An impact crater is a depression in the surface of a solid astronomical body formed by the hypervelocity impact of a smaller object. 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 are typically circular, though they can be elliptical in shape or even irregular due to events such as landslides. Impact craters range in size from microscopic craters seen on lunar rocks returned by the Apollo Program to simple bowl-shaped depressions and vast, 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. In the Solar System it is the third-largest moon after Ganymede and Saturn's largest moon Titan, and nearly as large as the smallest planet Mercury. Callisto is, with a diameter of 4,821 km, roughly a third larger than Earth's Moon and orbits Jupiter on average at a distance of 1,883,000 km, which is about five times further out than the Moon orbiting Earth. It is the outermost of the four large Galilean moons of Jupiter, which were discovered in 1610 with one of the first telescopes, and is today visible from Earth with common binoculars.
Ganymede, or Jupiter III, is the largest and most massive natural satellite of Jupiter, and in the Solar System. Despite being the only moon in the Solar System with a substantial magnetic field, it is the largest Solar System object without a substantial atmosphere. Like Saturn's largest moon Titan, it is larger than the planet Mercury, but has somewhat less surface gravity than Mercury, Io, or the Moon due to its lower density compared to the three. 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 in 1935. 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.
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 and 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 percent 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 716 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 that has been degraded over time. They may also be referred to as "ghost craters", "degraded craters", "buried craters", or "pathological craters". Palimpsests have been identified on Mercury, the Earth, the Moon, Mars, Ganymede, Callisto, and possibly even Titan. On Mars, these features are morphologically described as craters that are "flat-floored, rimless, extremely shallow, without central peaks, and would probably represent what remains after erosion."
A low-aspect-ratio layered ejecta crater is a class of impact crater found on the planet Mars. This class of impact craters was discovered by Northern Arizona University scientist Professor Nadine Barlow and Dr. Joseph Boyce from the University of Hawaii in October 2013. Barlow described this class of craters as having a "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", Barlow said. The scientists used data from continuing reconnaissance of Mars using the old Mars Odyssey orbiter and the Mars Reconnaissance Orbiter. They discovered 139 LARLE craters ranging in diameter from 1.0 to 12.2 km, with 97% of the LARLE craters found poleward of 35N and 40S. The remaining 3% 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 resembling rings on a bull's-eye. A multi-ringed basin may have an area of many thousands of square kilometres.
Tectonic activity has been studied on several icy moons.
Pharos is the largest known impact crater on Neptune's moon Proteus. It is named after the island of Pharos, making it the only named surface feature on Proteus as of 2024. It measures 10–15 km deep and has a diameter of around 250 km (160 mi), making it more than half the diameter of Proteus itself. Debris ejected from the impact that created Pharos may have formed Hippocamp, a small moon whose orbit is unusually close to Proteus's.
