Mare Smythii (

Latin Latin (, or , ) is a classical language belonging to the Italic branch of the Indo-European languages. Latin was originally a dialect spoken in the lower Tiber area (then known as Latium) around present-day Rome, but through the power ...

for "Smyth's Sea") is a lunar mare located along the equator on the easternmost edge of the

Moon The Moon is Earth's only natural satellite. It is the fifth largest satellite in the Solar System and the largest and most massive relative to its parent planet, with a diameter about one-quarter that of Earth (comparable to the width ...

's near side. It is named for the 19th-century British astronomer

William Henry Smyth Admiral William Henry Smyth (21 January 1788 – 8 September 1865) was a Royal Navy officer, hydrographer, astronomer and numismatist. He is noted for his involvement in the early history of a number of learned societies, for his hydrographic ...

. The Smythii basin where the mare is located is of the Pre-Nectarian

epoch In chronology and periodization, an epoch or reference epoch is an instant in time chosen as the origin of a particular calendar era. The "epoch" serves as a reference point from which time is measured. The moment of epoch is usually decided by ...

, while the surrounding features are of the Nectarian system. It is contained within a minimal diameter of , and has been excavated to a depth of . The mare material, which makes up the floor of the mare, is a low alumina

basalt Basalt (; ) is an aphanitic (fine-grained) extrusive igneous rock formed from the rapid cooling of low-viscosity lava rich in magnesium and iron (mafic lava) exposed at or very near the surface of a rocky planet or moon. More than 90% of a ...

, and consists of

Upper Imbrian The Imbrian is a lunar geologic period divided into two epochs, the Early and Late. Early Imbrian In the lunar geologic timescale, the Early Imbrian epoch occurred from 3,850 million years ago to about 3,800 million years ago. It overlaps the end ...

basalt covered by Eratosthenian basalt. Features observed within the basin include wrinkle ridges, submerged "ghost" craters, domes, crater chains, and

rille Rille (German for 'groove') is typically used to describe any of the long, narrow depressions in the surface of the Moon that resemble channels. The Latin term is ''rima'', plural ''rimae''. Typically, a rille can be several kilometers wi ...

s. The overall shape of the mare is circular, likely the result of a large impact. Further bombardment followed, creating the irregular shape. Subsequent volcanism laid down the mare material. As a result of this sequence, only the northeastern portion and a smaller area in the western central contain significant regions of smooth mare material. The remaining surface is more hummocky with a higher albedo. The geological features suggest that lava flowed from the southeast and west toward the northeast, where it accumulated in the lowest parts of the basin. Mare Smythii contains a relatively high number of craters with fractured floors, including the noticeably unusual crater Haldane. This is probably a result of uplift from injection of magma below the mare. The crater Neper is located to the north of the mare. This crater makes up part of the southern rim of Mare Marginis. Just off to the northwest of the mare are the craters

Schubert Franz Peter Schubert (; 31 January 179719 November 1828) was an Austrian composer of the late Classical and early Romantic eras. Despite his short lifetime, Schubert left behind a vast ''oeuvre'', including more than 600 secular vocal wor ...

and Schubert B. The dark mare-filled crater at the southern edge of Smythii is the crater

Kästner Kästner (transliterated Kaestner) is a German surname. Notable people with the surname include: * Abraham Gotthelf Kästner, (1719-1800), German mathematician ** Kästner (crater), a lunar crater * Detlef Kästner (born 1958), German boxer * Erich ...

Gallery

File:MareSmithiiTG.jpg, The topography (top) and corresponding gravity (bottom) signal of Mare Smythii reveals a mascon in its center File:Smythii basin topo.jpg, Topographic map File:Smythii basin GRAIL gravity.jpg, Gravity map based on GRAIL File:Mare Smythii AS10-27-3915.jpg, View from

Apollo 10 Apollo 10 (May 18–26, 1969) was a human spaceflight, the fourth crewed mission in the United States Apollo program, and the second (after Apollo8) to orbit the Moon. NASA described it as a "dress rehearsal" for the first Moon landing, an ...

File:Mare Smythii AS16-M-3008.jpg, Oblique view from Apollo 16

References

{{Lunar maria Smythii Smythii Smythii Smythii