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Planetary science
Planetary science
or, more rarely, planetology, is the scientific study of planets (including Earth), moons, and planetary systems (in particular those of the Solar System) and the processes that form them. It studies objects ranging in size from micrometeoroids to gas giants, aiming to determine their composition, dynamics, formation, interrelations and history. It is a strongly interdisciplinary field, originally growing from astronomy and earth science,[1] but which now incorporates many disciplines, including planetary geology (together with geochemistry and geophysics), cosmochemistry, atmospheric science, oceanography, hydrology, theoretical planetary science, glaciology, and exoplanetology.[1] Allied disciplines include space physics, when concerned with the effects of the Sun
Sun
on the bodies of the Solar System, and astrobiology. There are interrelated observational and theoretical branches of planetary science. Observational research can involve a combination of space exploration, predominantly with robotic spacecraft missions using remote sensing, and comparative, experimental work in Earth-based laboratories. The theoretical component involves considerable computer simulation and mathematical modelling. Planetary scientists are generally located in the astronomy and physics or Earth
Earth
sciences departments of universities or research centres, though there are several purely planetary science institutes worldwide. There are several major conferences each year, and a wide range of peer-reviewed journals. In the case of some exclusive planetary scientists, many of whom are in relation to the study of dark matter, they will seek a private research centre and often initiate partnership research tasks.

Contents

1 History 2 Disciplines

2.1 Planetary astronomy 2.2 Planetary geology

2.2.1 Geomorphology 2.2.2 Cosmochemistry, geochemistry and petrology 2.2.3 Geophysics

2.3 Atmospheric science

3 Comparative planetary science 4 Professional activity

4.1 Journals 4.2 Professional bodies 4.3 Major conferences 4.4 Major institutions

4.4.1 National space agencies 4.4.2 Other institutions

5 Basic concepts 6 See also 7 References 8 Further reading 9 External links

History[edit] The history of planetary science may be said to have begun with the Ancient Greek philosopher Democritus, who is reported by Hippolytus as saying

The ordered worlds are boundless and differ in size, and that in some there is neither sun nor moon, but that in others, both are greater than with us, and yet with others more in number. And that the intervals between the ordered worlds are unequal, here more and there less, and that some increase, others flourish and others decay, and here they come into being and there they are eclipsed. But that they are destroyed by colliding with one another. And that some ordered worlds are bare of animals and plants and all water.[2]

In more modern times, planetary science began in astronomy, from studies of the unresolved planets. In this sense, the original planetary astronomer would be Galileo, who discovered the four largest moons of Jupiter, the mountains on the Moon, and first observed the rings of Saturn, all objects of intense later study. Galileo's study of the lunar mountains in 1609 also began the study of extraterrestrial landscapes: his observation "that the Moon
Moon
certainly does not possess a smooth and polished surface" suggested that it and other worlds might appear "just like the face of the Earth
Earth
itself".[3] Advances in telescope construction and instrumental resolution gradually allowed increased identification of the atmospheric and surface details of the planets. The Moon
Moon
was initially the most heavily studied, as it always exhibited details on its surface, due to its proximity to the Earth, and the technological improvements gradually produced more detailed lunar geological knowledge. In this scientific process, the main instruments were astronomical optical telescopes (and later radio telescopes) and finally robotic exploratory spacecraft. The Solar System
Solar System
has now been relatively well-studied, and a good overall understanding of the formation and evolution of this planetary system exists. However, there are large numbers of unsolved questions,[4] and the rate of new discoveries is very high, partly due to the large number of interplanetary spacecraft currently exploring the Solar System. Disciplines[edit] Planetary astronomy[edit] This is both an observational and a theoretical science. Observational researchers are predominantly concerned with the study of the small bodies of the Solar System: those that are observed by telescopes, both optical and radio, so that characteristics of these bodies such as shape, spin, surface materials and weathering are determined, and the history of their formation and evolution can be understood. Theoretical planetary astronomy is concerned with dynamics: the application of the principles of celestial mechanics to the Solar System and extrasolar planetary systems. Planetary geology[edit] Main article: Planetary geology See also: Geology of solar terrestrial planets
Geology of solar terrestrial planets
and Icy moon The best known research topics of planetary geology deal with the planetary bodies in the near vicinity of the Earth: the Moon, and the two neighbouring planets: Venus
Venus
and Mars. Of these, the Moon
Moon
was studied first, using methods developed earlier on the Earth. Geomorphology[edit] Main article: Geomorphology Geomorphology
Geomorphology
studies the features on planetary surfaces and reconstructs the history of their formation, inferring the physical processes that acted on the surface. Planetary geomorphology includes the study of several classes of surface features:

Impact features (multi-ringed basins, craters) Volcanic and tectonic features (lava flows, fissures, rilles) Space weathering
Space weathering
- erosional effects generated by the harsh environment of space (continuous micro meteorite bombardment, high-energy particle rain, impact gardening). For example, the thin dust cover on the surface of the lunar regolith is a result of micro meteorite bombardment. Hydrological features: the liquid involved can range from water to hydrocarbon and ammonia, depending on the location within the Solar System.

The history of a planetary surface can be deciphered by mapping features from top to bottom according to their deposition sequence, as first determined on terrestrial strata by Nicolas Steno. For example, stratigraphic mapping prepared the Apollo astronauts for the field geology they would encounter on their lunar missions. Overlapping sequences were identified on images taken by the Lunar Orbiter program, and these were used to prepare a lunar stratigraphic column and geological map of the Moon. Further information: Geology of the Moon Cosmochemistry, geochemistry and petrology[edit] Main articles: Cosmochemistry, Geochemistry, and Petrology One of the main problems when generating hypotheses on the formation and evolution of objects in the Solar System
Solar System
is the lack of samples that can be analysed in the laboratory, where a large suite of tools are available and the full body of knowledge derived from terrestrial geology can be brought to bear. Fortunately, direct samples from the Moon, asteroids and Mars
Mars
are present on Earth, removed from their parent bodies and delivered as meteorites. Some of these have suffered contamination from the oxidising effect of Earth's atmosphere
Earth's atmosphere
and the infiltration of the biosphere, but those meteorites collected in the last few decades from Antarctica
Antarctica
are almost entirely pristine. The different types of meteorites that originate from the asteroid belt cover almost all parts of the structure of differentiated bodies: meteorites even exist that come from the core-mantle boundary (pallasites). The combination of geochemistry and observational astronomy has also made it possible to trace the HED meteorites back to a specific asteroid in the main belt, 4 Vesta. The comparatively few known Martian meteorites
Martian meteorites
have provided insight into the geochemical composition of the Martian crust, although the unavoidable lack of information about their points of origin on the diverse Martian surface has meant that they do not provide more detailed constraints on theories of the evolution of the Martian lithosphere.[5] As of July 24, 2013 65 samples of Martian meteorites have been discovered on Earth. Many were found in either Antarctica
Antarctica
or the Sahara Desert. During the Apollo era, in the Apollo program, 384 kilograms of lunar samples were collected and transported to the Earth, and 3 Soviet Luna robots also delivered regolith samples from the Moon. These samples provide the most comprehensive record of the composition of any Solar System body beside the Earth. The numbers of lunar meteorites are growing quickly in the last few years –[6] as of April 2008 there are 54 meteorites that have been officially classified as lunar. Eleven of these are from the US Antarctic meteorite collection, 6 are from the Japanese Antarctic meteorite collection, and the other 37 are from hot desert localities in Africa, Australia, and the Middle East. The total mass of recognized lunar meteorites is close to 50 kg. Geophysics[edit] Main articles: Geophysics
Geophysics
and Space physics Space probes made it possible to collect data in not only the visible light region, but in other areas of the electromagnetic spectrum. The planets can be characterized by their force fields: gravity and their magnetic fields, which are studied through geophysics and space physics. Measuring the changes in acceleration experienced by spacecraft as they orbit has allowed fine details of the gravity fields of the planets to be mapped. For example, in the 1970s, the gravity field disturbances above lunar maria were measured through lunar orbiters, which led to the discovery of concentrations of mass, mascons, beneath the Imbrium, Serenitatis, Crisium, Nectaris and Humorum basins.

The solar wind is deflected by the magnetosphere (not to scale)

If a planet's magnetic field is sufficiently strong, its interaction with the solar wind forms a magnetosphere around a planet. Early space probes discovered the gross dimensions of the terrestrial magnetic field, which extends about 10 Earth
Earth
radii towards the Sun. The solar wind, a stream of charged particles, streams out and around the terrestrial magnetic field, and continues behind the magnetic tail, hundreds of Earth
Earth
radii downstream. Inside the magnetosphere, there are relatively dense regions of solar wind particles, the Van Allen radiation belts. Geophysics
Geophysics
includes seismology and tectonophysics, geophysical fluid dynamics, mineral physics, geodynamics, mathematical geophysics, and geophysical surveying. Geodesy, also called geodetics, deals with the measurement and representation of the planets of the Solar System, their gravitational fields and geodynamic phenomena (polar motion in three-dimensional, time-varying space. The science of geodesy has elements of both astrophysics and planetary sciences. The shape of the Earth
Earth
is to a large extent the result of its rotation, which causes its equatorial bulge, and the competition of geologic processes such as the collision of plates and of vulcanism, resisted by the Earth's gravity field. These principles can be applied to the solid surface of Earth (orogeny; Few mountains are higher than 10 km (6 mi), few deep sea trenches deeper than that because quite simply, a mountain as tall as, for example, 15 km (9 mi), would develop so much pressure at its base, due to gravity, that the rock there would become plastic, and the mountain would slump back to a height of roughly 10 km (6 mi) in a geologically insignificant time. Some or all of these geologic principles can be applied to other planets besides Earth. For instance on Mars, whose surface gravity is much less, the largest volcano, Olympus Mons, is 27 km (17 mi) high at its peak, a height that could not be maintained on Earth. The Earth
Earth
geoid is essentially the figure of the Earth
Earth
abstracted from its topographic features. Therefore, the Mars
Mars
geoid is essentially the figure of Mars
Mars
abstracted from its topographic features. Surveying
Surveying
and mapping are two important fields of application of geodesy. Atmospheric science[edit] Main articles: Atmospheric science
Atmospheric science
and Global climate model

Cloud bands clearly visible on Jupiter.

The atmosphere is an important transitional zone between the solid planetary surface and the higher rarefied ionizing and radiation belts. Not all planets have atmospheres: their existence depends on the mass of the planet, and the planet's distance from the Sun — too distant and frozen atmospheres occur. Besides the four gas giant planets, almost all of the terrestrial planets (Earth, Venus, and Mars) have significant atmospheres. Two moons have significant atmospheres: Saturn's moon Titan and Neptune's moon Triton. A tenuous atmosphere exists around Mercury. The effects of the rotation rate of a planet about its axis can be seen in atmospheric streams and currents. Seen from space, these features show as bands and eddies in the cloud system, and are particularly visible on Jupiter
Jupiter
and Saturn. Comparative planetary science[edit] Main article: Comparative planetary science Planetary science
Planetary science
frequently makes use of the method of comparison to give a greater understanding of the object of study. This can involve comparing the dense atmospheres of Earth
Earth
and Saturn's moon Titan, the evolution of outer Solar System
Solar System
objects at different distances from the Sun, or the geomorphology of the surfaces of the terrestrial planets, to give only a few examples. The main comparison that can be made is to features on the Earth, as it is much more accessible and allows a much greater range of measurements to be made. Earth
Earth
analogue studies are particularly common in planetary geology, geomorphology, and also in atmospheric science. Professional activity[edit] Journals[edit]

Earth
Earth
and Planetary Science Letters Earth, Moon, and Planets Geochimica et Cosmochimica Acta Icarus Journal of Geophysical Research—Planets Meteoritics and Planetary Science Planetary and Space Science

Professional bodies[edit]

Division for Planetary Sciences (DPS) of the American Astronomical Society American Geophysical Union Meteoritical Society Europlanet

Major conferences[edit]

Lunar and Planetary Science Conference
Lunar and Planetary Science Conference
(LPSC), organized by the Lunar and Planetary Institute in Houston. Held annually since 1970, occurs in March. Division for Planetary Sciences (DPS) meeting held annually since 1970 at a different location each year, predominantly within the mainland US. Occurs around October. American Geophysical Union
American Geophysical Union
(AGU) annual Fall meeting in December in San Francisco. American Geophysical Union
American Geophysical Union
(AGU) Joint Assembly (co-sponsored with other societies) in April–May, in various locations around the world. Meteoritical Society annual meeting, held during the Northern Hemisphere summer, generally alternating between North America and Europe. European Planetary Science Congress (EPSC), held annually around September at a location within Europe.

Smaller workshops and conferences on particular fields occur worldwide throughout the year. Major institutions[edit] This non-exhaustive list includes those institutions and universities with major groups of people working in planetary science. Alphabetical order is used. National space agencies[edit]

Ames (NASA) Canadian Space Agency
Canadian Space Agency
(CSA). Annual budget CAD $488.7 million (2013–2014). China National Space Administration
China National Space Administration
(CNSA) (People's Republic of China). Budget $0.5-1.3 Billion (est.). Centre national d'études spatiales French National Centre of Space Research,Budget €1.920 Billion (2012). Deutsches Zentrum für Luft- und Raumfahrt e.V., (German: abbreviated DLR), the German Aerospace Center.Budget $2 Billion (2010). European Space Agency
European Space Agency
(ESA). Budget $5.51 Billion (2013). Russian Federal Space Agency
Russian Federal Space Agency
Budget $5.61 Billion (2013). GSFC (NASA), Indian Space Research Organisation
Indian Space Research Organisation
(ISRO), Israel Space Agency
Israel Space Agency
(ISA), Italian Space Agency
Italian Space Agency
Budget ~$1 Billion (2010). Japan Aerospace Exploration Agency
Japan Aerospace Exploration Agency
(JAXA). Budget $2.15 Billion (2012). JPL (NASA), NASA: Considerable number of research groups, including the JPL, GSFC, Ames. Budget $18.724 Billion (2011). National Space Organization (Republic of China in Taiwan). UK Space Agency
UK Space Agency
(UKSA).

Other institutions[edit]

The Australian National University's Planetary Science Institute Brown University
Brown University
Planetary Geosciences Group Caltech's Division of Geological and Planetary Sciences and Planetary Sciences subdivision Cornell University's Space and Planetary Science Florida Institute of Technology's Department of Physics and Space Sciences Johns Hopkins University's Applied Physics Laboratory Lunar and Planetary Institute Max Planck Institute for Solar System
Solar System
Research's Department Planets and Comets MIT Dept. of Earth, Atmospheric and Planetary Sciences Open University
Open University
Planetary and Space Sciences Research Institute Planetary Science Institute Stony Brook University's Geosciences Department and soon to open Center for Planetary Exploration UCL/Birkbeck's Centre for Planetary Sciences University of Arizona's Lunar and Planetary Lab University of Arkansas's Center for Space and Planetary Sciences University of California Los Angeles's Department of Earth, Planetary, and Space Sciences University of California Santa Cruz's Department of Earth
Earth
& Planetary Sciences University of Hawaii's Hawaii Institute of Geophysics
Geophysics
and Planetology University of Copenhagen's Center for Planetary Research University of Central Florida
University of Central Florida
Planetary Sciences Group University of British Columbia
University of British Columbia
Department of Earth, Ocean and Atmospheric Sciences University of Western Ontario's Centre for Planetary Science and Exploration University of Tennessee
University of Tennessee
Department of Earth
Earth
and Planetary Sciences University of Colorado's Department of Astrophysical and Planetary Sciences INAF– Istituto di Astrofisica e Planetologia Spaziali [1]

Basic concepts[edit]

Asteroid Celestial mechanics Comet Dwarf planet Extrasolar planet Gas giant Icy moon Kuiper belt Magnetosphere Minor planet Planet Planetary differentiation Planetary system Definition of a planet Space weather Terrestrial planet

See also[edit]

Selenography
Selenography
- study of the surface and physical features of the Moon Theoretical planetology Timeline of Solar System
Solar System
exploration

References[edit]

^ a b Taylor, Stuart Ross (29 July 2004). "Why can't planets be like stars?". Nature. 430 (6999): 509. Bibcode:2004Natur.430..509T. doi:10.1038/430509a. PMID 15282586.  ^ Hippolytus (Antipope); Origen (1921). Philosophumena (Digitized 9 May 2006). 1. Translation by Francis Legge, F.S.A. Original from Harvard University.: Society for promoting Christian knowledge. Retrieved 22 May 2009.  ^ Taylor, Stuart Ross (1994). "Silent upon a peak in Darien". Nature. 369 (6477): 196–7. Bibcode:1994Natur.369..196T. doi:10.1038/369196a0.  ^ Stern, Alan. "Ten Things I Wish We Really Knew In Planetary Science". Retrieved 2009-05-22.  ^ http://www.uwyo.edu ^ curator.jsc.nasa.gov/antmet/lmc/lmcintro.pdf

Further reading[edit]

Carr, Michael H., Saunders, R. S., Strom, R. G., Wilhelms, D. E. 1984. The Geology of the Terrestrial Planets. NASA. Morrison, David. 1994. Exploring Planetary Worlds. W. H. Freeman. ISBN 0-7167-5043-0

External links[edit]

Find more aboutPlanetary scienceat's sister projects

Definitions from Wiktionary Media from Wikimedia Commons News from Wikinews Quotations from Wikiquote Texts from Wikisource Textbooks from Wikibooks Learning resources from Wikiversity

Planetary Science Research Discoveries (articles) The Planetary Society (world's largest space-interest group: see also their active news blog) Planetary Exploration Newsletter (PSI-published professional newsletter, weekly distribution) Women in Planetary Science (professional networking and news)

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Major subfields of astronomy and astrophysics

Astrobiology Astrochemistry Astrometry Cosmochemistry Cosmology Extragalactic astronomy Galactic astronomy Orbital mechanics Physical cosmology Planetary geology Planetary science Solar astronomy Stellar astronomy

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Exoplanetology

Planet

Definition

IAU

Planetary science

Main topics

Exoplanet Methods of detecting exoplanets Planetary system

Sizes and types

Terrestrial

Carbon planet Coreless planet Desert planet Dwarf planet Ice planet Iron planet Lava planet Mega-Earth Ocean planet Sub-Earth Super-Earth

Gaseous

Chthonian planet Eccentric Jupiter Gas dwarf Helium planet Hot Jupiter Hot Neptune Ice giant Mini-Neptune Super-Neptune Super-Jupiter

Other types

Brown dwarf Circumbinary planet Double planet Mesoplanet Planemo Planet/ Brown dwarf
Brown dwarf
boundary Planetesimal Protoplanet Pulsar planet Sub-brown dwarf Ultra-cool dwarf Ultra-short period planets
Ultra-short period planets
(USP)

Formation and evolution

Accretion Merging stars Nebular hypothesis Planetary migration

Systems

Exocomet Exomoon Interstellar comet Mean-motion resonances Retrograde planet Rogue planet Titius–Bode laws Trojan planet

Host stars

A B Binary star Brown dwarfs Extragalactic planet F/Yellow-white dwarfs G/Yellow dwarfs Herbig Ae/Be K/Orange dwarfs M/Red dwarfs Planets in globular clusters Pulsar Red giant Subdwarf B Subgiant T Tauri White dwarfs Yellow giant

Detection

Astrometry Direct imaging

list

Microlensing

list

Polarimetry Pulsar timing

list

Radial velocity

list

Transit method

list

Transit-timing variation

Habitability

Astrobiology Circumstellar habitable zone Earth
Earth
analog Extraterrestrial liquid water Habitability of natural satellites Superhabitable planet

Catalogues

Catalog of Nearby Habitable Systems Exoplanet
Exoplanet
Data Explorer Extrasolar Planets Encyclopaedia NASA
NASA
Exoplanet
Exoplanet
Archive NASA
NASA
Star and Exoplanet
Exoplanet
Database

Lists

Exoplanetary systems

Host stars Multiplanetary systems Stars with proplyds

Exoplanets

List of exoplanets Discoveries Extremes Firsts Nearest Largest Most massive Terrestrial candidates Kepler Potentially habitable

Discovered exoplanets by year

before 2000 2000–2009 2010 2011 2012 2013 2014 2015 2016 2017 2018

Other

Carl Sagan Institute Exoplanet
Exoplanet
phase curves Nexus for Exoplanet
Exoplanet
System Science Planets in science fiction Sudarsky's gas giant classification

Discoveries of exoplanets Search projects

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Planetary defense

Main topics

Asteroid Bolide Earth-grazing fireball Impact event

List of meteor air bursts

Meteor procession Meteor shower Meteorite Meteoroid Near- Earth
Earth
object Potentially hazardous object

Defense

Asteroid
Asteroid
impact avoidance Asteroid
Asteroid
close approaches Earth-crossing minor planets Gravity
Gravity
tractor Ion Beam Shepherd Damage scales

Palermo scale Torino scale

Space probes

Dawn Deep Impact DART Halley Armada Hayabusa Hayabusa2

MASCOT

NEAR Shoemaker NEA Scout New Horizons OSIRIS-REx PROCYON Rosetta

Philae

Stardust

NEO tracking

ATLAS Catalina Sky Survey LINEAR LONEOS NEAT NEOSSat NEOCam NEODyS OGS Telescope Orbit@home Pan-STARRS SCAP Sentinel Space Telescope Sentry Spacewatch WISE

Organizations

B612 Foundation Japan Spaceguard
Spaceguard
Association Meteoritical Society NEOShield Spaceguard The Spaceguard
Spaceguard
Foundation Space Situational Awareness Programme Planetary Defense Coordination Office

Potential threats

1950 DA 1994 WR12 101955 Bennu 2002 MN (410777) 2009 FD 2010 RF12 99942 Apophis

Films / video

The End of the World (1916) When Worlds Collide (1951) Gorath
Gorath
(1962) The Green Slime
The Green Slime
(1968) The Paradise Syndrome
The Paradise Syndrome
(1968) A Fire in the Sky
A Fire in the Sky
(1978) Meteor (1979) NOVA: Doomsday Asteroid
Asteroid
(1995) Asteroid
Asteroid
(1997) Deep Impact (1998) Armageddon (1998) Avengers: Age of Ultron (2015) Judgment Day (1999) Post Impact
Post Impact
(2004) Deadly Skies (2006) Super Comet: After the Impact (2007) Impact (2009) NOVA: Last Extinction (2009) Meteor Storm
Meteor Storm
(2010) HORIZON: Asteroids–The Good, the Bad and the Ugly (2010) Melancholia (2011) NOVA: Meteor Strike (2013) NOVA: Asteroid: Doomsday or Payday? (2013) Impact Earth
Earth
(2015)

Authority control

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