Sinus Iridum (

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 of the ...

''sinus īridum'' "Bay of Rainbows") is a plain of

basalt Basalt (; ) is an aphanite, 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 planetary surface, surface of a terrestrial ...

lava Lava is molten or partially molten rock (magma) that has been expelled from the interior of a terrestrial planet (such as Earth) or a moon onto its surface. Lava may be erupted at a volcano or through a fracture in the crust, on land or un ...

that forms a northwestern extension to the

Mare Imbrium Mare Imbrium (Latin ''imbrium'', the "Sea of Showers" or "Sea of Rains", "Sea of Tears") is a vast lava plain within the Imbrium Basin on the Moon and is one of the larger craters in the Solar System. The Imbrium Basin formed from the colli ...

on Earth's

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 of ...

. It is surrounded from the northeast to the southwest by the

Montes Jura Montes Jura is a mountain range in the northwest part of the near side of the Moon. The selenographic coordinates of this range are 47.1° N 34.0° W. It has a diameter of 422 km, with mountains rising to approximately 3800m above the level o ...

range. The protruding part of the range at the southwest end is named

Promontorium Heraclides Promontorium Heraclides is a raised mountainous cape situated in Mare Imbrium on the near side of the Moon. Its selenographic coordinates are 40.3° N, 33.2° W and it is 50 km in diameter. It marks the western edge of the bay of Sinus Iridum ...

, while that at the northeast end is called

Promontorium Laplace Promontorium Laplace is a raised mountainous cape situated at the end of Montes Jura in Mare Imbrium on the near side of the Moon. Its selenographic coordinates are 46.8° N, 25.5° W and it is 2600 meters high. It forms the northeast boundary of ...

. This bay and the surrounding mountains is considered one of the most beautiful features on the Moon, and is a favorite among lunar observers. Sinus Iridum is formed from the remains of a large impact crater, which was subsequently flooded with basaltic lava, inundating the "sea" wall. The bay itself does not contain any notable impact craters, but does include the satellite crater Heraclides E in the south, Laplace A along the eastern edge, and Bianchini G in the north. The surface is level, but is marked by a number of

wrinkle ridge A wrinkle ridge is a type of feature commonly found on lunar maria, or basalt plains. These features are low, sinuous ridges formed on the mare surface that can extend for up to several hundred kilometers. Wrinkle ridges are tectonic features cr ...

s (dorsa). The

selenographic coordinates The selenographic coordinate system is used to refer to locations on the surface of Earth's moon. Any position on the lunar surface can be referenced by specifying two numerical values, which are comparable to the latitude and longitude of Earth. ...

of the bay's center are 45.01° N, 31.67° W, and the diameter is 249 km. It was the planned landing site of

Chang'e 3 Chang'e 3 (; ) is a robotic lunar exploration mission operated by the China National Space Administration (CNSA), incorporating a robotic lander and China's first lunar rover. It was launched in December 2013 as part of the second phase of ...

, China's 2013 lunar exploration mission, which instead landed nearby in

. When 10 to 11 days after

new moon In astronomy, the new moon is the first lunar phase, when the Moon and Sun have the same ecliptic longitude. At this phase, the lunar disk is not visible to the naked eye, except when it is silhouetted against the Sun during a solar eclipse. ...

the Sinus Iridium is still in shadow, the Montes Jura can already be visible at the

lunar terminator A terminator or twilight zone is a moving line that divides the daylit side and the dark night side of a planetary body. The terminator is defined as the locus of points on a planet or moon where the line through the center of its parent star is ...

. This geometry is also called

Golden Handle The Golden Handle is a visual effect at the Terminator (solar)#Lunar terminator, lunar terminator. About 10 to 11 days after new moon the valley of the rainbow bay (Sinus Iridum) is still in shadow, while the mountain peaks of the adjacent Montes ...

Satellite craters

By convention these features are identified on lunar maps by placing the letter on the side of the crater midpoint that is closest to Promontorium Heraclides. The following satellite craters are associated with the Promontorium Laplace.

References

External links

* , excellent earth-based image of Sinus Iridum and vicinity *
On the Shore of the Bay of Rainbows
-

Lunar Reconnaissance Orbiter The Lunar Reconnaissance Orbiter (LRO) is a NASA robotic spacecraft currently orbiting the Moon in an eccentric polar mapping orbit. Data collected by LRO have been described as essential for planning NASA's future human and robotic missions t ...

page with images
High resolution video
by Seán Doran of an overflight of Sinus Iridum, based on LRO data
this video
also passes over Sinus Iridum about halfway through (se
album
for more) {{DEFAULTSORT:Iridum, Sinus Maria on the Moon Mare Imbrium

Satellite craters

See also

References

External links