The interplanetary dust cloud, or zodiacal cloud (as the source of the

zodiacal light The zodiacal light (also called false dawn when seen before sunrise) is a faint glow of diffuse sunlight scattered by interplanetary dust. Brighter around the Sun, it appears in a particularly dark night sky to extend from the Sun's direct ...

), consists of

cosmic dust Cosmic dustalso called extraterrestrial dust, space dust, or star dustis dust that occurs in outer space or has fallen onto Earth. Most cosmic dust particles measure between a few molecules and , such as micrometeoroids (30 μm). Cosmic dust can ...

(small

particles In the physical sciences, a particle (or corpuscle in older texts) is a small localized object which can be described by several physical or chemical properties, such as volume, density, or mass. They vary greatly in size or quantity, from s ...

floating in outer space) that pervades the space between

planet A planet is a large, Hydrostatic equilibrium, rounded Astronomical object, astronomical body that is generally required to be in orbit around a star, stellar remnant, or brown dwarf, and is not one itself. The Solar System has eight planets b ...

s within

planetary system A planetary system is a set of gravity, gravitationally bound non-stellar Astronomical object, bodies in or out of orbit around a star or star system. Generally speaking, systems with one or more planets constitute a planetary system, although ...

s, such as the

Solar System The Solar SystemCapitalization of the name varies. The International Astronomical Union, the authoritative body regarding astronomical nomenclature, specifies capitalizing the names of all individual astronomical objects but uses mixed "Sola ...

. 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 In physics, scattering is a wide range of physical processes where moving particles or radiation of some form, such as light or sound, are forced to deviate from a straight trajectory by localized non-uniformities (including particles and radiat ...

sunlight Sunlight is the portion of the electromagnetic radiation which is emitted by the Sun (i.e. solar radiation) and received by the Earth, in particular the visible spectrum, visible light perceptible to the human eye as well as invisible infrare ...

and in emitting

thermal radiation Thermal radiation is electromagnetic radiation emitted by the thermal motion of particles in matter. All matter with a temperature greater than absolute zero emits thermal radiation. The emission of energy arises from a combination of electro ...

, which is the most prominent feature of the

night sky The night sky is the nighttime appearance of celestial objects like stars, planets, and the Moon, which are visible in a clear sky between sunset and sunrise, when the Sun is below the horizon. Natural light sources in a night sky include moonlig ...

's radiation, with wavelengths ranging 5–50 μm. The

particle size Particle size is a notion introduced for comparing dimensions of solid particles ('' flecks''), liquid particles ('' droplets''), or gaseous particles ('' bubbles''). The notion of particle size applies to particles in colloids, in ecology, in ...

s of grains characterizing the

infrared Infrared (IR; sometimes called infrared light) is electromagnetic radiation (EMR) with wavelengths longer than that of visible light but shorter than microwaves. The infrared spectral band begins with the waves that are just longer than those ...

emission near

Earth's orbit Earth orbits the Sun at an astronomical unit, average distance of , or 8.317 light-second, light-minutes, in a retrograde and prograde motion, counterclockwise direction as viewed from above the Northern Hemisphere. One complete orbit takes & ...

typically range 10–100 μm. Microscopic impact craters on lunar rocks returned by the

Apollo Program The Apollo program, also known as Project Apollo, was the United States human spaceflight program led by NASA, which Moon landing, landed the first humans on the Moon in 1969. Apollo followed Project Mercury that put the first Americans in sp ...

revealed the size distribution of

particles bombarding the lunar surface. The ’’Grün’’ distribution of interplanetary dust at 1 AU, describes the flux of

from nm to mm sizes at 1 AU. The total mass of the interplanetary dust cloud is approximately , or the mass of an

asteroid An asteroid is a minor planet—an object larger than a meteoroid that is neither a planet nor an identified comet—that orbits within the Solar System#Inner Solar System, inner Solar System or is co-orbital with Jupiter (Trojan asteroids). As ...

of radius 15 km (with density of about 2.5 g/cm³). Straddling the

zodiac The zodiac is a belt-shaped region of the sky that extends approximately 8° north and south celestial latitude of the ecliptic – the apparent path of the Sun across the celestial sphere over the course of the year. Within this zodiac ...

along the

ecliptic The ecliptic or ecliptic plane is the orbital plane of Earth's orbit, Earth around the Sun. It was a central concept in a number of ancient sciences, providing the framework for key measurements in astronomy, astrology and calendar-making. Fr ...

, this dust cloud is visible as the zodiacal light in a moonless and naturally dark sky and is best seen sunward during astronomical

twilight Twilight is daylight illumination produced by diffuse sky radiation when the Sun is below the horizon as sunlight from the upper atmosphere is scattered in a way that illuminates both the Earth's lower atmosphere and also the Earth's surf ...

. The '' Pioneer'' spacecraft observations in the 1970s linked the

with the interplanetary dust cloud in the Solar System. Also, the VBSDC instrument on the ''

New Horizons ''New Horizons'' is an Interplanetary spaceflight, interplanetary space probe launched as a part of NASA's New Frontiers program. Engineered by the Johns Hopkins University Applied Physics Laboratory (APL) and the Southwest Research Institut ...

'' probe was designed to detect impacts of the dust from the zodiacal cloud in the Solar System.

Origin

The sources of interplanetary dust particles (IDPs) include at least: asteroid collisions,

comet A comet is an icy, small Solar System body that warms and begins to release gases when passing close to the Sun, a process called outgassing. This produces an extended, gravitationally unbound atmosphere or Coma (cometary), coma surrounding ...

ary activity and collisions in the inner Solar System,

Kuiper belt The Kuiper belt ( ) is a circumstellar disc in the outer Solar System, extending from the orbit of Neptune at 30 astronomical units (AU) to approximately 50 AU from the Sun. It is similar to the asteroid belt, but is far larger—20 times ...

collisions, and

interstellar medium The interstellar medium (ISM) is the matter and radiation that exists in the outer space, space between the star systems in a galaxy. This matter includes gas in ionic, atomic, and molecular form, as well as cosmic dust, dust and cosmic rays. It f ...

grains (Backman, D., 1997). The origins of 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 A dust storm, also called a sandstorm, is a meteorological phenomenon common in arid and semi-arid regions. Dust storms arise when a gust front or other strong wind blows loose sand and dirt from a dry surface. Fine particles are transported ...

may be responsible for the zodiacal cloud's formation.

Life cycle of a particle

The main physical processes "affecting" (destruction or expulsion mechanisms) interplanetary dust particles are: expulsion by

radiation pressure Radiation pressure (also known as light pressure) is mechanical pressure exerted upon a surface due to the exchange of momentum between the object and the electromagnetic field. This includes the momentum of light or electromagnetic radiation of ...

, inward Poynting-Robertson (PR) radiation drag,

solar wind The solar wind is a stream of charged particles released from the Sun's outermost atmospheric layer, the Stellar corona, corona. This Plasma (physics), plasma mostly consists of electrons, protons and alpha particles with kinetic energy betwee ...

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 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 A protoplanetary disk is a rotating circumstellar disc of dense gas and dust surrounding a young newly formed star, a T Tauri star, or Herbig Ae/Be star. The protoplanetary disk may not be considered an accretion disk; while the two are sim ...

(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

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 × 10⁻¹² g and are pushed outward from the Sun into interstellar space.

Cloud 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 families in the main asteroid belt. The three strongest bands arise from the

Themis family The Themis family (''adj. Themistian''; ) is a family of carbonaceous asteroids located in the outer portion of the asteroid belt, at a mean distance of 3.13 AU from the Sun. It is one of the largest families with over 4700 known members, and c ...

, the

Koronis family ] The Koronis or Koronian family (), also known as the Lacrimosa family, is a very large asteroid family of S-type asteroid, stony asteroids, located in the Kirkwood gap, outer region of the asteroid belt. They are thought to have been formed at l ...

, and the

Eos family The Eos family (''adj. Eoan'' ; ) is a very large asteroid family located in the outer region of the asteroid belt. This family of K-type asteroids is believed to have formed as a result of an ancient catastrophic collision. The family's parent b ...

. Other source families include the Maria, Eunomia, and possibly the Vesta and/or Hygiea 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)

Rings of dust

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 the remains of the Solar System's circumstellar disc, out of which its proto-planetary disc and then itself, the Solar

, formed.

Dust collection on Earth

In 1951,

Fred Whipple Fred Lawrence Whipple (November 5, 1906 – August 30, 2004) was an American astronomer, who worked at the Harvard College Observatory for more than 70 years. Among his achievements were asteroid and comet discoveries, the " dirty snowball" hy ...

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 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 The noble gases (historically the inert gases, sometimes referred to as aerogens) are the members of Group (periodic table), group 18 of the periodic table: helium (He), neon (Ne), argon (Ar), krypton (Kr), xenon (Xe), radon (Rn) and, in some ...

and

solar flare A solar flare is a relatively intense, localized emission of electromagnetic radiation in the Sun's atmosphere. Flares occur in active regions and are often, but not always, accompanied by coronal mass ejections, solar particle events, and ot ...

track observations. In that context a program for atmospheric collection and curation of these particles was developed at

Johnson Space Center The Lyndon B. Johnson Space Center (JSC) is NASA's center for human spaceflight in Houston, Texas (originally named the Manned Spacecraft Center), where human spaceflight training, research, and flight controller, flight control are conducted. ...

in Texas. This stratospheric micrometeorite collection, along with

presolar grains Presolar grains are interstellar solid matter in the form of tiny solid grains that originated at a time before the Sun was formed. Presolar grains formed within outflowing and cooling gases from earlier presolar stars. The study of presolar grai ...

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.

Experiments

Spacecraft that have carried dust detectors include ''

Helios In ancient Greek religion and Greek mythology, mythology, Helios (; ; Homeric Greek: ) is the god who personification, personifies the Sun. His name is also Latinized as Helius, and he is often given the epithets Hyperion ("the one above") an ...

'', ''

Pioneer 10 ''Pioneer 10'' (originally designated Pioneer F) is a NASA space probe launched in 1972 that completed the first mission to the planet Jupiter. ''Pioneer 10'' became the first of five artificial objects to achieve the escape velocity needed ...

'', ''

Pioneer 11 ''Pioneer 11'' (also known as ''Pioneer G'') is a NASA robotic space probe launched on April 5, 1973, to study the asteroid belt, the environment around Jupiter and Saturn, the solar wind, and cosmic rays. It was the first probe to Exploration ...

'', '' Ulysses'' (heliocentric orbit out to the distance of Jupiter), ''

Galileo Galileo di Vincenzo Bonaiuti de' Galilei (15 February 1564 – 8 January 1642), commonly referred to as Galileo Galilei ( , , ) or mononymously as Galileo, was an Italian astronomer, physicist and engineer, sometimes described as a poly ...

'' (Jupiter Orbiter), '' Cassini'' (Saturn orbiter), and ''

'' (see Venetia Burney Student Dust Counter).

Obscuring effect

The Solar interplanetary dust cloud obscures the

extragalactic background light The diffuse extragalactic background light (EBL) is all the accumulated radiation in the universe due to star formation processes, plus a contribution from active galactic nuclei (AGNs). This radiation covers almost all wavelengths of the electrom ...

, making observations of it from the Inner Solar System very limited.

Major Review Collections

Collections of review articles on various aspects of interplanetary dust and related fields appeared in 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 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 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 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.