Category Archives: Transhuman News

Second largest Galilean moon of Jupiter and third largest in the solar system

Callisto , or Jupiter IV, is the second-largest moon of Jupiter, after Ganymede. It is the third-largest moon in the Solar System after Ganymede and Saturn's largest moon Titan, and the largest object in the Solar System that may not be properly differentiated. Callisto was discovered in 1610 by Galileo Galilei. At 4821km in diameter , Callisto has about 99% the diameter of the planet Mercury but only about a third of its mass. It is the fourth Galilean moon of Jupiter by distance, with an orbital radius of about 1883000km.[3] It is not in an orbital resonance like the three other Galilean satellitesIo, Europa, and Ganymedeand is thus not appreciably tidally heated.[10] Callisto's rotation is tidally locked to its orbit around Jupiter, so that the same hemisphere always faces inward. Because of this, there is a sub-Jovian point on Callisto's surface, from which Jupiter would appear to hang directly overhead. It is less affected by Jupiter's magnetosphere than the other inner satellites because of its more remote orbit, located just outside Jupiter's main radiation belt.[11][12]

Callisto is composed of approximately equal amounts of rock and ices, with a density of about 1.83g/cm3, the lowest density and surface gravity of Jupiter's major moons. Compounds detected spectroscopically on the surface include water ice,[13] carbon dioxide, silicates, and organic compounds. Investigation by the Galileo spacecraft revealed that Callisto may have a small silicate core and possibly a subsurface ocean of liquid water[13] at depths greater than 100km.[14][15]

The surface of Callisto is the oldest and most heavily cratered in the Solar System.[16] Its surface is completely covered with impact craters.[17] It does not show any signatures of subsurface processes such as plate tectonics or volcanism, with no signs that geological activity in general has ever occurred, and is thought to have evolved predominantly under the influence of impacts.[18] Prominent surface features include multi-ring structures, variously shaped impact craters, and chains of craters (catenae) and associated scarps, ridges and deposits.[18] At a small scale, the surface is varied and made up of small, sparkly frost deposits at the tips of high spots, surrounded by a low-lying, smooth blanket of dark material.[6] This is thought to result from the sublimation-driven degradation of small landforms, which is supported by the general deficit of small impact craters and the presence of numerous small knobs, considered to be their remnants.[19] The absolute ages of the landforms are not known.

Callisto is surrounded by an extremely thin atmosphere composed of carbon dioxide[8] and probably molecular oxygen,[9] as well as by a rather intense ionosphere.[20] Callisto is thought to have formed by slow accretion from the disk of the gas and dust that surrounded Jupiter after its formation.[21] Callisto's gradual accretion and the lack of tidal heating meant that not enough heat was available for rapid differentiation. The slow convection in the interior of Callisto, which commenced soon after formation, led to partial differentiation and possibly to the formation of a subsurface ocean at a depth of 100150km and a small, rocky core.[22]

The likely presence of an ocean within Callisto leaves open the possibility that it could harbor life. However, conditions are thought to be less favorable than on nearby Europa.[23] Various space probes from Pioneers 10 and 11 to Galileo and Cassini have studied Callisto. Because of its low radiation levels, Callisto has long been considered the most suitable place for a human base for future exploration of the Jovian system.[24]

Callisto was discovered by Galileo in January 1610, along with the three other large Jovian moonsGanymede, Io, and Europa.[1]

Callisto is named after one of Zeus's many lovers or other sexual partners in Greek mythology. Callisto was a nymph (or, according to some sources, the daughter of Lycaon) who was associated with the goddess of the hunt, Artemis.[25] The name was suggested by Simon Marius soon after Callisto's discovery.[26] Marius attributed the suggestion to Johannes Kepler.[25]

... autem celebrantur tres fmin Virgines, quarum furtivo amore Iupiter captus & positus est... Calisto Lycaonis... filia... me vocatur... Quartus denique Calisto... [Io,] Europa, Ganimedes puer, atque Calisto, lascivo nimium perplacuere Jovi.

... three young women who were captured by Jupiter for secret love shall be honoured, [including] Callisto, the daughter of Lycaon... Finally, the fourth [moon] is called by me Callisto... Io, Europa, the boy Ganymede, and Callisto greatly pleased lustful Jupiter.[27]

However, the names of the Galilean satellites fell into disfavor for a considerable time, and were not revived in common use until the mid-20th century. In much of the earlier astronomical literature, Callisto is referred to by its Roman numeral designation, a system introduced by Galileo, as Jupiter IV or as "the fourth satellite of Jupiter".[28]

There's no established English adjectival form of the name. The adjectival form of Greek Kallisti is Kallisti-os, from which one might expect Latin Callistius and English *Callistian, parallel to Sapphian for Sapphi[29] and Letian for Lti.[30] However, the iota subscript is often omitted from such Greek names (cf. Inan[31] from ni[32] and Argan[33] from Argi[34]), and indeed the analogous form Callistoan is found.[35][36][37]In Virgil, a second oblique stem appears in Latin: Callistn-,[38] but the corresponding Callistonian has rarely appeared in English.[39] One also sees ad hoc forms, such as Callistan,[19] Callistian[40] and Callistean.[41][42]

Callisto is the outermost of the four Galilean moons of Jupiter. It orbits at a distance of approximately 1880000km (26.3 times the 71492km radius of Jupiter itself).[3] This is significantly larger than the orbital radius1070000kmof the next-closest Galilean satellite, Ganymede. As a result of this relatively distant orbit, Callisto does not participate in the mean-motion resonancein which the three inner Galilean satellites are lockedand probably never has.[10]

Like most other regular planetary moons, Callisto's rotation is locked to be synchronous with its orbit.[4] The length of Callisto's day, simultaneously its orbital period, is about 16.7 Earth days. Its orbit is very slightly eccentric and inclined to the Jovian equator, with the eccentricity and inclination changing quasi-periodically due to solar and planetary gravitational perturbations on a timescale of centuries. The ranges of change are 0.00720.0076 and 0.200.60, respectively.[10] These orbital variations cause the axial tilt (the angle between rotational and orbital axes) to vary between 0.4 and 1.6.[43]

The dynamical isolation of Callisto means that it has never been appreciably tidally heated, which has important consequences for its internal structure and evolution.[44] Its distance from Jupiter also means that the charged-particle flux from Jupiter's magnetosphere at its surface is relatively lowabout 300 times lower than, for example, that at Europa. Hence, unlike the other Galilean moons, charged-particle irradiation has had a relatively minor effect on Callisto's surface.[11] The radiation level at Callisto's surface is equivalent to a dose of about 0.01 rem (0.1 mSv) per day, which is over ten times higher than Earth's average background radiation.[45][46]

The average density of Callisto, 1.83g/cm3,[4] suggests a composition of approximately equal parts of rocky material and water ice, with some additional volatile ices such as ammonia.[14] The mass fraction of ices is 4955%.[14][22] The exact composition of Callisto's rock component is not known, but is probably close to the composition of L/LL type ordinary chondrites,[14] which are characterized by less total iron, less metallic iron and more iron oxide than H chondrites. The weight ratio of iron to silicon is 0.91.3 in Callisto, whereas the solar ratio is around 1:8.[14]

Callisto's surface has an albedo of about 20%.[6] Its surface composition is thought to be broadly similar to its composition as a whole. Near-infrared spectroscopy has revealed the presence of water ice absorption bands at wavelengths of 1.04, 1.25, 1.5, 2.0 and 3.0 micrometers.[6] Water ice seems to be ubiquitous on the surface of Callisto, with a mass fraction of 2550%.[15] The analysis of high-resolution, near-infrared and UV spectra obtained by the Galileo spacecraft and from the ground has revealed various non-ice materials: magnesium- and iron-bearing hydrated silicates,[6] carbon dioxide,[48] sulfur dioxide,[49] and possibly ammonia and various organic compounds.[15][6] Spectral data indicate that Callisto's surface is extremely heterogeneous at the small scale. Small, bright patches of pure water ice are intermixed with patches of a rockice mixture and extended dark areas made of a non-ice material.[6][18]

The Callistoan surface is asymmetric: the leading hemisphere is darker than the trailing one. This is different from other Galilean satellites, where the reverse is true.[6] The trailing hemisphere of Callisto appears to be enriched in carbon dioxide, whereas the leading hemisphere has more sulfur dioxide.[50] Many fresh impact craters like Lofn also show enrichment in carbon dioxide.[50] Overall, the chemical composition of the surface, especially in the dark areas, may be close to that seen on D-type asteroids,[18] whose surfaces are made of carbonaceous material.

Callisto's battered surface lies on top of a cold, stiff, and icy lithosphere that is between 80 and 150km thick.[14][22] A salty ocean 150200km deep may lie beneath the crust,[14][22] indicated by studies of the magnetic fields around Jupiter and its moons.[51][52] It was found that Callisto responds to Jupiter's varying background magnetic field like a perfectly conducting sphere; that is, the field cannot penetrate inside Callisto, suggesting a layer of highly conductive fluid within it with a thickness of at least 10km.[52] The existence of an ocean is more likely if water contains a small amount of ammonia or other antifreeze, up to 5% by weight.[22] In this case the water+ice layer can be as thick as 250300km.[14] Failing an ocean, the icy lithosphere may be somewhat thicker, up to about 300km.

Beneath the lithosphere and putative ocean, Callisto's interior appears to be neither entirely uniform nor particularly variable. Galileo orbiter data[4] (especially the dimensionless moment of inertia[h]0.35490.0042determined during close flybys) suggest that, if Callisto is in hydrostatic equilibrium, its interior is composed of compressed rocks and ices, with the amount of rock increasing with depth due to partial settling of its constituents.[14][53] In other words, Callisto may be only partially differentiated. The density and moment of inertia for an equilibrium Callisto are compatible with the existence of a small silicate core in the center of Callisto. The radius of any such core cannot exceed 600km, and the density may lie between 3.1 and 3.6g/cm3.[4][14] In this case, Callisto's interior would be in stark contrast to that of Ganymede, which appears to be fully differentiated.[15][54]

However, a 2011 reanalysis of Galileo data suggests that Callisto is not in hydrostatic equilibrium; its S22 coefficient from gravity data is an anomalous 10% of its C22 value, which is not consistent with a body in hydrostatic equilibrium and thus significantly increases the error bars on Callisto's moment of inertia. Further, an undifferentiated Callisto is inconsistent with the presence of a substantial internal ocean as inferred by magnetic data, and it would be difficult for an object as large as Callisto to fail to differentiate at any point.[55] In that case, the gravity data may be more consistent with a more thoroughly differentiated Callisto with a hydrated silicate core.[56]

The ancient surface of Callisto is one of the most heavily cratered in the Solar System.[57] In fact, the crater density is close to saturation: any new crater will tend to erase an older one. The large-scale geology is relatively simple; there are no large mountains on Callisto, volcanoes or other endogenic tectonic features.[58] The impact craters and multi-ring structurestogether with associated fractures, scarps and depositsare the only large features to be found on the surface.[18][58]

Callisto's surface can be divided into several geologically different parts: cratered plains, light plains, bright and dark smooth plains, and various units associated with particular multi-ring structures and impact craters.[18][58] The cratered plains constitute most of the surface area and represent the ancient lithosphere, a mixture of ice and rocky material. The light plains include bright impact craters like Burr and Lofn, as well as the effaced remnants of old large craters called palimpsests,[i] the central parts of multi-ring structures, and isolated patches in the cratered plains.[18] These light plains are thought to be icy impact deposits. The bright, smooth plains constitute a small fraction of Callisto's surface and are found in the ridge and trough zones of the Valhalla and Asgard formations and as isolated spots in the cratered plains. They were thought to be connected with endogenic activity, but the high-resolution Galileo images showed that the bright, smooth plains correlate with heavily fractured and knobby terrain and do not show any signs of resurfacing.[18] The Galileo images also revealed small, dark, smooth areas with overall coverage less than 10,000km2, which appear to embay[j] the surrounding terrain. They are possible cryovolcanic deposits.[18] Both the light and the various smooth plains are somewhat younger and less cratered than the background cratered plains.[18][59]

Impact crater diameters seen range from 0.1kma limit defined by the imaging resolutionto over 100km, not counting the multi-ring structures.[18] Small craters, with diameters less than 5km, have simple bowl or flat-floored shapes. Those 540km across usually have a central peak. Larger impact features, with diameters in the range 25100km, have central pits instead of peaks, such as Tindr crater.[18] The largest craters with diameters over 60km can have central domes, which are thought to result from central tectonic uplift after an impact;[18] examples include Doh and Hr craters. A small number of very largemore than 100km in diameterand bright impact craters show anomalous dome geometry. These are unusually shallow and may be a transitional landform to the multi-ring structures, as with the Lofn impact feature.[18] Callisto's craters are generally shallower than those on the Moon.

The largest impact features on Callisto's surface are multi-ring basins.[18][58] Two are enormous. Valhalla is the largest, with a bright central region 600kilometers in diameter, and rings extending as far as 1,800kilometers from the center (see figure).[60] The second largest is Asgard, measuring about 1,600kilometers in diameter.[60] Multi-ring structures probably originated as a result of a post-impact concentric fracturing of the lithosphere lying on a layer of soft or liquid material, possibly an ocean.[35] The catenaefor example Gomul Catenaare long chains of impact craters lined up in straight lines across the surface. They were probably created by objects that were tidally disrupted as they passed close to Jupiter prior to the impact on Callisto, or by very oblique impacts.[18] A historical example of a disruption was Comet Shoemaker-Levy 9.

As mentioned above, small patches of pure water ice with an albedo as high as 80% are found on the surface of Callisto, surrounded by much darker material.[6] High-resolution Galileo images showed the bright patches to be predominately located on elevated surface features: crater rims, scarps, ridges and knobs.[6] They are likely to be thin water frost deposits. Dark material usually lies in the lowlands surrounding and mantling bright features and appears to be smooth. It often forms patches up to 5km across within the crater floors and in the intercrater depressions.[6]

On a sub-kilometer scale the surface of Callisto is more degraded than the surfaces of other icy Galilean moons.[6] Typically there is a deficit of small impact craters with diameters less than 1km as compared with, for instance, the dark plains on Ganymede.[18] Instead of small craters, the almost ubiquitous surface features are small knobs and pits.[6] The knobs are thought to represent remnants of crater rims degraded by an as-yet uncertain process.[19] The most likely candidate process is the slow sublimation of ice, which is enabled by a temperature of up to 165K, reached at a subsolar point.[6] Such sublimation of water or other volatiles from the dirty ice that is the bedrock causes its decomposition. The non-ice remnants form debris avalanches descending from the slopes of the crater walls.[19] Such avalanches are often observed near and inside impact craters and termed "debris aprons".[6][18][19] Sometimes crater walls are cut by sinuous valley-like incisions called "gullies", which resemble certain Martian surface features.[6] In the ice sublimation hypothesis, the low-lying dark material is interpreted as a blanket of primarily non-ice debris, which originated from the degraded rims of craters and has covered a predominantly icy bedrock.

The relative ages of the different surface units on Callisto can be determined from the density of impact craters on them. The older the surface, the denser the crater population.[61] Absolute dating has not been carried out, but based on theoretical considerations, the cratered plains are thought to be ~4.5billion years old, dating back almost to the formation of the Solar System. The ages of multi-ring structures and impact craters depend on chosen background cratering rates and are estimated by different authors to vary between 1 and 4billion years.[18][57]

Callisto has a very tenuous atmosphere composed of carbon dioxide.[8] It was detected by the Galileo Near Infrared Mapping Spectrometer (NIMS) from its absorption feature near the wavelength 4.2micrometers. The surface pressure is estimated to be 7.5 picobar (0.75 Pa) and particle density 4108cm3. Because such a thin atmosphere would be lost in only about 4days (see atmospheric escape), it must be constantly replenished, possibly by slow sublimation of carbon dioxide ice from Callisto's icy crust,[8] which would be compatible with the sublimationdegradation hypothesis for the formation of the surface knobs.

Callisto's ionosphere was first detected during Galileo flybys;[20] its high electron density of 717104cm3 cannot be explained by the photoionization of the atmospheric carbon dioxide alone. Hence, it is suspected that the atmosphere of Callisto is actually dominated by molecular oxygen (in amounts 10100 times greater than CO2).[9] However, oxygen has not yet been directly detected in the atmosphere of Callisto. Observations with the Hubble Space Telescope (HST) placed an upper limit on its possible concentration in the atmosphere, based on lack of detection, which is still compatible with the ionospheric measurements.[62] At the same time, HST was able to detect condensed oxygen trapped on the surface of Callisto.[63]

Atomic hydrogen has also been detected in Callisto's atmosphere via recent analysis of 2001 Hubble Space Telescope data.[64] Spectral images taken on 15 and 24 December 2001 were re-examined, revealing a faint signal of scattered light that indicates a hydrogen corona. The observed brightness from the scattered sunlight in Callisto's hydrogen corona is approximately two times larger when the leading hemisphere is observed. This asymmetry may originate from a different hydrogen abundance in both leading and trailing hemispheres. However, this hemispheric difference in Callisto's hydrogen corona brightness is likely to originate from the extinction of the signal in the Earth's geocorona, which is greater when the trailing hemisphere is observed.[65]

The partial differentiation of Callisto (inferred e.g. from moment of inertia measurements) means that it has never been heated enough to melt its ice component.[22] Therefore, the most favorable model of its formation is a slow accretion in the low-density Jovian subnebulaa disk of the gas and dust that existed around Jupiter after its formation.[21] Such a prolonged accretion stage would allow cooling to largely keep up with the heat accumulation caused by impacts, radioactive decay and contraction, thereby preventing melting and fast differentiation.[21] The allowable timescale of formation of Callisto lies then in the range 0.1million10million years.[21]

The further evolution of Callisto after accretion was determined by the balance of the radioactive heating, cooling through thermal conduction near the surface, and solid state or subsolidus convection in the interior.[44] Details of the subsolidus convection in the ice is the main source of uncertainty in the models of all icy moons. It is known to develop when the temperature is sufficiently close to the melting point, due to the temperature dependence of ice viscosity.[66] Subsolidus convection in icy bodies is a slow process with ice motions of the order of 1centimeter per year, but is, in fact, a very effective cooling mechanism on long timescales.[66] It is thought to proceed in the so-called stagnant lid regime, where a stiff, cold outer layer of Callisto conducts heat without convection, whereas the ice beneath it convects in the subsolidus regime.[22][66] For Callisto, the outer conductive layer corresponds to the cold and rigid lithosphere with a thickness of about 100km. Its presence would explain the lack of any signs of the endogenic activity on the Callistoan surface.[66][67] The convection in the interior parts of Callisto may be layered, because under the high pressures found there, water ice exists in different crystalline phases beginning from the ice I on the surface to ice VII in the center.[44] The early onset of subsolidus convection in the Callistoan interior could have prevented large-scale ice melting and any resulting differentiation that would have otherwise formed a large rocky core and icy mantle. Due to the convection process, however, very slow and partial separation and differentiation of rocks and ices inside Callisto has been proceeding on timescales of billions of years and may be continuing to this day.[67]

The current understanding of the evolution of Callisto allows for the existence of a layer or "ocean" of liquid water in its interior. This is connected with the anomalous behavior of ice I phase's melting temperature, which decreases with pressure, achieving temperatures as low as 251K at 2,070bar (207MPa).[22] In all realistic models of Callisto the temperature in the layer between 100 and 200km in depth is very close to, or exceeds slightly, this anomalous melting temperature.[44][66][67] The presence of even small amounts of ammoniaabout 12% by weightalmost guarantees the liquid's existence because ammonia would lower the melting temperature even further.[22]

Although Callisto is very similar in bulk properties to Ganymede, it apparently had a much simpler geological history. The surface appears to have been shaped mainly by impacts and other exogenic forces.[18] Unlike neighboring Ganymede with its grooved terrain, there is little evidence of tectonic activity.[15] Explanations that have been proposed for the contrasts in internal heating and consequent differentiation and geologic activity between Callisto and Ganymede include differences in formation conditions,[68] the greater tidal heating experienced by Ganymede,[69] and the more numerous and energetic impacts that would have been suffered by Ganymede during the Late Heavy Bombardment.[70][71][72] The relatively simple geological history of Callisto provides planetary scientists with a reference point for comparison with other more active and complex worlds.[15]

It is speculated that there could be life in Callisto's subsurface ocean. Like Europa and Ganymede, as well as Saturn's moons Enceladus, Dione and Titan and Neptune's moon Triton,[73] a possible subsurface ocean might be composed of salt water.

It is possible that halophiles could thrive in the ocean.[74]As with Europa and Ganymede, the idea has been raised that habitable conditions and even extraterrestrial microbial life may exist in the salty ocean under the Callistoan surface.[23] However, the environmental conditions necessary for life appear to be less favorable on Callisto than on Europa. The principal reasons are the lack of contact with rocky material and the lower heat flux from the interior of Callisto.[23] Scientist Torrence Johnson said the following about comparing the odds of life on Callisto with the odds on other Galilean moons:[74]

The basic ingredients for lifewhat we call 'pre-biotic chemistry'are abundant in many solar system objects, such as comets, asteroids and icy moons. Biologists believe liquid water and energy are then needed to actually support life, so it's exciting to find another place where we might have liquid water. But, energy is another matter, and currently, Callisto's ocean is only being heated by radioactive elements, whereas Europa has tidal energy as well, from its greater proximity to Jupiter.

Based on the considerations mentioned above and on other scientific observations, it is thought that of all of Jupiter's moons, Europa has the greatest chance of supporting microbial life.[23][75]

The Pioneer 10 and Pioneer 11 Jupiter encounters in the early 1970s contributed little new information about Callisto in comparison with what was already known from Earth-based observations.[6] The real breakthrough happened later with the Voyager 1 and Voyager 2 flybys in 1979. They imaged more than half of the Callistoan surface with a resolution of 12km, and precisely measured its temperature, mass and shape.[6] A second round of exploration lasted from 1994 to 2003, when the Galileo spacecraft had eight close encounters with Callisto, the last flyby during the C30 orbit in 2001 came as close as 138km to the surface. The Galileo orbiter completed the global imaging of the surface and delivered a number of pictures with a resolution as high as 15meters of selected areas of Callisto.[18] In 2000, the Cassini spacecraft en route to Saturn acquired high-quality infrared spectra of the Galilean satellites including Callisto.[48] In FebruaryMarch 2007, the New Horizons probe on its way to Pluto obtained new images and spectra of Callisto.[76]

The next planned mission to the Jovian system is the European Space Agency's Jupiter Icy Moon Explorer (JUICE), due to launch in 2023.[77] Several close flybys of Callisto are planned during the mission.[78]

Formerly proposed for a launch in 2020, the Europa Jupiter System Mission (EJSM) was a joint NASA/ESA proposal for exploration of Jupiter's moons. In February 2009 it was announced that ESA/NASA had given this mission priority ahead of the Titan Saturn System Mission.[79] At the time ESA's contribution still faced funding competition from other ESA projects.[80] EJSM consisted of the NASA-led Jupiter Europa Orbiter, the ESA-led Jupiter Ganymede Orbiter, and possibly a JAXA-led Jupiter Magnetospheric Orbiter.

In 2003 NASA conducted a conceptual study called Human Outer Planets Exploration (HOPE) regarding the future human exploration of the outer Solar System. The target chosen to consider in detail was Callisto.[24][82]

The study proposed a possible surface base on Callisto that would produce rocket propellant for further exploration of the Solar System.[81] Advantages of a base on Callisto include low radiation (due to its distance from Jupiter) and geological stability. Such a base could facilitate remote exploration of Europa, or be an ideal location for a Jovian system waystation servicing spacecraft heading farther into the outer Solar System, using a gravity assist from a close flyby of Jupiter after departing Callisto.[24]

In December 2003, NASA reported that a manned mission to Callisto might be possible in the 2040s.[83]

Links to related articles

The rest is here:
Callisto (moon) - Wikipedia

The Moon is Earth's largest natural satellite. We usually see it in the night sky. Some other planets also have moons or natural satellites.

Our moon is about a quarter the size of the Earth. Because it is far away it looks small, about half a degree wide. The gravity on the moon is one-sixth of the Earth's gravity.[8] It means that something will be one-sixth as heavy on the Moon than on Earth. The Moon is a rocky and dusty place. It moves slowly away from the earth at a rate of 3.8 cm per year, due to the effect of tidal dissipation.

Because the moon is round, half of it is lit up by the sun. As it goes around (or orbits) the Earth, sometimes the side that people on Earth can see is all lit brightly. Other times only a small part of the side we see is lit. This is because the Moon does not send out its own light. People only see the parts that are being lit by sunlight. These different stages are called Phases of the Moon.

It takes the Moon about 29.53 days (29 days, 12hours, 44minutes) to complete the cycle, from big and bright to small and dim and back to big and bright. The phase when the Moon passes between the Earth and Sun is called the new moon. The next phase of the moon is called the "waxing crescent", followed by the "first quarter", "waxing gibbous", then to a full moon. A full Moon occurs when the moon and sun are on opposite sides of the Earth. As the Moon continues its orbit it becomes a "waning gibbous", "third quarter", "waning crescent", and finally back to a new moon. People used the moon to measure time. A month is approximately equal in time to a lunar cycle.

The moon always shows the same side to Earth. Astronomers call this phenomenon tidal locking. This means that half of it can never be seen from Earth. The side facing away from Earth is called the far side or dark side of the Moon even though the sun does shine on itwe just never see it lit.

Before people stood on the Moon, the United States and the USSR sent robots to the Moon. These robots would orbit the Moon or land on its surface. The robots were the first man-made objects to touch the Moon.

Humans finally landed on the Moon on July 21, 1969.[9] Astronauts Neil Armstrong and Buzz Aldrin landed their lunar ship (the Eagle) on the surface of the moon. Then, as half the world watched him on television, Armstrong climbed down the ladder of the Eagle and was the first human to touch the Moon as he said, "That's one small step for a man, one giant leap for mankind."

Even though their footprints were left on the moon a long time ago, it is likely that they are still there, as there is no wind or rain, making erosion extremely slow. The footprints do not get filled in or smoothed out.

More people landed on the moon between 1969 and 1972, when the last spaceship, Apollo 17 visited. Eugene Cernan of Apollo 17 was the last person to touch the moon.

Because it is smaller, the Moon has less gravity than Earth (only 1/6 of the amount on Earth). So if a person weighs 120kg on Earth, the person would only weigh 20kg on the moon. But even though the Moon's gravity is weaker than the Earth's gravity, it is still there. If person dropped a ball while standing on the moon, it would still fall down. However, it would fall much more slowly. A person who jumped as high as possible on the moon would jump higher than on Earth, but still fall back to the ground. Because the Moon has no atmosphere, there is no air resistance, so a feather will fall as fast as a hammer.[10]

Without an atmosphere, the environment is not protected from heat or cold. Astronauts wore spacesuits, and carried oxygen to breathe. The suit weighed about as much as the astronaut. The Moon's gravity is weak, so it was not as heavy as on Earth.

In the Earth, the sky is blue because the blue rays of the sun bounce off the gases in the atmosphere, making it look like blue light is coming from the sky. But on the moon, because there is no atmosphere, the sky looks black, even in the daytime. There is no atmosphere to protect the moon from the rocks that fall from outer space, and these meteorites crash right into the moon and make wide, shallow holes called craters. The moon has thousands of them. Newer craters gradually wear away the older ones.

The giant impact hypothesis is that the Moon was created out of the debris from a collision between the young Earth and a Mars-sized protoplanet. This is the favored scientific hypothesis for the formation of the Moon.[11]

In 2009 NASA said that they had found a lot of water on the moon.[12] The water is not liquid but is in the form of hydrates and hydroxides. Liquid water cannot exist on the Moon because photodissociation quickly breaks down the molecules. However, from the data NASA received, liquid surface water may have once existed on the moon.

During the Cold War, the United States Army thought about making a military post on the Moon, able to attack targets on Earth. They also considered conducting a nuclear weapon test on the Moon.[13] The United States Air Force had similar plans.[14][15] However, both plans were brushed-off as NASA moved from a military to a civilian-based agency.

Even though the Soviet Union left remains on the Moon, and the United States left a few flags, no country has control over the Moon.[16] The U.S. and Soviet Union both signed the Outer Space Treaty,[17] which calls the Moon and all of outer space the "province of all mankind". This treaty also banned all use of the military of the Moon, including nuclear weapons tests and military bases.

Media related to Moon at Wikimedia Commons

Read more here:
Moon - Simple English Wikipedia, the free encyclopedia

Lunar phase: completely illuminated disc

The full moon is the lunar phase when the Moon appears fully illuminated from Earth's perspective. This occurs when Earth is located between the Sun and the Moon (more exactly, when the ecliptic longitudes of the Sun and Moon differ by 180).[3] This means that the lunar hemisphere facing Earth the near side is completely sunlit and appears as a circular disk. The full moon occurs roughly once a month.

The time interval between a full moon and the next repetition of the same phase, a synodic month, averages about 29.53 days. Therefore, in those lunar calendars in which each month begins on the day of the new moon, the full moon falls on either the 14th or 15th day of the lunar month. Because a calendar month consists of a whole number of days, a month in a lunar calendar may be either 29 or 30 days long.

A full moon is often thought of as an event of a full night's duration, although its phase seen from Earth continuously waxes or wanes, and is full only at the instant when waxing ends and waning begins. For any given location, about half of these maximum full moons may be visible, while the other half occurs during the day, when the full moon is below the horizon.

Many almanacs list full moons not only by date, but also by their exact time, usually in Coordinated Universal Time (UTC). Typical monthly calendars that include lunar phases may be offset by one day when prepared for a different time zone.

The full moon is generally a suboptimal time for astronomical observation of the Moon because shadows vanish. It is a poor time for other observations because the bright sunlight reflected by the Moon, amplified by the opposition surge, then outshines many stars.

On 12 December 2008, the full moon was closer to the Earth than it had been at any time in the previous 15 years. This was referred to in popular media as a supermoon.[4]

On 19 March 2011, there was another full "supermoon", closer to the Earth than at any time in the previous 18 years.[5]

On 14 November 2016, there was another full "supermoon"; this time it was closer to the Earth than at any time in the previous 68 years.[6]

The date and approximate time of a specific full moon (assuming a circular orbit) can be calculated from the following equation:[7]

where d is the number of days since 1 January 2000 00:00:00 in the Terrestrial Time scale used in astronomical ephemerides; for Universal Time (UT) add the following approximate correction to d:

where N is the number of full moons since the first full moon of 2000. The true time of a full moon may differ from this approximation by up to about 14.5 hours as a result of the non-circularity of the Moon's orbit.[8] See New moon for an explanation of the formula and its parameters.

The age and apparent size of the full moon vary in a cycle of just under 14 synodic months, which has been referred to as a full moon cycle.

When the Moon moves into Earth's shadow, a lunar eclipse occurs, during which all or part of the Moon's face may appear reddish due to the Rayleigh scattering of blue wavelengths and the refraction of sunlight through Earth's atmosphere.[9][10][11] Lunar eclipses happen only during a full moon and around points on its orbit where the satellite may pass through the planet's shadow. A lunar eclipse does not occur every month because the Moon's orbit is inclined 5.14 with respect to the ecliptic plane of Earth; thus, the Moon usually passes north or south of Earth's shadow, which is mostly restricted to this plane of reference. Lunar eclipses happen only when the full moon occurs around either node of its orbit (ascending or descending). Therefore, a lunar eclipse occurs about every six months, and often two weeks before or after a solar eclipse, which occurs during a new moon around the opposite node.

Full moons are traditionally associated with insomnia (inability to sleep), insanity (hence the terms lunacy and lunatic) and various "magical phenomena" such as lycanthropy. Psychologists, however, have found that there is no strong evidence for effects on human behavior around the time of a full moon.[12] They find that studies are generally not consistent, with some showing a positive effect and others showing a negative effect. In one instance, the 23 December 2000 issue of the British Medical Journal published two studies on dog bite admission to hospitals in England and Australia. The study of the Bradford Royal Infirmary found that dog bites were twice as common during a full moon, whereas the study conducted by the public hospitals in Australia found that they were less likely.

Historically, month names are names of moons (lunations, not necessarily full moons) in lunisolar calendars. Since the introduction of the solar Julian calendar in the Roman Empire, and later the Gregorian calendar worldwide, people no longer perceive month names as "moon" names. The traditional Old English month names were equated with the names of the Julian calendar from an early time (soon after Christianization, according to the testimony of Bede around AD 700).

Some full moons have developed new names in modern times, such as "blue moon", as well as "harvest moon" and "hunter's moon" for the full moons of autumn.

Lunar eclipses occur only at a full moon and often cause a reddish hue on the near side of the Moon. This full moon has been called a blood moon in popular culture.[13]

The "harvest moon" and the "hunter's moon" are traditional names for the full moons in late summer and in the autumn in the Northern Hemisphere, usually in September and October, respectively. It is celebrated by festivities such as the Chinese Mid-Autumn Festival, which is on par the Chinese New Year in importance.

The "harvest moon" (also known as the "barley moon" or "full corn moon") is the full moon nearest to the autumnal equinox (22 or 23 September), occurring anytime within two weeks before or after that date.[15] The "hunter's moon" is the full moon following it. The names are recorded from the early 18th century.[16] The Oxford English Dictionary entry for "harvest moon" cites a 1706 reference, and for "hunter's moon" a 1710 edition of The British Apollo, where the term is attributed to "the country people" ("The Country People call this the Hunters-Moon.") The names became traditional in American folklore, where they are now often popularly attributed to Native Americans.[17] The Feast of the Hunters' Moon is a yearly festival in West Lafayette, Indiana, held in late September or early October each year since 1968.[18] In 2010, the harvest moon occurred on the night of the equinox itself (some 512 hours after the moment of equinox) for the first time since 1991.[19][20]

All full moons rise around the time of sunset. Since the moon moves eastward among the stars faster than the sun, lunar culmination is delayed by about 50.47 minutes[21] (on average) each day, thus causing moonrise to occur later each day.

Due to the high lunar standstill, the harvest and hunter's moons of 2007 were special because the time difference between moonrises on successive evenings was much shorter than average. The moon rose about 30 minutes later from one night to the next, as seen from about 40 N or S latitude (because the full moon of September 2007 rose in the northeast rather than in the east). Hence, no long period of darkness occurred between sunset and moonrise for several days after the full moon,[22] thus lengthening the time in the evening when there is enough twilight and moonlight to work to get the harvest in.

The Maine Farmers' Almanac from around the 1930s began to publish Native American "Indian" full moon names, some of which had been adopted by colonial Americans.[23] The Farmers' Almanac (since 1955 published in Maine, but not the same publication as the Maine Farmers' Almanac) continues to do so.[24]

An early list of "Indian month names" was published in 1918 by Daniel Carter Beard in his The American Boy's Book of Signs, Signals and Symbols for use by the boy scouts. Beard's "Indian" month names were:[25]

Such names have gained currency in American folklore. They appear in print more widely outside of the almanac tradition from the 1990s in popular publications about the Moon.Mysteries of the Moon by Patricia Haddock ("Great Mysteries Series", Greenhaven Press, 1992) gave an extensive list of such names along with the individual tribal groups they were supposedly associated with.[26] Haddock supposes that certain "Colonial American" moon names were adopted from Algonquian languages (which were formerly spoken in the territory of New England), while others are based in European tradition (e.g. the Colonial American names for the May moon, "Milk Moon", "Mother's Moon", "Hare Moon" have no parallels in the supposed native names, while the name of November, "Beaver Moon" is supposedly based in an Algonquian language).

The individual names (some inconsistent) given in Farmers' Almanac, which is not authoritative, include the following:[clarification needed]

The Long Night's Moon is the last full moon of the year and the one nearest the winter solstice.[28]

"Ice Moon" is also used to refer to the first full moon of January or February.[29]

In Hinduism, most festivals are celebrated on auspicious days. Many of the Hindu festivals are celebrated on days with a full moon at night.Different parts of India celebrate the same day with different names, as listed below:

Most pre-modern calendars the world over were lunisolar, combining the solar year with the lunation by means of intercalary months.[35][36]The Julian calendar abandoned this method in favour of a purely solar reckoning while conversely the 7th-century Islamic calendar opted for a purely lunar one.

A continuing lunisolar calendar is the Hebrew calendar. Evidence of this is noted in the dates of Passover and Easter in Judaism and Christianity, respectively. Passover falls on the full moon on 15 Nisan of the Hebrew calendar. The date of the Jewish Rosh Hashana and Sukkot festivals along with all other Jewish holidays are dependent on the dates of the new moons.[37]

In lunisolar calendars, an intercalary month occurs seven times in the 19 years of the Metonic cycle, or on average every 2.7 years (19/7). In the Hebrew calendar this is noted with a periodic extra month of Adar in the early spring.

In the modern system of "traditional" American full moon names tied to the solstice and equinox points, a supernumerary full moon in such a period is called a blue moon. The term "blue moon" used in this sense may date to as early as the 16th century, but it became well known in the United States due to the Farmers' Almanac (published since 1818).[a]

According to the pattern of use in the Farmers' Almanac, a "blue moon" is the third full moon in any period between either a solstice and an equinox, or between an equinox and a solstice, (calculated using the mean tropical year), which contains four full moons.[39] These seasons are equal in length, unlike the astronomical ones, which vary in length depending on the Earth's speed in its elliptical orbit round the Sun. To compare, in 1983 the equal-length mean-solar solar points and the actual astronomical (observed) dates are shown in the table below (all dates & times in GMT):

As a consequence of checking an inadequate number of old issues of the Farmers' Almanac, the author of an article in the March1946 issue of Sky & Telescope magazine wrongly concluded that the Farmers' Almanac had used "blue moon" to denote "the second full moon in any month which contains two full moons".

The mistaken rule was retracted and declared "erroneous" in a 1999 Sky & Telescope article, which gave the corrected rule, based on order in seasons.[40]

Using either meaning, "blue moons" occur with the same average frequency of intercalary months, 7times in 19years; the Farmers' Almanac system of full moon names effectively defines a functioning luni-solar calendar.

View original post here:
Full moon - Wikipedia

Frozen carbon dioxide on the moon may be essential to colonization, scientists say, after the existence of carbon dioxide cold traps on the lunar surface were confirmed.

At the moons poles, permanently shadowed regions can get colder than the coldest areas of Pluto, and it has long been theorized that carbon dioxide cold traps could exist there. Frozen carbon dioxide would have numerous beneficial applications in establishing a sustained presence on the moon.

I think when I started this, the question was, Can we confidently say there are carbon dioxide cold traps on the moon or not? said lead author Norbert Schrghofer of the Planetary Sciences Institute. He admitted his surprise that there are indeed contiguous regions which are cold enough, beyond doubt.

Though the cold traps have finally been confirmed and mapped, in a study published in Geophysical Research Letters, the authors caution that still doesnt guarantee the presence of frozen CO2.

If solid carbon dioxide is found on the moon, future missions could possibly tap it to produce rocket fuel, biomaterials and even steel, the researchers say. In 2020, molecular water was found on the lunar surface, also bolstering confidence in the sustainability of robotic and human exploration and colonization.

Scientists analyzed more than a decade of temperature data from the Diviner Lunar Radiometer Experiment, which is aboard NASAs Lunar Reconnaissance Orbiter. The cold traps researchers identified included several pockets at the moons southern pole covering an area of about 79 square miles. The largest expanse at 32 square miles was found in the Amundsen Crater. The temperature there is about minus 352 degrees Fahrenheit.

The cold traps can keep carbon dioxide in a solid state even during the rising temperatures of the lunar summer. The study of lunar carbon dioxide and other potential volatile organics, chemical elements and compounds that can be readily vaporized, may help researchers to probe the origin of water and other elements on the moon.

Now that the traps have been confirmed, international policy decisions will have to be made regarding lunar resource extraction, and continued study. Because of the potential uses, the presence of carbon dioxide cold traps has attracted both private companies and governments, researchers say.

These should be high-priority sites to target for future landed missions, said Paul Hayne of the University of Colorado, who was not involved in the study. This sort of pinpoints where you might go on the lunar surface to answer some of these big questions about volatiles on the moon and their delivery from elsewhere in the solar system.

Edited by Richard Pretorius and Kristen Butler

See the original post:
N-Ice-A We Have A Breakthrough: How Frozen CO2 Could Help Create Moon Colonies - Birmingham Times

The term Brujeria has been used in many ways and depicted in different cultures over the years.

A Spanish term, Brujeria formally means witchcraft and is used to "describe or disparage occult religious practices in some Latin American and Afro-Caribbean cultures with indigenous roots."

The more colloquial and modern Brujeria meaning, according to Urban Dictionary, is witchcraft that causes a person to experience a string of bad luck.

RELATED:Did TikTok Witches Hex The Moon? The Truth Behind This WitchTok Rumor

Prior to being colonized, women were the predominant practitioners of Brujeria and were typically regarded as healers and midwives.

In the 16th century, women of all social levels lost most of their legal autonomy after marriage while their husbands retained the right to beat their wives or have illicit affairs.

So, rather than counting on a judiciary and religious system that would only let them down, women turned to sexual magic and witchcraft to combat omnipresent patriarchal domination.

Since Latin America was colonized by Europeans in the 15th century, some native healing medicine and magical traditions combined with the Roman Catholic Church led to hybridity in contemporary spirituality.

Because Brujeria was not based upon Christian ideologies as it didnt worship a Christian God or comply with the Catholic Churchs religious roles and functions, the practice immediately created a clash between Old World and New World beliefs.

Spaniards didnt understand the Brujeria practice and the cultural influence, especially when it came to the women who undertook leadership roles within the Afro and Indigenous cultures.

They saw Brujeria as superstitious and primitive.

Brujera became a taboo practice that warranted prosecution and, for those considered full-blown witches, execution.

As a result of colonization, Indigenous communities were forced to convert to Catholicism, meaning their own religion of Brujeria was invalidated.In the 15th and 16th centuries, the Catholic Churchidentified brujas/brujos as witches.

So Paulo-based Wiccan Priestess Marlia de Abreu details how witchcraft came to So Paulo by way of its Indigenous peoples, European immigrants, enslaved Africans, as well as through Cuban Santera, among other traditions, as a form of resistance and self-identity.

The colonizers found Indigenous magic here and later with slavery, African magic,"Abreu saysin an interview with Teen Vogue."The natives were aware of native medicinal herbs for diseases that the colonizer had no medicine for. For the black people who came as slaves, their magic was also a form of resistance and a way of maintaining their ancestral cultural roots, Abreu says in an interview with Teen Vogue.

Many of the rituals in Brujeria are based on the procedures, practices, and attitudes passed down by its participants and heavily depend on forces of nature and the spontaneity of the spirits.

The practice of Brujeria has been passed down from generation to generation despite the racism, oppression, and isolation of the spiritual practices.

It involvescharms, divination,love spells, and hexescast bybrujas (female), brujos (male), or brujix (genderqueer).

Today, many Latinx people are embracing their Brujeria identity, wanting to spread the love of their culture and history.

The modern Brujeria movement involves practiceslikecleansing, ancestor worship, lighting candles, and honoring the earth. And in some cases,ceremonies entail wearing all-white, singing, and preparing sacred offerings.

Many Brujas have taken to social media to reclaim their power.

Were reclaiming our power, for far too long have we practiced in secrecy due to fear/society, says Emilia Ortiz, a well-known practitioner of the craft through her Instagram account. Now though? Its our time. The same way other women/femmes are reclaiming their power in other areas this is no different.

Hey You! Want more of YourTango's best articles, seriously addictive horoscopes and top expert advice? Sign up to get our free daily newsletter!

In 2016, Afro-Puerto Rican rapper Princess Nokia released a song called Brujas acknowledging her connection to her ancestors and the spiritual practice.

Mexican-born playwright and television writer Tanya Saracho announced in January2018 that shes developing a television show named "Brujas" that is centered around the Bruja movement in Chicago and follows four Afro-Latinas, though in 2020 Saracho noted that development is currently paused.

Today, much of what was once misunderstood about Brujeria is being corrected by people of color who are allowing people to relearn the cultural importance of the practice.

Its about reclaiming their power and freedom, changing the dialogue, and creating more spaces for Latinx people to celebrate their symbols of power.

There are is always a wayto protect yourself from Brujeria with a method called shielding, which isall about creating a barrier to protect yourself from negative energy.

An energy barrier is like a second skin, and it can keepyou safe from any magicalinfluences or threats that you might encounter in your life.

To begin shielding,you must spend time sensing your own energyand moving it in one direction then another, focusing on what it feels like as well as what you are seeing.

Once you have become acquainted with your energy, begin pushing it to expand around your body. This is the part where you visualize it as a second skin.

Maintain this solid energy skin and push against outside forces whenever you feel the need. It takes time and practice to perfect the act of shielding but offers a high reward in the end.

Nia Tipton is a writer living in Brooklyn. She covers pop culture, social justice issues, and trending topics.Follow her on Instagram.

See the article here:
What Is A Bruja Or Brujo in Witchcraft? Brujeria Meaning Explained - YourTango