Moore, P., Ann. Google Scholar. Quasi-satellites are asteroids that exhibit a 1:1 orbital resonance with a host planet. Get the most important science stories of the day, free in your inbox. Then, over a period lasting until perhaps three billion years ago, a long sequence of volcanic events flooded the giant basins and surrounding low-lying areas with magma originating hundreds of kilometres within the interior. The highlands formed very early while the Moon’s surface was molten. To obtain Then, the less dense minerals such as anorthositic plagioclase feldspar crystallized and floated to the magma surface forming an anorthosite crust. Samples of lunar rock and soil brought back by Apollo astronauts proved that the maria are composed of basalt formed from surface lava flows that later congealed. Nature The lunar maria are covered with basalt lava flows. The densest minerals such as iron and magnesium silicates crystallized and sank after the cooling of the magma ocean. The image shows the two major environmental features of the lunar surface, the bright and heavily cratered highlands (or terrae) and the smooth dark maria. Internet Explorer). (Together with the bright lunar highlands, they form the face of the “man in the moon.”). I have discussed this matter elsewhere3,4. In the meantime, to ensure continued support, we are displaying the site without styles Share it with your friends! Before the first unmanned spacecraft landings on the Moon in the 1960s, some astronomers feared that the surface would be so pulverized that the machines might sink in. For instance, most lunar mare has not been sampled and data for these mare basalts are derived only by remote sensing, impact crater counts, and crater degradation. Article Particularly important, however, is the conclusion that the well-formed maria fit in to the general pattern; it is difficult to avoid the conclusion that, for example, the Mare Crisium is simply a large member of the Vendelinus chain. The acquired knowledge can be extended to develop evolutive models for distant moons and planets. The lunar maria are dark spots on the Moon. Most of the maria are associated with mascons, regions of particularly dense lava that create anomalies in the Moon’s gravitational field. Is There a Ninth Planet in the Solar System? Studies of ages and chemical composition of the basaltic lunar maria may provide clues on the Moon’s internal formation and evolution. There are significant, well-marked chains approximately aligned with the central meridian as seen from Earth; in the west (classical sense) the chain to which Vendelinus and Langrenus belong; near the centre, the Walter and the Ptolemaeus chains; in the east, the Grimaldi chain, and so on. Maria are the largest topographic features on the Moon and can be seen from Earth with the unaided eye. This was well after the lunar crust had cooled and solidified enough, following the Moon’s formation, to retain large impact scars. Since, these plains are darker than the bright highlands the early observers interpreted them as water seas. Our editors will review what you’ve submitted and determine whether to revise the article. Be on the lookout for your Britannica newsletter to get trusted stories delivered right to your inbox. THE hypothesis proposed by Kopal1 concerning the origin of the lunar maria is very interesting. Let us know if you have suggestions to improve this article (requires login). In actuality, maria are huge basins containing lava flows marked by craters, ridges, faults, and straight and meandering valleys called rilles and are devoid of water. and JavaScript. However, it is important to note that the distribution of lunar craters on the Earth-turned hemisphere is far from uniform. Although the recognized giant impact basins are distributed similarly on the near and far sides of the Moon, most of the far-side basins were never flooded with lava to form maria. The maria basins were formed beginning about 3.9 billion years ago during a period of intense bombardment by asteroid-sized bodies. We suggest that quasi-satellites of Earth may be responsible for lunar maria causing impacts. Nature 210, 1347 (1966). In addition, geologic maps may be used in the preparation of future missions. ADS Our latest podcast episode features popular TED speaker Mara Mintzer. If you find something abusive or that does not comply with our terms or guidelines please flag it as inappropriate. Studies of ages and chemical composition of the basaltic lunar maria may provide clues on the Moon’s internal formation … The reason remains to be clarified, but it may be related to an asymmetry of the Moon’s crust, which appears to be about twice as thick on the far side as on the near side and thus less likely to have been completely ruptured by large impacts. A satisfactory theory for the origin of maria must provide a genetic link between the origin of the depression and the origin of the material which floors it. For instance, most lunar mare has not been sampled and data for these mare basalts are derived only by remote sensing, impact crater counts, and crater degradation. Omissions? Corrections? The suggestion by Baldwin2, according to which the alignments are not real and are due to lighting effects, does not fit the facts. The lunar maria have aroused the curiosity of people of different places and cultures along the time. 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The oldest ages for returned lunar mare basalts are from Apollo 14 breccias; aluminous low-Ti basaltic clasts in these breccias range in age from 3.9 to 4.3 billion years. Astronomer Denilso Camargo on the Moon formation and the major environmental features of the lunar surface. Astrophysicist Christopher McKee on the birth of stars, ways to determine the mass of a primordial star, and the emergence of supernovas and black holes, MIT Professor Seth Lloyd on the origin of life, the butterfly effect, and the Universe as a quantum computer. These are the Moon’s maria or, in the singular, lunar mare (Latin word for sea), which cover about 17% of the lunar crust. Lunar maria is simply hot lava that spewed over the moon’s surface, and eventually melted shapes into the crust, and over time hardened into rocks which were found to be very similar to basalt. From the point of view of science, lunar samples from Appolo and Luna missions provide important, but insufficient data to disentangle the thermal history and evolution of the Moon. These lunar basalts have a mineralogy similar to that of terrestrial basalts, but chemically they have no water, a lower amount of alkalis and alumina, and a higher iron oxide and chromium content. In the early phase of the Moon formation its outer layers, heated by the kinetic energy of impacting bodies and the decay of radioactive elements, were molten forming a global magma ocean. Moore, P., Survey of the Moon (Eyre and Spottiswoode, London, 1963). https://doi.org/10.1038/2101347a0. The familiar near side of Earth's Moon, photographed on December 7, 1992, by the Galileo spacecraft on its way to Jupiter. Did you like it? Nature By signing up for this email, you are agreeing to news, offers, and information from Encyclopaedia Britannica. PubMed Google Scholar, MOORE, P. Origin of the Lunar Maria. These missions—and the manned landings that followed—revealed that the regolith was only somewhat compressible and was firm enough to be supportive. However, craters may be degraded by the cumulative effects of small impacts. Mare, plural maria, any flat, dark plain of lower elevation on the Moon. This was well after the lunar crust had cooled and solidified enough, following the Moon’s formation, to retain large impact scars. Sign up for the Nature Briefing newsletter — what matters in science, free to your inbox daily. Two primary kinds of terrain are visible—the lighter areas, which constitute the heavily cratered and very old highlands, and the darker, roughly circular plains, traditionally called maria, which are relatively young lava-filled impact basins.Among the maria are (left to right) the crescent-shaped Oceanus Procellarum near the left limb, the large, almost perfectly circular Mare Imbrium, or Imbrium Basin (with the crater Copernicus a bright dot at its lower margin), Mare Serenitatis immediately to the right of Imbrium, Mare Tranquillitatis to the lower right of Serenitatis, and Mare Crisium, isolated near the right limb. The surface, down to approximately 5 metres (16 feet), shows effects of churning, fusing, and fragmenting as a result of several billion years of bombardment by small meteoroids. Currently the evolution of the lunar landscape is dominated by the occasional impact craters, since in the absence of an atmosphere there is no erosive agents such as winds and rain. THE hypothesis proposed by Kopal1 concerning the origin of the lunar maria is very interesting. There are about 20 major areas of this type, most of them—including the largest ones—located on the side of the Moon that always faces Earth. N.Y. Acad. (Inong, Freedman 10) Tags: Facts lunar Maria topography. The maria basins were formed beginning about 3.9 billion years ago during a period of intense bombardment by asteroid-sized bodies. Another bright crater, Tycho, stands out at the bottom left of the image. The oldest basalt from a visible maria is Apollo sample number 10003, a low-K basalt from Mare Tranquilitatis with an age of 3.86 ± 0.03 billion years. Google Scholar. The Planetarium, Armagh, Northern Ireland, You can also search for this author in You are using a browser version with limited support for CSS. Lunar maria are not simply large lunar craters. The term, which in Latin means “sea,” was erroneously applied to such features by telescopic observers of the 17th century. Anorthosite is the most abundant and oldest rock on the lunar crust. The man in the Moon, the Moon rabbit, and Saint George killing the dragon are examples of lunar pareidolia. Most craters have raised rims; most maria are bordered partly or wholly by broad zones of downwarping. This debris layer, comprising rock fragments of all sizes down to fine dust, is called regolith. Article The lunar maria were formed between 3.16 and 4.2 billion years ago, as measured by radiometric dating, though crater counting methods suggest that some portions may have formed as recently as 1.2 billion years ago. Updates? Lunar basalts are less porous than the anorthosites, so highland’s craters are generally deeper than maria’s ones. Thank you for visiting nature.com.
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