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Planetary Protection Policy
Planetary protection is a guiding principle in the design of an interplanetary mission, aiming to prevent biological contamination of both the target celestial body and the Earth (planet), Earth in the case of sample-return missions. Planetary protection reflects both the unknown nature of the space environment and the desire of the scientific community to preserve the pristine nature of celestial bodies until they can be studied in detail. There are two types of interplanetary contamination. Forward contamination is the transfer of Natural selection#Types of selection, viable organisms from Earth to another celestial body. Back contamination is the transfer of potential Extraterrestrial life, extraterrestrial organisms back to the Earth's biosphere. History The potential problem of lunar and planetary contamination was first raised at the International Astronautical Federation VIIth Congress in Rome in 1956. In 1958 the U.S. National Academy of Sciences (NAS) passed a resolu ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Viking Oven
Vikings were seafaring people originally from Scandinavia (present-day Denmark, Norway, and Sweden), who from the late 8th to the late 11th centuries raided, pirated, traded, and settled throughout parts of Europe.Roesdahl, pp. 9–22. They also voyaged as far as the Mediterranean Sea, Mediterranean, North Africa, the Middle East, Greenland, and Vinland (present-day Newfoundland in Canada, North America). In their countries of origin, and some of the countries they raided and settled in, this period is popularly known as the Viking Age, and the term "Viking" also commonly includes the inhabitants of the Scandinavian homelands as a whole. The Vikings had a profound impact on the Early Middle Ages, early medieval history of Northern Europe, northern and Eastern Europe, including the political and social development of England (and the English language) and parts of France, and established the embryo of Russia in Kievan Rus'. Expert sailors and navigators of their cha ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
History
History is the systematic study of the past, focusing primarily on the Human history, human past. As an academic discipline, it analyses and interprets evidence to construct narratives about what happened and explain why it happened. Some theorists categorize history as a social science, while others see it as part of the humanities or consider it a hybrid discipline. Similar debates surround the purpose of history—for example, whether its main aim is theoretical, to uncover the truth, or practical, to learn lessons from the past. In a more general sense, the term ''history'' refers not to an academic field but to the past itself, times in the past, or to individual texts about the past. Historical research relies on Primary source, primary and secondary sources to reconstruct past events and validate interpretations. Source criticism is used to evaluate these sources, assessing their authenticity, content, and reliability. Historians strive to integrate the perspectives o ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Titan (moon)
Titan is the largest moon of Saturn and the List of Solar System objects by size, second-largest in the Solar System. It is the only Natural satellite, moon known to have an atmosphere denser than the Atmosphere of Earth, Earth's and is the only known object in space—other than Earth—on which there is clear evidence that stable bodies of liquid exist. Titan is one of seven List of gravitationally rounded objects of the Solar System, gravitationally rounded moons of Saturn and the second-most distant among them. Frequently described as a Planetary-mass moon, planet-like moon, Titan is 50% larger in diameter than Earth's Moon and 80% more Mass, massive. It is the second-largest moon in the Solar System after Jupiter's Ganymede (moon), Ganymede and is larger than Mercury (planet), Mercury; yet Titan is only 40% as massive as Mercury, because Mercury is mainly iron and rock while much of Titan is ice, which is less dense. Discovered in 1655 by the Dutch astronomer Christiaan ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Hard Landing
A hard landing occurs when an aircraft or spacecraft hits the ground with a greater vertical speed and force than in a normal landing. The terms ''hard landing'' and ''firm landing'' are often confused though are inherently different. A hard landing is never intended and if an aircraft has had a hard landing, it must be inspected for damage before its next flight. In contrast, depending on aircraft type (e.g. Boeing 737) and/or environmental conditions (e.g. gusty or crosswind conditions, wet runway, etc.) a firm landing is intended and even demanded by the aircraft manual. Landing is the final phase in flight, in which the aircraft returns to the ground. The average vertical speed in a landing is around ; any greater vertical speed should be classed by crew as ''hard''. Crew judgment is most reliable to determine hard landing, as determination based on recorded acceleration value is difficult and not advisable, partially because there is no recording of true vertical accelera ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Containment And Quarantine For Restricted Category V Sample Return
Containment was a geopolitical strategic foreign policy pursued by the United States during the Cold War to prevent the spread of communism after the end of World War II. The name was loosely related to the term '' cordon sanitaire'', which was containment of the Soviet Union in the interwar period. Containment represented a middle-ground position between détente (relaxation of relations) and rollback (actively replacing a regime). The basis of the doctrine was articulated in a 1946 cable by U.S. diplomat George F. Kennan during the post-World War II term of U.S. President Harry S. Truman. As a description of U.S. foreign policy, the word originated in a report Kennan submitted to US Defense Secretary James Forrestal in 1947, which was later used in a ''Foreign Affairs'' article. In a broader context, the term is employed to denote a strategy designed to limit or hinder an opponent's capacity for international power projection. China used this term to characterize the Un ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Bacillus
''Bacillus'', from Latin "bacillus", meaning "little staff, wand", is a genus of Gram-positive, rod-shaped bacteria, a member of the phylum ''Bacillota'', with 266 named species. The term is also used to describe the shape (rod) of other so-shaped bacteria; and the plural ''Bacilli'' is the name of the class of bacteria to which this genus belongs. ''Bacillus'' species can be either obligate aerobes which are dependent on oxygen, or facultative anaerobes which can survive in the absence of oxygen. Cultured ''Bacillus'' species test positive for the enzyme catalase if oxygen has been used or is present. ''Bacillus'' can reduce themselves to oval endospores and can remain in this dormant state for years. The endospore of one species from Morocco is reported to have survived being heated to 420 °C. Endospore formation is usually triggered by a lack of nutrients: the bacterium divides within its cell wall, and one side then engulfs the other. They are not true spores (i.e. ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Planetary Protection
Planetary protection is a guiding principle in the design of an interplanetary mission, aiming to prevent biological contamination of both the target celestial body and the Earth in the case of sample-return missions. Planetary protection reflects both the unknown nature of the space environment and the desire of the scientific community to preserve the pristine nature of celestial bodies until they can be studied in detail. There are two types of interplanetary contamination. Forward contamination is the transfer of viable organisms from Earth to another celestial body. Back contamination is the transfer of potential extraterrestrial organisms back to the Earth's biosphere. History The potential problem of lunar and planetary contamination was first raised at the International Astronautical Federation VIIth Congress in Rome in 1956. In 1958 the U.S. National Academy of Sciences (NAS) passed a resolution stating, “The National Academy of Sciences of the United States of A ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Enceladus (moon)
Enceladus is the sixth-largest moon of Saturn and the 18th-largest in the Solar System. It is about in diameter, about a tenth of that of Saturn's largest moon, Titan (moon), Titan. It is covered by clean, freshly deposited snow hundreds of meters thick, making it one of the most reflective bodies of the Solar System. Consequently, its surface temperature at noon reaches only , far colder than a light-absorbing body would be. Despite its small size, Enceladus has a wide variety of surface features, ranging from old, heavily impact crater, cratered regions to young, Tectonics, tectonically deformed terrain. Enceladus was discovered on August 28, 1789, by William Herschel, but little was known about it until the two Voyager program, Voyager spacecraft, ''Voyager 1'' and ''Voyager 2'', flew by Saturn in 1980 and 1981. In 2005, the spacecraft ''Cassini–Huygens, Cassini'' started multiple close flybys of Enceladus, revealing its surface and environment in greater detail ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Europa (moon)
Europa () is a moons of Jupiter, natural satellite (moon) of Jupiter. Being observable from Earth with common binoculars it is one of the four Galilean moons. As such it is a planetary-mass moon, the smallest and least massive orbiting Jupiter, and slightly smaller and less massive than Moon, Earth's. Europa is an icy moon, being of the three icy Galilean moons the closest orbiting Jupiter. As a result it is exhibiting a relatively young surface, driven by tidal heating. Probably having an iron–nickel alloy, iron–nickel core, it consists mainly of silicate rock, with a water-ice shell. It has a very thin atmosphere, composed primarily of oxygen. Its geologically young white-beige surface is Glacial striation, striated by light Tan (color), tan cracks and streaks, with very few impact craters. In addition to Earth-bound telescope observations, Europa has been examined by a succession of space-probe flybys, the first occurring in the early 1970s. In September 2022, the Juno ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Mars
Mars is the fourth planet from the Sun. It is also known as the "Red Planet", because of its orange-red appearance. Mars is a desert-like rocky planet with a tenuous carbon dioxide () atmosphere. At the average surface level the atmospheric pressure is a few thousandths of Earth's, atmospheric temperature ranges from and cosmic radiation is high. Mars retains some water, in the ground as well as thinly in the atmosphere, forming cirrus clouds, frost, larger polar regions of permafrost and ice caps (with seasonal snow), but no liquid surface water. Its surface gravity is roughly a third of Earth's or double that of the Moon. It is half as wide as Earth or twice the Moon, with a diameter of , and has a surface area the size of all the dry land of Earth. Fine dust is prevalent across the surface and the atmosphere, being picked up and spread at the low Martian gravity even by the weak wind of the tenuous atmosphere. The terrain of Mars roughly follows a north-south ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Comet
A comet is an icy, small Solar System body that warms and begins to release gases when passing close to the Sun, a process called outgassing. This produces an extended, gravitationally unbound atmosphere or Coma (cometary), coma surrounding the nucleus, and sometimes a Comet tail, tail of gas and dust gas blown out from the coma. These phenomena are due to the effects of solar radiation and the outstreaming solar wind plasma acting upon the nucleus of the comet. Comet nuclei range from a few hundred meters to tens of kilometers across and are composed of loose collections of ice, dust, and small rocky particles. The coma may be up to 15 times Earth's diameter, while the tail may stretch beyond one astronomical unit. If sufficiently close and bright, a comet may be seen from Earth without the aid of a telescope and can Subtended angle, subtend an arc of up to 30° (60 Moons) across the sky. Comets have been observed and recorded since ancient times by many cultures and religion ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Venus
Venus is the second planet from the Sun. It is often called Earth's "twin" or "sister" planet for having almost the same size and mass, and the closest orbit to Earth's. While both are rocky planets, Venus has an atmosphere much thicker and denser than Earth and any other rocky body in the Solar System. Its atmosphere is composed of mostly carbon dioxide (), with a global sulfuric acid cloud cover and no liquid water. At the mean surface level the atmosphere reaches a temperature of and a pressure 92 times greater than Earth's at sea level, turning the lowest layer of the atmosphere into a supercritical fluid. Venus is the third brightest object in Earth's sky, after the Moon and the Sun, and, like Mercury, appears always relatively close to the Sun, either as a "morning star" or an "evening star", resulting from orbiting closer ( inferior) to the Sun than Earth. The orbits of Venus and Earth make the two planets approach each other in synodic periods of 1.6 years ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
