medusae Fossae Formation.
A multi-ringed basin is not a simple bowl-shaped crater, or a peak ring crater, but one containing multiple concentric topographic rings; a multi-ringed basin could be described as a massive impact crater, surrounded by circular chains of mountains. As such, a multi-ring basin slightly resembles a bull's-eye, may have an area of many thousands of square kilometres.
