Interplanetary dust cloud
Encyclopedia
The interplanetary dust cloud is cosmic dust
(small particles floating in space) which pervades the space between planet
s in the Solar System
and in other planetary systems. It has been studied for many years in order to understand its nature, origin, and relationship to larger bodies.
In our solar system, the interplanetary dust particles not only scatter solar light (called the "zodiacal light
", which is confined to the ecliptic plane
), but also produce thermal
emission, which is the most prominent feature of the night-sky light in the 5-50 micrometer wavelength domain (Levasseur-Regourd, A.C. 1996). The grains characterizing the infrared emission near the earth
's orbit
have typical sizes of 10-100 micrometers (Backman, D., 1997). The total mass of the interplanetary dust cloud is about the mass of an asteroid
of radius 15 km (with density of about 2.5 g/cm3).
ary activity and collisions in the inner solar system, Kuiper Belt
collisions, and interstellar medium
grains (Backman, D., 1997). Indeed, one of the longest-standing controversies debated in the interplanetary dust community revolves around the relative contributions to the interplanetary dust cloud from asteroid collisions and cometary activity.
, inward Poynting-Robertson (PR) radiation drag, solar wind
pressure (with significant electromagnetic effects), sublimation, mutual collisions, and 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 100,000,000 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, 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 x 10−12 g and spiral outward from the sun into interstellar space.
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 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.
Cosmic dust
Cosmic dust is a type of dust composed of particles in space which are a few molecules to 0.1 µm in size. Cosmic dust can be further distinguished by its astronomical location; for example: intergalactic dust, interstellar dust, interplanetary dust and circumplanetary dust .In our own Solar...
(small particles floating in space) which pervades the space between planet
Planet
A planet is a celestial body orbiting a star or stellar remnant that is massive enough to be rounded by its own gravity, is not massive enough to cause thermonuclear fusion, and has cleared its neighbouring region of planetesimals.The term planet is ancient, with ties to history, science,...
s in the Solar System
Solar System
The Solar System consists of the Sun and the astronomical objects gravitationally bound in orbit around it, all of which formed from the collapse of a giant molecular cloud approximately 4.6 billion years ago. The vast majority of the system's mass is in the Sun...
and in other planetary systems. It has been studied for many years in order to understand its nature, origin, and relationship to larger bodies.
In our solar system, the interplanetary dust particles not only scatter solar light (called the "zodiacal light
Zodiacal light
Zodiacal light is a faint, roughly triangular, whitish glow seen in the night sky which appears to extend up from the vicinity of the sun along the ecliptic or zodiac. Caused by sunlight scattered by space dust in the zodiacal cloud, it is so faint that either moonlight or light pollution renders...
", which is confined to the ecliptic plane
Ecliptic
The ecliptic is the plane of the earth's orbit around the sun. In more accurate terms, it is the intersection of the celestial sphere with the ecliptic plane, which is the geometric plane containing the mean orbit of the Earth around the Sun...
), but also produce thermal
Thermal
A thermal column is a column of rising air in the lower altitudes of the Earth's atmosphere. Thermals are created by the uneven heating of the Earth's surface from solar radiation, and are an example of convection. The sun warms the ground, which in turn warms the air directly above it...
emission, which is the most prominent feature of the night-sky light in the 5-50 micrometer wavelength domain (Levasseur-Regourd, A.C. 1996). The grains characterizing the infrared emission near the earth
Earth
Earth is the third planet from the Sun, and the densest and fifth-largest of the eight planets in the Solar System. It is also the largest of the Solar System's four terrestrial planets...
's orbit
Orbit
In physics, an orbit is the gravitationally curved path of an object around a point in space, for example the orbit of a planet around the center of a star system, such as the Solar System...
have typical sizes of 10-100 micrometers (Backman, D., 1997). The total mass of the interplanetary dust cloud is about the mass of an asteroid
Asteroid
Asteroids are a class of small Solar System bodies in orbit around the Sun. They have also been called planetoids, especially the larger ones...
of radius 15 km (with density of about 2.5 g/cm3).
Sources of interplanetary dust
The sources of interplanetary dust particles (IDPs) include at least: asteroid collisions, cometComet
A comet is an icy small Solar System body that, when close enough to the Sun, displays a visible coma and sometimes also a tail. These phenomena are both due to the effects of solar radiation and the solar wind upon the nucleus of the comet...
ary activity and collisions in the inner solar system, Kuiper Belt
Kuiper belt
The Kuiper belt , sometimes called the Edgeworth–Kuiper belt, is a region of the Solar System beyond the planets extending from the orbit of Neptune to approximately 50 AU from the Sun. It is similar to the asteroid belt, although it is far larger—20 times as wide and 20 to 200 times as massive...
collisions, and interstellar medium
Interstellar medium
In astronomy, the interstellar medium is the matter that exists in the space between the star systems in a galaxy. This matter includes gas in ionic, atomic, and molecular form, dust, and cosmic rays. It fills interstellar space and blends smoothly into the surrounding intergalactic space...
grains (Backman, D., 1997). Indeed, one of the longest-standing controversies debated in the interplanetary dust community revolves around the relative contributions to the interplanetary dust cloud from asteroid collisions and cometary activity.
Dust particle life cycle
The main physical processes "affecting" (destruction or expulsion mechanisms) interplanetary dust particles are: expulsion by radiation pressureRadiation pressure
Radiation pressure is the pressure exerted upon any surface exposed to electromagnetic radiation. If absorbed, the pressure is the power flux density divided by the speed of light...
, inward Poynting-Robertson (PR) radiation drag, solar wind
Solar wind
The solar wind is a stream of charged particles ejected from the upper atmosphere of the Sun. It mostly consists of electrons and protons with energies usually between 1.5 and 10 keV. The stream of particles varies in temperature and speed over time...
pressure (with significant electromagnetic effects), sublimation, mutual collisions, and 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
Solar System
The Solar System consists of the Sun and the astronomical objects gravitationally bound in orbit around it, all of which formed from the collapse of a giant molecular cloud approximately 4.6 billion years ago. The vast majority of the system's mass is in the Sun...
. If one finds grains around a star that is older than about 100,000,000 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
Protoplanetary disk
A protoplanetary disk is a rotating circumstellar disk of dense gas surrounding a young newly formed star, a T Tauri star, or Herbig Ae/Be star...
(Backman, private communication). Therefore, 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
Interstellar medium
In astronomy, the interstellar medium is the matter that exists in the space between the star systems in a galaxy. This matter includes gas in ionic, atomic, and molecular form, dust, and cosmic rays. It fills interstellar space and blends smoothly into the surrounding intergalactic space...
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 x 10−12 g and spiral outward from the sun into interstellar space.
Interplanetary dust structures
The interplanetary dust cloud has a complex structure (Reach, W., 1997). Apart from a background density, this includes:- At least 8 dust trails -- their source is thought to be short-period comets.
- A number of dust bands, the sources of which are thought to be asteroid familiesAsteroid familyAn asteroid family is a population of asteroids that share similar proper orbital elements, such as semimajor axis, eccentricity, and orbital inclination. The members of the families are thought to be fragments of past asteroid collisions...
in the main asteroid belt. The three strongest bands arise from the Themis familyThemis familyThe Themis or Themistian Asteroid Family is a Hirayama family of asteroids found in the outer portion of the main asteroid belt, between the orbits of Mars and Jupiter. At a mean distance of 3.13 AU from the Sun, it is one of the more populous asteroid families...
, the Koronis familyKoronis family]The Koronis family is a family of asteroids in the main belt between Mars and Jupiter. They are thought to have been formed at least two billion years ago in a catastrophic collision between two larger bodies. The largest known is about in diameter. The Koronis family travels in a cluster along...
, and the Eos familyEos familyThe Eos or Eoan family is a prominent family of main belt asteroids that is believed to have formed as a result of an ancient catastrophic collision. Members of the family share similar orbits. The family is named after 221 Eos....
. Other source families include the Maria, Eunomia, and possibly the VestaVesta familyThe Vesta or Vestian family of asteroids is a large and prominent grouping of mostly V-type asteroids in the inner asteroid belt in the vicinity of 4 Vesta...
and/or HygieaHygiea familyThe Hygiea family of asteroids is a grouping of dark, carbonaceous C-type and B-type asteroids in outer main belt, the largest member of which is 10 Hygiea. About 1% of all known main belt asteroids belong to this family.-Characteristics:...
families (Reach et al. 1996). - At least 2 resonant dust rings are known (for example, the Earth-resonant dust ring, although every planet in the solar system is thought to have a resonant ring with a "wake") (Jackson and Zook, 1988, 1992) (Dermott, S.F. et al., 1994, 1997)
Collecting interplanetary dust on earth
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 D. E. Brownlee and collaborators in the 1970s using balloons and then U-2Lockheed U-2
The Lockheed U-2, nicknamed "Dragon Lady", is a single-engine, very high-altitude reconnaissance aircraft operated by the United States Air Force and previously flown by the Central Intelligence Agency . It provides day and night, very high-altitude , all-weather intelligence gathering...
aircraft.
Although some of the particles found were similar to the material in present day meteorite
collections, the nanoporous
Nanoporous
Nanoporous materials consist of a regular organic or inorganic framework supporting a regular, porous structure. Pores are by definition roughly in the nanometre range, that is between 1x10−7 and 0.2x10−9 m.Subdivisions:...
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
Noble gas
The noble gases are a group of chemical elements with very similar properties: under standard conditions, they are all odorless, colorless, monatomic gases, with very low chemical reactivity...
and
solar flare
Solar flare
A solar flare is a sudden brightening observed over the Sun surface or the solar limb, which is interpreted as a large energy release of up to 6 × 1025 joules of energy . The flare ejects clouds of electrons, ions, and atoms through the corona into space. These clouds typically reach Earth a day...
track observations.
In that context 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
Presolar grains
Presolar grains are isotopically-distinct clusters of material found in the fine-grained matrix of primitive meteorites, such as chondrites, whose differences from the surrounding meteorite suggest that they are older than the solar system...
from
meteorites, are unique sources of extraterrestrial material
Extraterrestrial materials
Most atoms on Earth came from the interstellar dust and gas from which the Sun and Solar System formed. However, in the space science community, "extraterrestrial materials" generally refers to objects now on Earth that were solidified prior to arriving on earth...
(not to mention being small astronomical objects in their own right) available for study in laboratories today.
See also
- Cosmic dustCosmic dustCosmic dust is a type of dust composed of particles in space which are a few molecules to 0.1 µm in size. Cosmic dust can be further distinguished by its astronomical location; for example: intergalactic dust, interstellar dust, interplanetary dust and circumplanetary dust .In our own Solar...
- MicrometeoroidMicrometeoroidA micrometeoroid is a tiny meteoroid; a small particle of rock in space, usually weighing less than a gram. A micrometeor or micrometeorite is such a particle that enters the Earth's atmosphere or falls to Earth.-Scientific interest:...
- Atmospheric entry
- Zodiacal dustZodiacal dustThe Zodiacal dust cloud is visible as a diffuse glow, known as the zodiacal light, that stretches along the zodiac, and is best seen just after sunset and before sunrise in spring and autumn when the zodiac is at a steep angle to the horizon....
- Interplanetary space - Interplanetary mediumInterplanetary mediumThe interplanetary medium is the material which fills the solar system and through which all the larger solar system bodies such as planets, asteroids and comets move.-Composition and physical characteristics:...
- interplanetary dust - Interstellar spaceInterstellar SpaceInterstellar Space was one of the final studio albums recorded by the saxophonist John Coltrane before his death in 1967, originally-released posthumously by Impulse! Records on LP in 1974.-Composition:...
- Interstellar mediumInterstellar mediumIn astronomy, the interstellar medium is the matter that exists in the space between the star systems in a galaxy. This matter includes gas in ionic, atomic, and molecular form, dust, and cosmic rays. It fills interstellar space and blends smoothly into the surrounding intergalactic space...
- interstellar dust - Intergalactic space - Intergalactic medium - Intergalactic dustIntergalactic dustIntergalactic dust is cosmic dust in between galaxies in intergalactic space. Evidence for intergalactic dust has been suggested as early as 1949, and study of it grew throughout the late 20th century. There are large variations in the distribution of intergalactic dust...