Mare Smythii

Mare Smythii, Latin for “Smyth’s Sea,” is a basaltic plain on the Moon located near the lunar equator at the easternmost edge of the near side. It is a lunar mare rather than a commercial brand or corporate entity. The feature takes its name from William Henry Smyth, a nineteenth-century British astronomer, and is one of only two lunar maria named after people; the other is Mare Humboldtianum, named after the German explorer Alexander von Humboldt. The mare occupies the Smythii impact basin, a large circular geological structure with a minimum diameter of approximately 373.97 kilometres. The basin floor was excavated to a depth of about four kilometres during the original impact event. Geological interpretations place the basin in the Pre-Nectarian epoch, while many surrounding features belong to the Nectarian system. After the basin formed, later bombardment modified its rim and interior. Subsequent volcanic activity flooded parts of the basin with basaltic mare material. The mare's floor contains low-alumina basalt. The volcanic sequence includes Upper Imbrian basalt overlain by younger Eratosthenian basalt. Lava appears to have flowed from the southeast and west toward the northeast, where it accumulated in the lowest portions of the basin. Consequently, smooth mare deposits are concentrated mainly in the northeastern part of the feature and in a smaller area of the western central basin. Much of the remaining terrain is more hummocky and has a relatively higher albedo. Mare Smythii preserves a varied collection of volcanic and impact-related landforms. These include wrinkle ridges, partially submerged or “ghost” craters, volcanic domes, crater chains, and rilles. It also has an unusually high concentration of craters with fractured floors. Haldane is a particularly notable example; the fractured floors are interpreted as possibly resulting from uplift caused by magma injected beneath the mare. Several named lunar features help define Mare Smythii's setting. The prominent Bandfield lunar cold spot lies to its southwest. Neper crater is situated to the north and forms part of the southern rim of Mare Marginis. The craters Schubert and Schubert B lie just northwest of the mare, while Kästner, a dark mare-filled crater, marks the southern edge. Together, these features provide geographic and geological context for one of the Moon's more distinctive impact-basin maria.

Mare Smythii is a lunar mare formed within the Smythii basin on the Moon's near side. Its geological history begins with a major impact during the Pre-Nectarian epoch. The impact created a broad, roughly circular basin and excavated material from several kilometres beneath the lunar surface. The initially regular structure was later altered by additional impacts, which produced an irregular interior and rim and added numerous craters to the basin. After the principal basin-forming event and subsequent bombardment, volcanic activity filled portions of the depression with basaltic lava. The mare floor is characterized by low-alumina basalt and records at least two broad episodes of emplacement: Upper Imbrian basalt followed by Eratosthenian basalt. These episodes transformed parts of the impact basin into a dark, relatively smooth plain, although lava did not cover the entire interior uniformly. The distribution of mare material indicates that lava moved from the southeast and west toward the northeast. The lowest parts of the basin therefore accumulated the most extensive smooth deposits. The northeastern sector contains the largest continuous area of smooth mare surface, while a smaller smooth region occurs in the western central basin. Elsewhere, older or less completely flooded terrain remains more uneven and generally brighter in appearance. Later geological processes continued to modify the surface. Impacts created craters, crater chains, and partially buried “ghost” craters. Volcanic and tectonic activity produced wrinkle ridges, domes, and rilles. A notable characteristic of the basin is its comparatively large number of craters with fractured floors. Haldane crater is an important example. Such fractures may reflect the upward movement of the crater floors after magma was injected beneath them, indicating that the basin experienced post-impact internal activity rather than remaining geologically inert after lava emplacement. The surrounding lunar geography places Mare Smythii near several important features. Neper crater lies north of the mare and helps define the southern rim of Mare Marginis. Schubert and Schubert B are located northwest of the basin, while Kästner crater occupies the southern edge. Bandfield, a prominent lunar cold spot, lies southwest. Mare Smythii's name commemorates William Henry Smyth, a nineteenth-century British astronomer. Its human-derived name is unusual among lunar maria, being shared only with Mare Humboldtianum.

• Formation of the Smythii impact basin

  [1]Mare Smythiien.wikipedia.org

  A major impact during the Pre-Nectarian epoch created the broad basin in which Mare Smythii is located and excavated the surface to a depth of approximately four kilometres.

• Emplacement of mare basalt

  [1]Mare Smythiien.wikipedia.org

  Later volcanic activity flooded parts of the basin with low-alumina basalt, including Upper Imbrian and Eratosthenian mare material.

• Recognition of the feature's eponym

  [1]Mare Smythiien.wikipedia.org

  The lunar mare received the name Mare Smythii, meaning “Smyth’s Sea,” in honour of British astronomer William Henry Smyth.

1. 1Mare Smythiien.wikipedia.org