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Craters caused by impacts on Mercury. These can be cut through by scarps (possibly compressed in the process) or covered over by volcanic ejecta. Some have long bright rays, while others have long dark rays. The transitional diameter of craters (10-12 km) between simple (bowl-shaped) and complex craters (central peaks and ridges) is twice that of Mars, despite the fact that surface gravity at both planets are roughly the same. The fact that the average impact speed is 2-3 times greater than that of Mars may be a contributing factor.
Specific Craters[]
Impact Basins:
- Caloris Basin - The largest impact basin on Mercury and one of largest in Solar System. Discovered by Mariner 10, which only imaged half of it. First image of Mercury sent by Messenger was centered on this basin. As opposed to lunar basins, which are filled with dark material, Caloris is filled with light plains, which has not been explained yet. MESSENGER found titanium oxide in a region northwest of here.
- Rembrandt Basin - The second largest impact basin on Mercury discovered by MESSENGER during its second flyby. Formed 3.9 BYA (young for a large basin). Lava only flowed in the central region, unlike most similar basins. A unique formation of spoked ridges also appears in the basin. The largest fault on the planet runs through this basin. The only basin with its original impact floor exposed which have not been obliterated by subsequent vulcanism.
- Rachmaninoff Basin - A large double-rimmed impact basin on Mercury, 180 miles in diameter. One of the youngest seen. First seen in its entirety during Messenger's third flyby. Its floor has been resurfaced with the most recent volcanism detected on the planet so far and the youngest volcanic surface, probably under 2 billion years old. These plains differ in color than the surrounding area. A volcanic vent was discovered to the north of the crater. The impact may have risen the temperature of the mantle area to the melting point, which spurred the vulcanism. Fourth crater found (after Caloris, Rembrandt, and Raditladi) to have extensive tectonic features, which are of unknown origin.
Craters:
- Degas Crater - Crater on Mercury initially observed by Mariner 10. As it cooled, cracks formed across it.
- Debussy Crater - A large crater on Mercury whose rays extend across much of the southern hemisphere. It was first discovered by radar observations from the Goldstein observatory and initially dubbed Feature A. It was first photoed by Messenger during a flyby and subsequently given a name. It was the dominant feature in the first photo from the Messenger probe from orbit.
- Matabei Crater - A crater on Mercury with rare dark rays. It was visible in Messenger's first photos sent from orbit.
- Hokusai Crater - Large, young, and bright-rayed crater on Mercury. Initially detected with radar at the Goldstone Observatory, it was dubbed Feature B and originally thought to be a volcano.