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67-525: The interplanetary medium includes interplanetary dust , cosmic rays , and hot plasma from the solar wind . The density of the interplanetary medium is very low, decreasing in inverse proportion to the square of the distance from the Sun. It is variable, and may be affected by magnetic fields and events such as coronal mass ejections . Typical particle densities in the interplanetary medium are about 5-40 particles/cm, but exhibit substantial variation. In

134-445: A vacuum filled with an " aether ", or just a cold, dark vacuum continued up until the 1950s. Tufts University Professor of astronomy, Kenneth R. Lang, writing in 2000 noted, "Half a century ago, most people visualized our planet as a solitary sphere traveling in a cold, dark vacuum of space around the Sun". In 2002, Akasofu stated "The view that interplanetary space is a vacuum into which the Sun intermittently emitted corpuscular streams

201-534: A definite determination of the source of the problem, as LEAM operated only briefly before the Apollo program ended. It is possible that these storms have been spotted from Earth: For centuries, there have been reports of strange glowing lights on the Moon, known as " transient lunar phenomena " or TLPs. Some TLPs have been observed as momentary flashes, now generally accepted to be visible evidence of meteoroids impacting

268-477: A difference of ratio of mineral phases. The primary minerals identified in Lunar regolith are plagioclase , olivine , augite , orthopyroxene , pigeonite , ilmenite , chromite , quartz , cristobalite , and whitlockite . Glass is abundant in the Lunar regolith and forms as a result of impact melting. Ice is an important mineral in permanently shaded craters. Lunar regolith is divided into highland and mare on

335-401: A human Mars expedition, and ranked "dust" as the number one challenge. The report urged study of its mechanical properties, corrosiveness, grittiness, and effect on electrical systems. Most scientists think the only way to answer the questions definitively is by returning samples of Martian dirt and rock to Earth well before launching any astronauts. Although that report addressed Martian dust,

402-562: A program for atmospheric collection and curation of these particles was developed at Johnson Space Center in Texas. This stratospheric micrometeorite collection, along with presolar grains from meteorites, are unique sources of extraterrestrial material (not to mention being small astronomical objects in their own right) available for study in laboratories today. Spacecraft that have carried dust detectors include Helios , Pioneer 10 , Pioneer 11 , Ulysses (heliocentric orbit out to

469-594: A result long-term space missions could require complicated and expensive efforts to provide food, such as importing Earth soil , chemically treating lunar regolith to remove heavy metals and oxidize iron atoms, and selectively breeding strains of plants that are adapted to the inhospitable lunar regolith. Therefore lunar regolith has been tested, successfully growing plants from it in a laboratory on Earth. The Apollo astronauts brought back some 360 kilograms (790 lb) of lunar rocks from six landing sites. Although this material has been isolated in vacuum-packed bottles, it

536-403: A tenuous layer of moving dust particles constantly leaping up from and falling back to the Moon's surface, giving rise to a "dust atmosphere" that looks static but is composed of dust particles in constant motion. The term "Moon fountain" has been used to describe this effect by analogy with the stream of molecules of water in a fountain following a ballistic trajectory while appearing static due to

603-468: Is also responsible for the strength of the Sun's magnetic field at the orbit of the Earth being over 100 times greater than originally anticipated. If space were a vacuum, then the Sun's 10 tesla magnetic dipole field would reduce with the cube of the distance to about 10 tesla. But satellite observations show that it is about 100 times greater at around 10 tesla. Magnetohydrodynamic (MHD) theory predicts that

670-455: Is because lunar dust is more chemically reactive and has larger surface areas composed of sharper jagged edges than Earth dust. If the chemically reactive particles are deposited in the lungs, they may cause respiratory disease. Long-term exposure to the dust may cause a more serious respiratory disease similar to silicosis . During lunar exploration the astronauts' spacesuits will become contaminated with lunar dust. The dust will be released into

737-449: Is composed of various types of particles including rock fragments, mono-mineralic fragments, and various kinds of glasses including agglutinate particles, volcanic and impact spherules. The agglutinates form at the lunar surface by micrometeorite impacts that cause small-scale melting which fuses adjacent materials together with tiny specks of elemental iron embedded in each dust particle's glassy shell. There are two primary differences in

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804-583: Is dominant over the Sun 's. This disrupts the flow of the solar wind, which is channelled around the magnetosphere. Material from the solar wind can "leak" into the magnetosphere, causing aurorae and also populating the Van Allen radiation belts with ionised material. The interplanetary medium is responsible for several optical phenomena visible from Earth. Zodiacal light is a broad band of faint light sometimes seen after sunset and before sunrise, stretched along

871-447: Is gone. The chemical and electrostatic properties of the dirt no longer match what future astronauts will encounter on the Moon. Moon dust-contaminated items finally became available to the public in 2014, when the US government approved the sale of private material owned, and collected, by astronauts. Since then only one item has been produced for sale with genuine Moon dust collected after

938-401: Is now unusable for detailed chemical or mechanical analysis—the gritty particles deteriorated the knife-edge indium seals of the vacuum bottles; air has slowly leaked in. Every sample brought back from the Moon has been contaminated by Earth's air and humidity. The dust has acquired a patina of rust, and, as a result of bonding with terrestrial water and oxygen molecules, its chemical reactivity

1005-418: Is so rarefied , it does not exhibit thermodynamic equilibrium . Instead, different components have different temperatures. The solar wind exhibits temperatures consistent with Chapman's estimate in cislunar space , and dust particles near Earth's orbit exhibit temperatures 257–298 K (3–77 °F), averaging about 283 K (50 °F). In general, the solar wind temperature decreases proportional to

1072-515: Is the most prominent feature of the night sky 's radiation, with wavelengths ranging 5–50 μm . The particle sizes of grains characterizing the infrared emission near Earth's orbit typically range 10–100 μm. Microscopic impact craters on lunar rocks returned by the Apollo Program revealed the size distribution of cosmic dust particles bombarding the lunar surface. The ’’Grün’’ distribution of interplanetary dust at 1 AU, describes

1139-488: Is the unconsolidated material found on the surface of the Moon and in the Moon's tenuous atmosphere . Sometimes referred to as Lunar soil, Lunar soil specifically refers to the component of regolith smaller than 1 cm. It differs substantially in properties from terrestrial soil . As the Moon's fine surface layer, lunar regolith is picked up by even weak natural phenomena active at the Moon's surface, allowing it to be part of

1206-508: The ecliptic and appearing brightest near the horizon. This glow is caused by sunlight scattered by dust particles in the interplanetary medium between Earth and the Sun. A similar phenomenon centered at the antisolar point , gegenschein is visible in a naturally dark, moonless night sky . Much fainter than zodiacal light, this effect is caused by sunlight backscattered by dust particles beyond Earth's orbit. The term "interplanetary" appears to have been first used in print in 1691 by

1273-439: The lunar regolith has acted as a collector for solar wind particles, and so studies of rocks from the lunar surface can be valuable in studies of the solar wind. High-energy particles from the solar wind impacting on the lunar surface also cause it to emit faintly at X-ray wavelengths. Planets with their own magnetic field, such as the Earth and Jupiter , are surrounded by a magnetosphere within which their magnetic field

1340-663: The 1970s linked the zodiacal light with the interplanetary dust cloud in the Solar System. Also, the VBSDC instrument on the New Horizons probe was designed to detect impacts of the dust from the zodiacal cloud in the Solar System. The sources of interplanetary dust particles (IDPs) include at least: asteroid collisions, cometary activity and collisions in the inner Solar System, Kuiper belt collisions, and interstellar medium grains (Backman, D., 1997). The origins of

1407-486: The 1970s using balloons and then U-2 aircraft. Although some of the particles found were similar to the material in present-day meteorite collections, the nanoporous nature and unequilibrated cosmic-average composition of other particles suggested that they began as fine-grained aggregates of nonvolatile building blocks and cometary ice. The interplanetary nature of these particles was later verified by noble gas and solar flare track observations. In that context

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1474-433: The Earth's crust. In the case of the regolith, this is due in part to the constant bombardment of the lunar surface with protons from the solar wind. One consequence is that iron on the Moon is found in the elemental (0) and cationic (+2) oxidation states, whereas on Earth iron is found primarily in the +2 and +3 oxidation states. A 2005 NASA study listed 20 risks that required further study before humans should commit to

1541-410: The Moon . Lunar regolith is primarily the result of mechanical weathering . Continual meteoric impacts and bombardment by solar and interstellar charged atomic particles of the lunar surface over billions of years ground the basaltic and anorthositic rock, the regolith of the Moon, into progressively finer material. This situation contrasts fundamentally to terrestrial soil formation, mediated by

1608-404: The Moon's scant atmosphere. It is easily disturbed and poses a significant hazard to exposed equipment and human health. The fine lunar regolith is made of sharp and very adhesive particles, with a distinct gunpowder taste and smell. Lunar regolith is prospected as a lunar resource , particularly for lunar in situ utilization , such as a lunar building material and regolith for growing plants on

1675-477: The Moon's surface called LEAM , short for Lunar Ejecta and Meteorites. It was designed to look for dust kicked up by small meteoroids hitting the Moon's surface. It had three sensors that could record the speed, energy, and direction of tiny particles: one each pointing up, east, and west. LEAM saw a large number of particles every morning, mostly coming from the east or west—rather than above or below—and mostly slower than speeds expected for lunar ejecta. In addition,

1742-555: The Moon. It is the first lunar regolith sample to return to Earth since 1976. China is the third country in the world to have brought such material back to Earth. Chang'e-5 is part of the first phase of the Chinese Lunar Exploration Program . Chang'e 6 collected and returned samples from the far side of the Moon in 2024. There are still two projects left in this phase of the program (Chang'e-7 in 2024 and Chang'e-8 in 2027). The program's second phase

1809-449: The Sun into interstellar space. The interplanetary dust cloud has a complex structure (Reach, W., 1997). Apart from a background density, this includes: Interplanetary dust has been found to form rings of dust in the orbital space of Mercury and Venus. Venus's orbital dust ring is suspected to originate either from yet undetected Venus trailing asteroids, interplanetary dust migrating in waves from orbital space to orbital space, or from

1876-532: The Zodiacal Cloud structure; synthesis of observations; instrumentation; physical processes; optical properties of interplanetary dust; orbital evolution of interplanetary dust; circumplanetary dust, observations and simple physics; interstellar dust and circumstellar dust disks. 2019 Rafael Rodrigo, Jürgen Blum, Hsiang-Wen Hsu, Detlef V. Koschny, Anny-Chantal Levasseur-Regourd , Jesús Martín-Pintado, Veerle J. Sterken, and Andrew Westphal collected reviews in

1943-458: The atmosphere when the suits are removed. The methods used to mitigate exposure will include providing high air recirculation rates in the airlock, the use of a "Double Shell Spacesuit", the use of dust shields, the use of high–grade magnetic separation, and the use of solar flux to sinter and melt the regolith. Anecdotal reports of human exposures to lunar dust during the Apollo program suggest that lunar dust has toxic properties. After each EVA,

2010-416: The basis of their composition, and further divided into high-, low-, and very low-titanium on the basis of their ilmenite content. The contribution of material from external sources is relatively minor (outside of ray systems ), such that the dirt composition at any given location largely reflects the local bedrock composition. Lunar regolith reportedly taste and smell of spent gunpowder . Lunar regolith

2077-624: The book Cosmic Dust from the Laboratory to the Stars . Included are discussions of dust in various environments: from planetary atmospheres and airless bodies over interplanetary dust, meteoroids, comet dust and emissions from active moons to interstellar dust and protoplanetary disks. Diverse research techniques and results, including in-situ measurement, remote observation, laboratory experiments and modelling, and analysis of returned samples are discussed. Lunar regolith Lunar regolith

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2144-404: The characteristics of a plasma, rather than a simple gas. For example, it carries the Sun's magnetic field with it, is highly electrically conductive (resulting in the heliospheric current sheet ), forms plasma double layers where it comes into contact with a planetary magnetosphere or at the heliopause , and exhibits filamentation (such as in aurorae ). The plasma in the interplanetary medium

2211-404: The chemistry of lunar regolith and dirt from terrestrial materials. The first is that the Moon is very dry. As a result, those minerals with water as part of their structure ( mineral hydration ) such as clay , mica , and amphiboles are absent from the Moon's surface. The second difference is that lunar regolith and crust are chemically reduced , rather than being significantly oxidized like

2278-414: The concerns are equally valid concerning lunar dust. The dust found on the lunar surface could cause harmful effects on any human outpost technology and crew members: The principles of astronautical hygiene should be used to assess the risks of exposure to lunar dust during exploration on the Moon's surface and thereby determine the most appropriate measures to control exposure. These may include removing

2345-405: The constancy of the stream. According to a model proposed in 2005 by the Laboratory for Extraterrestrial Physics at NASA 's Goddard Space Flight Center , this is caused by electrostatic levitation . On the daylit side of the Moon, solar hard ultraviolet and X-ray radiation is energetic enough to knock electrons out of atoms and molecules in the lunar regolith. Positive charges build up until

2412-421: The crew modules were heavily contaminated with dust; many astronauts reported coughs, throat irritation, watery eyes, and blurred vision that likely reduced their performance. A flight surgeon exposed to the capsule interiors after recovery developed what appeared to be allergic reactions to lunar dust that worsened after each exposure. The apparent toxic effects of lunar dust were never comprehensively studied after

2479-423: The cutoff at less than 50  μm in diameter, while others put it at less than 10 μm. The major processes involved in the formation of lunar regolith are: These processes continue to change the physical and optical properties of the dirt over time, and it is known as space weathering . In addition, fire fountaining, whereby volcanic lava is lofted and cools into small glass beads before falling back to

2546-535: The day and night areas, resulting in horizontal dust transport—a form of "Moon storm". This effect was anticipated in 1956 by science fiction author Hal Clement in his short story "Dust Rag", published in Astounding Science Fiction . There is some evidence for this effect. In the early 1960s, Surveyor 7 and several prior Surveyor spacecraft that soft-landed on the Moon returned photographs showing an unmistakable twilight glow low over

2613-482: The distance of Jupiter), Galileo (Jupiter Orbiter), Cassini (Saturn orbiter), and New Horizons (see Venetia Burney Student Dust Counter ). The Solar interplanetary dust cloud obscures the extragalactic background light , making observations of it from the Inner Solar System very limited. Collections of review articles on various aspects of interplanetary dust and related fields appeared in

2680-427: The dynamical effects of planets (Backman, D., 1997). The lifetimes of these dust particles are very short compared to the lifetime of the Solar System. If one finds grains around a star that is older than about 10,000,000 years, then the grains must have been from recently released fragments of larger objects, i.e. they cannot be leftover grains from the protoplanetary disk (Backman, private communication). Therefore,

2747-410: The experiment's temperature increased to near 100 degrees Celsius a few hours after each lunar sunrise, so the unit had to be turned off temporarily because it was overheating. It is speculated that this could have been a result of electrically charged moondust sticking to LEAM, darkening its surface so the experiment package absorbed rather than reflected sunlight. However, scientists were unable to make

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2814-462: The flux of cosmic dust from nm to mm sizes at 1 AU. The total mass of the interplanetary dust cloud is approximately 3.5 × 10  kg , or the mass of an asteroid of radius 15 km (with density of about 2.5 g/cm ). Straddling the zodiac along the ecliptic , this dust cloud is visible as the zodiacal light in a moonless and naturally dark sky and is best seen sunward during astronomical twilight . The Pioneer spacecraft observations in

2881-472: The following books: In 1978 Tony McDonnell edited the book Cosmic Dust which contained chapters on comets along with zodiacal light as indicator of interplanetary dust, meteors, interstellar dust, microparticle studies by sampling techniques, and microparticle studies by space instrumentation. Attention is also given to lunar and planetary impact erosion, aspects of particle dynamics, and acceleration techniques and high-velocity impact processes employed for

2948-408: The grains would be "later-generation" dust. The zodiacal dust in the Solar System is 99.9% later-generation dust and 0.1% intruding interstellar medium dust. All primordial grains from the Solar System's formation were removed long ago. Particles which are affected primarily by radiation pressure are known as "beta meteoroids". They are generally less than 1.4 × 10  g and are pushed outward from

3015-410: The inverse-square of the distance to the Sun; the temperature of the dust decreases proportional to the inverse cube root of the distance. For dust particles within the asteroid belt , typical temperatures range from 200 K (−100 °F) at 2.2 AU down to 165 K (−163 °F) at 3.2 AU. Since the interplanetary medium is a plasma , or gas of ions , the interplanetary medium has

3082-403: The item spent over 32 hours on the Moon. A luggage strap, exposed to the elements of the Moon for 32 hours, a piece of Charles "Pete" Conrad's spacesuit on the Apollo 12 mission, was sold by his estate to a private purchaser at auction. In 2017 lunar regolith collected by Neil Armstrong in 1969 was put up for auction. While many jewelry- and watch-makers claim their product contains "Moon dust",

3149-416: The laboratory simulation of effects produced by micrometeoroids. 2001 Eberhard Grün , Bo Gustafson, Stan Dermott, and Hugo Fechtig published the book Interplanetary Dust . Topics covered are: historical perspectives; cometary dust; near-Earth environment; meteoroids and meteors; properties of interplanetary dust, information from collected samples; in situ measurements of cosmic dust; numerical modeling of

3216-582: The lunar horizon persisting after the Sun had set. Moreover, contrary to the expectation of airless conditions with no atmospheric haze, the distant horizon between land and sky did not look razor-sharp. Apollo 17 astronauts orbiting the Moon in 1972 repeatedly saw and sketched what they variously called "bands," "streamers" or "twilight rays" for about 10 seconds before lunar sunrise or lunar sunset. Such rays were also reported by astronauts aboard Apollo 8, 10, and 15. These might have been similar to crepuscular rays on Earth. Apollo 17 also placed an experiment on

3283-431: The lunar surface. But others have appeared as amorphous reddish or whitish glows or even as dusky hazy regions that change shape or disappear over seconds or minutes. These may have been a result of sunlight reflecting from suspended lunar dust. While the Moon has a faint atmosphere, traffic and impacts of human activity on the Moon could cause clouds of lunar regolith to spread far across the Moon, and possibly contaminate

3350-419: The motion of a conducting fluid (e.g., the interplanetary medium) in a magnetic field induces electric currents which in turn generate magnetic fields, and in this respect it behaves like an MHD dynamo . The outer edge of the heliosphere is the boundary between the flow of the solar wind and the interstellar medium . This boundary is known as the heliopause and is believed to be a fairly sharp transition of

3417-404: The night side would achieve greater electrical tension differences than the day side, possibly launching dust particles to even higher altitudes. This effect could be further enhanced during the portion of the Moon's orbit where it passes through Earth's magnetotail , part of the magnetic field of the Moon . On the terminator there could be significant horizontal electric fields forming between

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3484-399: The order of 110 to 160 astronomical units from the Sun. The interplanetary medium thus fills the roughly spherical volume contained within the heliopause. How the interplanetary medium interacts with planets depends on whether they have magnetic fields or not. Bodies such as the Moon have no magnetic field and the solar wind can impact directly on their surface. Over billions of years,

3551-413: The original state of the Moon and its special scientific content. Due to a myriad of meteorite impacts (with speeds in the range of 20 km/s), the lunar surface is covered with a thin layer of dust. The dust is electrically charged and sticks to any surface with which it comes in contact. The density of lunar regolith is about 1.5 g/cm and increases with depth. Other factors which may affect

3618-466: The presence of molecular oxygen (O 2 ), humidity, atmospheric wind , and a robust array of contributing biological processes. Lunar soil typically refers to only the finer fraction of lunar regolith , which is composed of grains 1 cm in diameter or less, but is often used interchangeably. Lunar dust generally connotes even finer materials than lunar soil . There is no official definition as to what size fraction constitutes "dust"; some place

3685-603: The products only contain pieces of, or dust from, meteorites believed to have originated from the Moon. On 11 September 2020, NASA announced that it is willing to create a market for lunar regolith by calling for proposals to purchase it from commercial suppliers. In May 2022, scientists successfully grew plants using lunar regolith. Thale cress ( Arabidopsis thaliana ) was the first plant to have sprouted and grown on Earth in regolith from another celestial body. On 16 December 2020, China's Chang'e 5 mission returned to Earth with about 2 kilograms of rock and dirt it picked up from

3752-471: The program, and the concentrations of dust that contaminated the spacecraft are not known. In each case, symptoms resolved within 24 hours, and post-flight pulmonary testing found no permanent impacts in the astronauts. The potential of lunar soil for construction of structures has been proposed at least since the proposal of lunarcrete and increasingly tested. The differences between Earth's soil and lunar soil mean that plants struggle to grow in it. As

3819-595: The properties of lunar regolith include large temperature differentials , the presence of a hard vacuum , and the absence of a significant lunar magnetic field , thereby allowing charged solar wind particles to continuously hit the surface of the Moon. The composition of Lunar regolith reflects the composition of the parent rocks it overlies. Over time, material is mixed both vertically and horizontally (a process known as " gardening ") by impact processes. While mare and highland regolith have distinct compositions, their mineral inventories are very similar, rather expressing

3886-456: The relative consistency of Earth's climate . A very hot interplanetary medium remained a minor position among geophysicists as late as 1959, when Chapman proposed a temperature on the order of 10000 K, but observation in Low Earth orbit of the exosphere soon contradicted his position. In fact, both Fourier and Chapman's final predictions were correct: because the interplanetary medium

3953-531: The remains of the Solar System's circumstellar disc , out of which its proto-planetary disc and then itself, the Solar planetary system , formed. In 1951, Fred Whipple predicted that micrometeorites smaller than 100 micrometers in diameter might be decelerated on impact with the Earth's upper atmosphere without melting. The modern era of laboratory study of these particles began with the stratospheric collection flights of Donald E. Brownlee and collaborators in

4020-402: The scientist Robert Boyle : "The air is different from the æther (or vacuum) in the... interplanetary spaces" Boyle Hist. Air . In 1898, American astronomer Charles Augustus Young wrote: "Inter-planetary space is a vacuum, far more perfect than anything we can produce by artificial means..." ( The Elements of Astronomy , Charles Augustus Young, 1898). The notion that space is considered to be

4087-476: The space between planets within planetary systems , such as the Solar System . This system of particles has been studied for many years in order to understand its nature, origin, and relationship to larger bodies. There are several methods to obtain space dust measurement . In the Solar System, interplanetary dust particles have a role in scattering sunlight and in emitting thermal radiation , which

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4154-444: The spacesuit in a three-stage airlock, "vacuuming" the suit with a magnet before removal, and using local exhaust ventilation with a high-efficiency particulate filter to remove dust from the spacecraft's atmosphere. The harmful properties of lunar dust are not well known. Based on studies of dust found on Earth, it is expected that exposure to lunar dust will result in greater risks to health both from acute and chronic exposure. This

4221-465: The surface, can create small but important deposits in some locations, such as the orange dirt found at Shorty Crater in the Taurus-Littrow valley by Apollo 17 , and the green glass found at Hadley–Apennine by Apollo 15 . Deposits of volcanic beads are also thought to be the origin of Dark Mantle Deposits (DMD) in other locations around the Moon. There is some evidence that the Moon has

4288-417: The tiniest particles of lunar dust (measuring 1 micrometre and smaller) are repelled from the surface and lofted anywhere from metres to kilometres high, with the smallest particles reaching the highest altitudes. Eventually they fall back toward the surface where the process is repeated. On the night side, the dust is negatively charged by electrons from the solar wind . Indeed, the fountain model suggests that

4355-505: The vicinity of the Earth , it contains about 5 particles/cm, but values as high as 100 particles/cm have been observed. The temperature of the interplanetary medium varies through the solar system. Joseph Fourier estimated that interplanetary medium must have temperatures comparable to those observed at Earth's poles , but on faulty grounds : lacking modern estimates of atmospheric heat transport , he saw no other means to explain

4422-671: The zodiacal cloud have long been subject to one of the most heated controversies in the field of astronomy. It was believed that IDPs had originated from comets or asteroids whose particles had dispersed throughout the extent of the cloud. However, further observations have suggested that Mars dust storms may be responsible for the zodiacal cloud's formation. The main physical processes "affecting" (destruction or expulsion mechanisms) interplanetary dust particles are: expulsion by radiation pressure , inward Poynting-Robertson (PR) radiation drag , solar wind pressure (with significant electromagnetic effects), sublimation , mutual collisions, and

4489-583: Was changed radically by Ludwig Biermann (1951, 1953) who proposed on the basis of comet tails, that the Sun continuously blows its atmosphere out in all directions at supersonic speed" ( Syun-Ichi Akasofu , Exploring the Secrets of the Aurora , 2002) Interplanetary dust cloud The interplanetary dust cloud , or zodiacal cloud (as the source of the zodiacal light ), consists of cosmic dust (small particles floating in outer space ) that pervades

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