# Dominant group/Planetary science

Within planetary science, in theory, there may be at least two meanings of dominant group: (1) a dominant group of objects, sources, and entities, or (2) a dominant group in some way associated with objects, sources, or entities, or with planetary science itself. Emphasis may be on an object rather than by association.
In the first sense, some such objects with respect to the Moon, for example, consist of a lunar boulder, soil, and terrain. The second sense seems to use the Moon only as a back drop for investigations on Earth, for example, the effects of lunar tides or the Moon Treaty. Or, may refer to groups who influence the field of planetary science. The first is more substantive, the second more subjective.

## Dominant groups

Examples from primary sources are to be used to prove or disprove each hypothesis. These can be collected per subject or in general.
* Accident hypothesis: dominant group is an accident of whatever processes are operating.
* Artifact hypothesis: dominant group may be an artifact of human endeavor or may have preceded humanity.
* Association hypothesis: dominant group is associated in some way with the original research.
* Bad group hypothesis: dominant group is the group that engages in discrimination, abuse, punishment, and additional criminal activity against other groups. It often has an unfair advantage and uses it to express monopolistic practices.
* Control group hypothesis: there is a control group that can be used to study dominant group.
* Entity hypothesis: dominant group is an entity within each field where a primary author of original research uses the term.
* Evolution hypothesis: dominant group is a product of evolutionary processes, such groups are the evolutionary process, produce evolutionary processes, or are independent of evolutionary processes.
* Identifier hypothesis: dominant group is an identifier used by primary source authors of original research to identify an observation in the process of analysis.
* Importance hypothesis: dominant group signifies original research results that usually need to be explained by theory and interpretation of experiments.
* Indicator hypothesis: dominant group may be an indicator of something as yet not understood by the primary author of original research.
* Influence hypothesis: dominant group is included in a primary source article containing original research to indicate influence or an influential phenomenon.
* Interest hypothesis: dominant group is a theoretical entity used by scholarly authors of primary sources for phenomena of interest.
* Metadefinition hypothesis: all uses of dominant group by all primary source authors of original research are included in the metadefinition for dominant group.
* Null hypothesis: there is no significant or special meaning of dominant group in any sentence or figure caption in any refereed journal article.
* Object hypothesis: dominant group is an object within each field where a primary author of original research uses the term.
* Obvious hypothesis: the only meaning of dominant group is the one found in Mosby's Medical Dictionary.
* Original research hypothesis: dominant group is included in a primary source article by the author to indicate that the article contains original research.
* Primordial hypothesis: dominant group is a primordial concept inherent to humans such that every language or other form of communication no matter how old or whether extinct, on the verge of extinction, or not, has at least a synonym for dominant group.
* Purpose hypothesis: dominant group is written into articles by authors for a purpose.
* Regional hypothesis: dominant group, when it occurs, is only a manifestation of the limitations within a region. Variation of those limitations may result in the loss of a dominant group with the eventual appearance of a new one or none at all.
* Source hypothesis: dominant group is a source within each field where a primary author of original research uses the term.
* Term hypothesis: dominant group is a significant term that may require a 'rigorous definition' or application and verification of an empirical definition.

## Sciences

A systematically organized body of knowledge on a particular subject is often thought of as a science. The collection of such bodies of knowledge also systematically organized likely constitutes the sciences.
A more archaic meaning is knowledge of any kind whether found through the use of the scientific method or not.
Perhaps nothing symbolizes the sciences more than astronaut Buzz Aldrin, lunar module pilot, walking on the surface of the Moon near the leg of the Lunar Module (LM) "Eagle" during the Apollo 11 extravehicular activity (EVA). Astronaut Neil A. Armstrong, commander, took this photograph with a 70 mm lunar surface camera. While astronauts Armstrong and Aldrin descended in the Lunar Module (LM) "Eagle" to explore the Sea of Tranquility region of the Moon, astronaut Michael Collins, command module pilot, remained with the Command and Service Modules (CSM) "Columbia" in lunar orbit.

## Planetary

Planetary may refer to objects in orbit around a star, or objects that wander around the sky, especially at night. The latter such objects may be gaseous objects, rocky objects, or plasma objects, even liquid objects.

## Rocky objects

"Silicates are the dominant group minerals in the Earth's crust."
"T$_c$s are dominated by the volumetrically dominant Group A grains in the pillow interior and are generally between 130 and 190°C (sub-samples d–l at depths of 1.5 to 6.2 cm from the rim"
Much of the use of dominant group relative to the Earth (rocky object) is described in dominant group/Geology.

## Meteors

"The distribution of photographic meteors in iron, stony, and porous meteors is given in this paper". "[A]mong all the 217 meteors for which we know the beginning there are 70 iron meteors, i. e. about 32 p. c., and 147 stony meteors, i. e. 68 p. c." The meteor streams: Perseids, Geminids, Taurids, Lyrids, κ Cygnids and Virginids, are quite stony.
"The dominant group in all cases are stony meteors."

## Meteorites

Roughly three-quarters of all Martian meteorites can be classified as shergottites. "[T]he most frequent type of rock (basaltic lithologies) among all known Martian meteorites is the basaltic shergottites."
"The dominant group of Martian meteorites, shergottites, are divided into two subgroups consisting of basalts and lherzolites.
"The highly refractory elements ... are followed by the dominant group of refractory lithophile elements (Si, P, and the alkali-earth and transition elements typical of chondrules, which condense down to 1,300 K."
Micrometeorite is often abbreviated as MM. Most MMs are broadly chondritic in composition, meaning "that major elemental abundance ratios are within about 50% of those observed in carbonaceous chondrites." Some MMs are chondrites, (basaltic) howardite, eucrite, and diogenite (HED) meteorites or Martian basalts, but not lunar samples. "[T]he comparative mechanical weakness of carbonaceous precursor materials tends to encourage spherule formation." From the number of different asteroidal precursors, the approximate fraction in MMs is 70 % carbonaceous. "[T]he carbonaceous material [is] known from observation to dominate the terrestrial MM flux." The "H, L, and E chondritic compositions" are "dominant among meteorites but rare among micrometeorites."
"Ureilites occur about half as often as eucrites (Krot et al. 2003), are relatively friable, have less a wide range of cosmic-ray exposure ages including two less than 1 Myr, and, like the dominant group of MM precursors, contain carbon."
"These particles belong to the dominant group of micrometeorites which are related to the CM chondrites and show a relatively low degree of PAH alkylation."

## Meteoroids

A meteoroid is a suggested term for a sand- to boulder-sized particle of debris in the Solar System. The visible path of a meteoroid that enters the Earth's atmosphere (or another body's) atmosphere is called a meteor, or colloquially a shooting star or falling star. If a meteoroid reaches the ground and survives impact, then it is called a meteorite.
"A meteoroid is a sand- to boulder-sized particle of debris in the Solar System."
"The silicate spheres are the most dominant group."

## Moon

The Apollo 17 highland samples are classified into groups according to proportions of meteoritic iridium (Ir), gold (Au), and germanium (Ge) by atomic concentration. Ni is the elemental symbol for nickel and Re is the elemental symbol for rhenium.
"It is quite distinct from the Group 2 component (Ir/Au - 0.46-0.54) that dominates at the Apollo 17 site." "[I]f the dominant Group 2 component at Apollo 17 comes from the Serenitatis projectile, then the component in Boulder 2-1 must come from another projectile, older or younger." "Sixteen samples of Boulder 1 from Station 2 at the Apollo 17 site were analyzed". Remaining Apollo 17 data other than from Boulder 2-1 (Boulder 1 from Station 2) are included.
"Nine out of 10 well-characterized Apollo 17 breccia matrices fall into Group 2, and this includes both the blue-grey breccias which are the dominant rock type at this site".
KREEP, an acronym built from the letters K (the atomic symbol for potassium), REE (Rare Earth Elements) and P (for phosphorus), is a geochemical component of some lunar impact melt breccia and basalt rocks.
"Glasses from Apollo 11, 12, 14, and 15 soil samples have been grouped on the basis of their chemistry". More than half of the Apollo 14 soil glasses belong to the group of glasses that relate to KREEP-type basalts. "KREEP-type glasses in the Apollo 15 soil samples closely resemble the ones in the Apollo 14 samples". Of 399 glasses analyzed, the single largest group of glasses, numbering 140, relate to KREEP-type basalts.
"Because KREEP glasses are the dominant group at the Fra Mauro sampling site and because the Fra Mauro formation is considered part of the Imbrian ejecta blanket, KREEP basalts appear to have been part of the lunar crust prior to formation of the Imbrium Basin."
"These glasses are the dominant group in soil 60501 and also in 61221 if the pure feldspar glasses are discounted."
The lunar impact glasses from the Apollo 14 landing site show significant variation and hint at the existence of multiple terrains of differing compositions near the landing site. Gamma-ray spectrometer observations show a high concentration of potassium, rare Earth element, and phosphorus (KREEP) around and at the Apollo 14 landing site. "Lunar impact glasses record the composition, in refractory element ratios, of the material from which they were formed." By far the most populous group of Apollo 14 impact glasses by compositional distribution on a ternary diagram of aluminum (Al), iron (Fe), and titanium (Ti), is a diffuse cluster of glasses elevated in KREEP called the "high-K Fra Mauro basalt" (HKFM).
"The glass data from Apollo 14 soil 14259,624 show that the bulk composition of the deposit at the site is dominated by high-K Fra Mauro ‘‘basalt."
"In addition to that dominant group of glasses, we find smaller groups of more feldspathic glasses, in particular a tight cluster of ‘‘highland basalt’’ glasses, similar to glasses and soils found at the Apollo 16 site and in lunar meteorites (Figure 5 and Table 2)."

## Interplanetary dust

"It is found that near 1 AU, the dominant group of the local geometrical cross section changes." Approximately 80 % of interplanetary dust is cometary at R ~ 0.8 AU.

## Mars

The "enigmatic linear and curvilinear features (hereinafter referred to as LCFs) that in general are visible as thin dark, or rarely white lines in satellite images of the Martian surface ... are in such abundance that they are even visible in Viking images."
"The color code indicates the most dominant group of LCFs in the image."

## Asteroids

"Asteroids in particularly large classes tend to be broken into subgroups with the first letter denoting the dominant group and the succeeding letters denoting less prominent spectral affinities or subgroups."
"The recent investigation of the orbital distribution of Centaurs (Emel’yanenko et al., 2005) showed that there are two dynamically distinct classes of Centaurs, a dominant group with semimajor axes a > 60 AU and a minority group with a < 60 AU." "[T]he intrinsic number of such objects is roughly an order of magnitude greater than that for a<60 AU".
"From the dominant group, the asteroids evolve to intersect the Earth's orbit on a median time scale of about 60 Myr." "The MB group is the most numerous group of MCs. ... 50 % of the MB Mars-crossers [MCs] become ECs within 59.9 Myr and [this] contribution ... dominates the production of ECs". MB denotes the main belt of asteroids. EC denotes Earth-crossing.

## Liquid objects

"Why are their essays and books about the endangered earth so monological -- that is, a conversation of a dominant group talking to itself?"
Much of the use of dominant group relative to the Earth (liquid object) is described in dominant group/Geography.

## Gaseous objects

Searching with Google scholar has been unsuccessful in finding any use of dominant group and the gaseous objects Jupiter, Neptune, Saturn, or Uranus. A search using "gaseous planets", "gas planets", or "giant planets" with dominant group produced no results. Dominant group is associated with comets and asteroids, in turn, near to or originating from influences by these planets.
Dominant group does show up with respect to these gaseous objects in mythology.
Much of the use of dominant group relative to the Earth (gaseous object) is described in dominant group/Atmospheric science.

## Plasma objects

A magnetohydrodynamics (MHD) and chemical comet-coma model is applied to describe and analyze the plasma flow, magnetic field, and ion abundances in Comet Halley. A comparison of model results is made with the data from the Giotto mission.
"In the second dominant group of ions we generally see more discrepancies in the model and the HIS data".
The principal application of the dominant group concept is to the ion density measurements at or within 1500 km of the comet nucleus, where "the model abundances for the light ions, up to 21 amu, are in very good agreement with the 1500 km observations."
The comparison between model and measurements "generally becomes worse as one considers higher molecular masses and greater distance from the [comet] nucleus."
"In fact, observations of the volatiles in 9P/Tempel 1 indicate that the abundance ratios for most species in the ejecta are in the range of those found for the dominant group of Oort Cloud comets (Mumma et al. 2005), implying that many short-period comets maintain the components they had on leaving the trans-Neptunian region at 1 m of depth from the surface, even after numerous perihelion passages."
"In particular, the O isotopic ratios of the dominant Group 1 grains (Figure 4) are consistent both with spectroscopic observations of O-rich red giants and AGB stars (Harris & Lambert 1984) and with model calculations of dredge-up processes in these stars (labeled curve in Figure 4) (Boothroyd & Sackmann 1999, Dearborn 1992, El Eid 1994)."
"The dominant group of detectable eclipsing binaries consists of two detached main-sequence stars." "In the case of survey model 1 and a flat initial mass ratio distribution, this subgroup of systems accounts for 60% of the population of detectable eclipsing binaries." "In this exploratory study we used the BiSEPS binary population synthesis code to estimate the number of eclipsing binaries and single stars detectable in the Galactic disc by an idealised Super-WASP exoplanet transit survey."

## Hypotheses

* A dominant group with respect to planetary science is likely associated with the concept of a planet or the science of planets.