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Crater astronomy
[[Image:Chain of impact craters on Ganymede.jpg|thumb|right|200px|The image shows a chain of craters on Ganymede. Credit: Galileo Project, Brown University, JPL, NASA.]]
A '''crater''' may be any large, roughly circular, depression or hole in or beneath the rocky surface of a rocky object.
{{experimental}}
'''Crater astronomy''' applies the techniques of astronomy to the apparent craters observed on rocky objects in an effort to understand what they are, when they occurred, and their importance to rocky objects.
{{article}}
{{lecture}}
{{astronomy}}
{{astrophysics}}
{{geography}}
{{geology}}
{{Materials scienceclear}}

=[[Astronomy]]=

When any effort to acquire a system of laws or knowledge focusing on an ''astr'', ''aster'', or ''astro'', that is, any natural body in the sky especially at night,<ref name=Gove>{{ cite book
|author=
|title=Webster's Seventh New Collegiate Dictionary
|publisher=G. & C. Merriam Company
|location=Springfield, Massachusetts
|year=1963
|editor=Philip B. Gove
|pages=1221
|bibcode=
|doi=
|pmid=
|isbn=
|accessdate=2011-08-26 }}</ref> succeeds in discovering or exploring craters even in its smallest [[measurement]], '''crater astronomy''' is the name of the effort and the result. Once an entity, source, or object has been detected as having craters, it may be necessary to determine what the mechanism is. Usually this information provides understanding of the same entity, source, or object. Craters suggests a violent event. The formation of craters on [[Earth]] may be associated with the sense of seeing as much as hearing, what can be termed [[acoustic astronomy]]. As telescope optics transmit visual light well, [[visual astronomy]] is a field associated with crater astronomy.

For crater astronomy, the proof of concept is demonstrated by unique or novel [[astronomy]] in any band that explores craters to reveal knowledge, especially regarding their formation.

=[[Radiation]]=

Radiation that may produce a crater are likely larger than subatomic particles. The range of size and composition of this radiation is large. Such radiation may be rocky, liquid, gaseous, or plasma, a moving galaxy cluster to down to the size of an atom, molecule, or dust.

The characteristics of the crater likely depend on the energy of impact broken down into at least angle, speed, media, and dissipation.

=[[Planets/Geology|Planetary geology]]=
[[Image:Moon-apollo17-schmitt boulder.jpg|thumb|right|200px|Planetary geologist and NASA astronaut Harrison "Jack" Schmitt collects lunar samples during the Apollo 17 mission. Credit: NASA.]]
"'''Planetary geology''', ... '''astrogeology''' or '''exogeology''', is a [[planetary science]] ... concerned with the [[geology]] of the celestial bodies such as theplanets and their [[moon]]s, asteroids, comets, and [[meteorites]]. ... [It includes] determining the internal structure of the terrestrial planets, ... planetary volcanism and surface processes such as impact craters, fluvial and aeolian processes."<ref name=Planetarygeology>{{ cite web
|title=Planetary geology, In: ''Wikipedia''
|publisher=Wikimedia Foundation, Inc
|location=San Francisco, California
|month=May 22,
|year=2012
|url=http://en.wikipedia.org/wiki/Planetary_geology
|accessdate=2012-05-23 }}</ref>
{{clear}}

=[[Minerals]]=
[[Image:LvMS-Lvm.jpg|thumb|left|200px|The photomicrographs show of a sand grain held in an amorphous matrix, in plane-polarized light on top, cross-polarized light on bottom. Scale box in mm. Credit: [[w:User:Qfl247|Qfl247]].]]
[[Image:820qtz.jpg|thumb|left|200px|This is a thin section with cross-polarized kight through a sand-sized quartz grain of 0.13 mm diameter. Credit: Glen A. Izett, USGS.]]
[[Image:Suvasvesi shocked quartz.jpg|thumb|right|200px|This is a thin section of a shocked quartz grain. Credit: Martin Schmieder.]]
Alpha-quartz (space group ''P''3<sub>1</sub>21, no. 152, or ''P''3<sub>2</sub>21, no. 154) under a high pressure of 2-3 gigapascals and a moderately high temperature of 700°C changes space group to monoclinic ''C''2/c, no. 15, and becomes the mineral coesite. It is "found in extreme conditions such as the impact craters of meteorites".<ref name=Coesite>{{ cite web
|title=coesite, In: ''Wiktionary''
|publisher=Wikimedia Foundation, Inc
|location=San Francisco, California
|month=August 3,
|year=2012
|url=http://en.wiktionary.org/wiki/coesite
|accessdate=2012-10-23 }}</ref>.

"Shocked quartz is associated with two high pressure polymorphs of silicon dioxide: coesite and stishovite. These polymorphs have a crystal structure different from standard quartz. Again, this structure can only be formed by intense pressure, but moderate temperatures. High temperatures would anneal the quartz back to its standard form."<ref name=ShockedQuartz>{{ cite web
|title=Shocked quartz, In: ''Wikipedia''
|publisher=Wikimedia Foundation, Inc
(contracted; show full)
|author=Glen A. Izett
|title=Shocked Quartz from the USGS -- NASA Langley Core
|publisher=U. S. Geological Survey
|location=
|month=September 26,
|year=2000
|url=http://geology.er.usgs.gov/eespteam/crater/shockquartz.html

|pdf=⏎
|accessdate=2012-10-23 }}</ref> "Very high pressures produced by strong shock waves cause dislocations in the crystal structure of quartz grains along preferred orientations. These dislocations appear as sets of parallel lamellae in the quartz when viewed with a petrographic microscope. Bolide impacts are the only natural process known to produce shock lamellae in quartz grains."<ref name=Izett/>

(contracted; show full)|issue=
|pages=458-74
|url=http://ukpmc.ac.uk/abstract/MED/11541098
|arxiv=
|bibcode=
|doi=
|pmid=11541098

|pdf=⏎
|accessdate=2012-10-23 }}</ref>

"As with the North American microtektite-bearing cores, all the Australasian microtektite-bearing cores containing coesite and shocked quartz also contained volcanic ash, which complicated the search."<ref name=Glass>{{ cite journal
|author=B. P. Glass and Jiquan Wu
|title=Coesite and shocked quartz discovered in the, Australasian and North American, microtektite layers
|journal=Geology
|month=May
|year=1993
|volume=21
|issue=5
|pages=435-8
|url=http://geology.geoscienceworld.org/content/21/5/435.short
|arxiv=
|bibcode=
|doi=10.1130/​0091-7613(1993)​021<0435:CASQDI>​2.3.CO;2
|pmid=
|pdf=⏎
|accessdate=2012-10-23 }}</ref>
{{clear}}

=Theoretical crater astronomy=
[[Image:Mount Mazama eruption timeline.PNG|thumb|right|200px|Example of the formation of a caldera, the pictures show Mount Mazama's eruption timeline. Credit: .]]
A "cataclysm [may] have affected the entire inner Solar System ... [when] numerous main-belt asteroids ... were driven onto high-velocity and highly eccentric orbits by the effects of the late migration of the giant planets."<ref name=Marchi>{{ cite journal
|author=S. Marchi, W. F. Bottke, B. A. Cohen, K. Wünnemann, D. A. Kring, H. Y. McSween, M. C. De Sanctis, D. P. O’Brien, P. Schenk, C. A. Raymond & C. T. Russell
|title=High-velocity collisions from the lunar cataclysm recorded in asteroidal meteorites
|journal=Nature Geoscience
|month=March
|year=2013
|volume=6
|issue=4
|pages=303-7
|url=http://www.nature.com/ngeo/journal/v6/n4/full/ngeo1769.html
|arxiv=
|bibcode=
|doi=10.1038/ngeo1769
|pmid=
|pdf=⏎
|accessdate=2013-03-29 }}</ref>

The sequence of figures depict a likely model for caldera collapse.

"A collapse is triggered by the emptying of the magma chamber beneath the volcano, usually as the result of a large volcanic eruption. If enough magma is ejected, the emptied chamber is unable to support the weight of the ''volcanic edifice'' above it. A roughly circular fracture, the ''ring fault'', develops around the edge of the chamber. Ring fractures s(contracted; show full)

"Crater chains seen on the [[Moon]] often radiate from larger craters, and in such cases are thought to be either caused by secondary impacts of the larger crater's ejecta or by volcanic venting activity along a rift.<ref name=Apollo>{{ cite web
|url=http://www.hq.nasa.gov/office/pao/History/SP-362/ch5.3.htm
|title=Apollo over  the Moon - Chapter 5: Craters
|accessdate=2008-02-03 }}</ref>"<ref name=CraterChain/>
{{clear}}

=
Entities[[Radiation astronomy/Entities|Entities]]=
[[Image:Vulkanbombeneinschlag.png|thumb|right|200px|A volcanic bomb has deformed the rock strata. Credit: [[:de:User:Drucker03|Drucker03]].]]
'''Def.'''
# the "study of rock layers and the layering process [of] stratification"<ref name=StratigraphyWikt>{{ cite web
|title=stratigraphy, In: ''Wiktionary''
|publisher=Wikimedia Foundation, Inc
|location=San Francisco, California
|month=October 8,
(contracted; show full)|issue=03
|pages=388
|url=http://adsabs.harvard.edu/abs/1974LPI.....5..388J
|arxiv=
|bibcode=1974LPI.....5..388J
|doi=
|pmid=

|pdf=⏎
|accessdate=2013-10-18 }}</ref>

: <math> C_D = S (D/D_0)^{-n},</math>

where <math>C_D</math> is change in particle diameter, <math>S</math> is the constant of surface area rate of change, <math>D</math> is the measured particle diameter in the soil, <math>D_0</math> is the initial particle diameter for all samples, and <math>n</math> is the exponent.
{{clear}}

=Sources[[Radiation astronomy/Sources|Sources]]=
[[Image:Mount Tambora Volcano, Sumbawa Island, Indonesia.jpg|thumb|right|200px|This detailed astronaut photograph depicts the summit caldera of the Mount Tambora. Credit: NASA ISS Expedition 20 crew.]]
[[Image:Santa Ana Volcano.USAF.C-130.3.jpg|right|thumb|200px|The crater in Santa Ana Volcano is photographed from a United States Air Force C-130 Hercules flying above El Salvador. Credit: .]]
[[Image:Karthala volcano-Comoros.jpg|thumb|left|200px|The view is into Karthala volcano crater in November 2006 at the solidified lava lake Credit: alKomor.com.]]
[[Image:SP Crater.jpg|thumb|right|200px|S P Crater is a cinder cone volcano in the San Francisco volcanic field. Credit: .]]
The first image at right is a "detailed astronaut photograph [that] depicts the summit caldera of the volcano. The huge caldera—6 kilometers (3.7 miles) in diameter and 1,100 meters (3,609 feet) deep—formed when Tambora’s estimated 4,000-meter- (13,123-foot) high peak was removed, and the magma chamber below emptied during the April 10 eruption. Today the crater floor is occupied by an ephemeral freshwater lake, recent sedimentary deposits, and minor lava flows and domes from the nineteenth and twentieth centuries. Layered tephra deposits are visible along the northwestern crater rim. Active fumaroles, or steam vents, still exist in the caldera."<ref name=Wiscombe>{{ cite web
|author=Warren Wiscombe
|title=Mount Tambora Volcano, Sumbawa Island, Indonesia
|publisher=NASA Earth Observatory
|location=
|month=July 19,
|year=2009
|url=http://earthobservatory.nasa.gov/IOTD/view.php?id=39412
|pdf=⏎
|accessdate=2013-03-30 }}</ref>

"On April 10, 1815, the Tambora Volcano produced the largest eruption in recorded history. An estimated 150 cubic kilometers (36 cubic miles) of tephra—exploded rock and ash—resulted, with ash from the eruption recognized at least 1,300 kilometers (808 miles) away to the northwest. While the April 10 eruption was catastrophic, historical records and geological analysis of eruption deposits indicate that the volcano had been active between 1812 and 1815. Enough ash(contracted; show full)|issue=03
|pages=537
|url=http://adsabs.harvard.edu/full/1992LPI....23..537H
|arxiv=
|bibcode=1992LPI....23..537H
|doi=
|pmid=

|pdf=⏎
|accessdate=2013-10-18 }}</ref>

"In agreement with many authors (Pal et al., 1982; Klein and Middleton, 1984; Blum et al., 1992), we therefore exclude meteoritic and lunar material as sources for the <sup>10</sup>Be in the Australasian tektites, and, by a short extension, for virtually all the other atoms in the tektites."<ref name=Ma>{{ cite journal
|author=P. Ma, K. Aggrey, C. Tonzola, C. Schnabel, P. de Nicola, G.F. Herzog, J.T. Wasson, B.P. Glass, L. Brown, F. Tera, R. Middleton, J. Klein
|title=Beryllium-10 in Australasian tektites: constraints on the location of the source crater
|journal=Geochimica et Cosmochimica Acta
|month=October
|year=2004
|volume=68
|issue=19
|pages=3883-96
|url=http://www.sciencedirect.com/science/article/pii/S0016703704002741
|arxiv=
|bibcode=
|doi=
|pmid=
|pdf=⏎
|accessdate=2013-10-18 }}</ref>
{{clear}}

=Objects[[Radiation astronomy/Objects|Objects]]=
[[Image:Mare Imbrium-Apollo17.jpg|thumb|200px|right|Mare Imbrium (foreground) is peppered with secondary craters from the impact that formed Copernicus crater (upper center). Credit: NASA.]]
'''Def.''' "[a] hemispherical pit ... [a] basinlike opening or mouth ... about which a cone is often built up ... any large roughly circular depression or hole"<ref name=CraterWikt>{{ cite web
|title=crater, In: ''Wiktionary''
(contracted; show full)|issue=
|pages=617-28
|url=http://adsabs.harvard.edu/abs/1977iecp.symp..617S
|arxiv=
|bibcode=
|doi=
|pmid=

|pdf=⏎
|accessdate=2013-10-18 }}</ref>

"Phoebe is a densely cratered object. Cumulative numbers of craters, between 100 m and 100 km diameter, per unit area, define a steep-sloped curve (Fig. 5). Crater densities approach those seen on other heavily cratered objects (15, 16)."<ref name=Porco>{{ cite journal
|author=C. C. Porco1, E. Baker, J. Barbara, K. Beurle, A. Brahic, J. A. Burns, S. Charnoz, N. Cooper, D. D. Dawson, A. D. Del Genio, T. Denk, L. Dones, U. Dyudina, M. W. Evans, B. Giese, K. Grazier, P. Helfenstein, A. P. Ingersoll, R. A. Jacobson, T. V. Johnson, A. McEwen, C. D. Murray, G. Neukum, W. M. Owen, J. Perry, T. Roatsch, J. Spitale, S. Squyres, P. C. Thomas, M. Tiscareno, E. Turtle, A. R. Vasavada, J. Veverka, R. Wagner, R. West
|title=Cassini imaging science: Initial results on Phoebe and Iapetus
|journal=Science
|month=February
|year=2005
|volume=307
|issue=5713
|pages=1237-42
|url=http://www.sciencemag.org/content/307/5713/1237.short
|arxiv=
|bibcode=
|doi=
|pmid=
|pdf=⏎
|accessdate=2013-10-18 }}</ref>
{{clear}}

=[[Charges/Strong interactions|Strong forces]]=
[[Image:La Cumbre - ISS.JPG|thumb|right|200px|This satellite photograph is of the summit caldera on Fernandina Island in the Galapagos archipelago. Credit: .]]
[[Image:Pinatubo92pinatubo caldera crater lake.jpg|thumb|left|200px|Mt.Pinatubo is in the Philippines. Credit: .]]
[[Image:Crater lake oregon.jpg|thumb|left|200px|Crater Lake, Oregon, formed around 5,680 BC. Credit: .]]
[[Image:Aniakchak-caldera alaska.jpg|thumb|left|200px|Aniakchak-caldera, Alaska shows a characteristic caldera. Credit: .]]
(contracted; show full)Toba catastrophe theory). More recently several geneticists, including Lynn Jorde and Henry Harpending have proposed that the human race was reduced to approximately five to ten thousand people.<ref name=Supervolcano>[http://www.bbc.co.uk/science/horizon/1999/supervolcanoes_script.shtml Supervolcanoes], BBC2, 3 February 2000</ref> Whichever figure is right, the fact remains that the human race seemingly came close to extinction about 75,000 years ago."<ref name=Caldera/>
{{clear}}

=
[[Charges/Electromagnetic interactions|Electromagnetics]]=
[[Image:Davy Crater region hi res.jpg|thumb|right|200px|The Davy crater chain (arrow) is one of the most spectacular chains of craters on the Moon. Credit: NASA.]]
(contracted; show full)|pages=69-77
|url=http://books.google.com/books?hl=en&lr=&id=DBDe-vhGTR0C&oi=fnd&pg=PP1&ots=CIEnZrYfQI&sig=4waK0rG-TNNQwTqCAT9FpPp3WLI#v=onepage&f=false
|arxiv=
|bibcode=
|doi=
|pmid=
|isbn=

|pdf=⏎
|accessdate=2012-06-12 }}</ref>

“[M]ost features now being photographed on planets, satellites, and asteroids are scars of plasma discharges: interplanetary lightning.”<ref name=Acheson/>

(contracted; show full)|issue=Suppl 2-M4
|pages=185-90
|url=http://www.benthamscience.com/open/toaaj/articles/V004/SI0162TOAAJ/185TOAAJ.pdf
|arxiv=
|bibcode=
|doi=
|pmid=

|pdf=⏎
|accessdate=2013-10-18 }}</ref>

“A superbolt, more powerful than an ordinary lightning bolt, struck a cornfield near Leland, Illinois, leaving a crater one foot deep, and breaking windows in homes almost a mile away.<ref name=Burt>Christopher C. Burt, ''Extreme Weather: A Guide & Record Book'' (W. W. Norton & Company, 2007), p149</ref>”<ref name=April1959>{{ cite web
|title=April 1959, In: ''Wikipedia''
|publisher=Wikimedia Foundation, Inc
|location=San Francisco, California
|month=June 9,
|year=2012
|url=http://en.wikipedia.org/wiki/April_1959
|accessdate=2012-06-12 }}</ref>
{{clear}}

=[[Radiation astronomy/Continua|Continuum]]=

"Croft [3] called moat craters anomalous pit craters and also suggested a continuum between moat craters, craters, and palimpsests, even though morphometrically they appeared to be distinct."<ref name=Lucchitta>{{ cite journal
|author=B.K. Lucchitta and H.M. Ferguson
|title=Ganymede: "Moat" Craters Compared with Palimpsests and Basins
|journal=Abstracts of the Lunar and Planetary Science Conference
|month=March
|year=1988
|volume=19
|issue=03
|pages=701
|url=http://adsabs.harvard.edu/full/1988LPI....19..701L
|arxiv=
|bibcode=1988LPI....19..701L
|doi=
|pmid=
|pdf=⏎
|accessdate=2013-10-18 }}</ref>

=Emissions[[Radiation astronomy/Emissions|Emissions]]=
[[Image:Toba zoom.jpg|thumb|left|200px|Landsat captures an image of Lake Toba, on the island of Sumatra, Indonesia. Credit: .]]
[[Image:Whetstone Sulky 001.jpg|thumb|right|200px|Rubble mound, or dome, formed by the Operation Whetstone Sulky explosion. Credit: .]]
[[Image:Callisto Har PIA01054.jpg|thumb|right|200px|This is a Galileo image of Hár. Credit: NASA.]]
(contracted; show full)
|author=Kerry Sieh
|title=Long Valley Caldera Field Guide - Panum Crater
|publisher=USGS
|location=
|month=January 31,
|year=2012
|url=http://volcanoes.usgs.gov/volcanoes/long_valley/long_valley_sub_page_17.html

|pdf=⏎
|accessdate=2013-03-30 }}</ref>

"At Panum, a pyroclastic eruption (new magma explosively fragmented into the air) followed the phreatic (steam) eruption. During a pyroclastic eruption, the gas within the magma continues to expand and escape as the magma is thrown into the air and cools. The resulting deposits included ash (particles <2mm in size) and pumice. The pumice is frothy preserving the frozen gas bubbles."<ref name=Sieh/>

(contracted; show full)

"Flow banding containing both obsidian and pumice is common at Panum Crater. Another common texture, called breadcrust, can also be seen in the dome. Breadcrust textures form when the inside of a cooling rock is still hot with gas escaping from it while the outside surface has already cooled. As the gas expands from the inside, the outside surface cracks to allow the gas to escape."<ref name=Sieh/>
{{clear}}

=
Absorptions[[Radiation astronomy/Absorptions|Absorptions]]=
[[Image:Sedan Plowshare Crater.jpg|thumb|right|200px|This image shows the crater created by the Sedan shallow underground nuclear test explosion. Credit: National Nuclear Security Administration, Federal Government of the United States.]]
[[Image:Stylised crater.png|thumb|left|200px|This diagram depicts a stylized cross-section of a crater formed by a below-ground explosion. Credit: [[w:User:JBel|JBel]].]]
(contracted; show full)|issue=1
|pages=53-62
|url=http://www.tandfonline.com/doi/abs/10.1080/07929978.1995.10676590
|arxiv=
|bibcode=
|doi=10.1080/07929978.1995.10676590
|pmid=

|pdf=⏎
|accessdate=2013-10-16 }}</ref>

"Erosional craters (Makhtesh) were formed by truncation and erosion of several of these anticlinal crests."<ref name=Fruchter>{{ cite journal
|author=N. Fruchter, A. Matmon, Y. Avni, D. Fink
|title=Revealing sediment sources, mixing, and transport during erosional crater evolution in the hyperarid Negev Desert, Israel
|journal=Geomorphology
|month=November 15,
|year=2011
|volume=134
|issue=3-4
|pages=363-77
|url=http://www.sciencedirect.com/science/article/pii/S0169555X11003564
|arxiv=
|bibcode=
|doi=
|pmid=
|pdf=⏎
|accessdate=2013-10-16 }}</ref>

At lower left, the image is an oblique aerial photo of Makhtesh Hazera. The Makhtesh drainage divide is outlined by a bold black line, with both of its constituent features (the anticlinal valley and the Upper Basin) located.<ref name=Fruchter/>
{{clear}}

=Bands[[Radiation astronomy/Bands|Bands]]=
[[Image:Tycho crater on the Moon.jpg|thumb|right|200px|The prominent impact crater is Tycho on the Moon. Credit: NASA.]]
[[Image:Impact movie.ogg|thumb|left|200px|A laboratory simulation of an impact event and crater formation is shown. Credit: .]]
[[Image:Craterstructure.gif|thumb|right|200px|Impact crater structure is diagrammed. Credit: .]]
(contracted; show full)
|author=Heidi Koontz and Robert McKay
|title=Iowa Meteorite Crater Confirmed
|publisher=U.S. Geological Survey
|location=12201 Sunrise Valley Dr, MS 119 Reston, Virginia 20192 USA
|month=March 5,
|year=2013
|url=http://www.usgs.gov/newsroom/article.asp?ID=3521#.UVfS467Qorc

|pdf=⏎
|accessdate=2013-03-30 }}</ref>

"Capturing images of an ancient meteorite impact was a huge bonus," said Dr. Paul Bedrosian, a USGS geophysicist in Denver who is leading the effort to model the recently acquired geophysical data.<ref name=Koontz/> "These findings highlight the range of applications that these geophysical methods can address."<ref name=Koontz/>

(contracted; show full); ergs. The oblique impacts produce craters 2 to 10 m across with morphologies and ejecta that are bilaterally symmetrical with respect to the plane of the missile trajectory. Rims are high and the amount of ejecta large in down-trajectory and lateral directions, whereas rims are low to nonexistent and ejecta thin to absent up-trajectory. Symmetry development and modifications of the symmetry are a function of target material, local topography, and angle of impact."<ref name=Moore/>
{{clear}}

=
[[Mercury]]=
[[Image:Mercury Globe-MESSENGER mosaic centered at 0degN-0degE.jpg|thumb|right|200px|This is a composite image of Mercury taken by the MESSENGER probe. Credit: .]]
[[Image:Mariner 10.jpg|thumb|left|200px|Mariner&nbsp;10 is the first probe to visit the innermost planet (1974–75). Credit: .]]
{{multiple image
| align = left
| direction = horizontal
| width = 230
| image1 = Caloris basin labeled.png
(contracted; show full)

"Mariner&nbsp;10 provided the first close-up images of Mercury's surface, which immediately showed its heavily cratered nature"<ref name=MercuryPlanet/>

At right is an example of catena on Mercury.
{{clear}}

=
[[Venus]]=
[[Image:Mgn p39146.png|thumb|right|200px|Impact craters on the surface of Venus (image reconstructed from radar data) are shown. Credit: NASA.]]
"The absence of evidence of lava flow accompanying any of the visible caldera remains an enigma. The planet has few impact craters".<ref name=Venus>{{ cite web
|title=Venus, In: ''Wikipedia''
|publisher=Wikimedia Foundation, Inc
|location=San Francisco, California
|month=March 18September 27,
|year=20132
|url=http://en.wikipedia.org/wiki/Venus
|accessdate=2013-042-10-034 }}</ref>

"After the Venera missions were completed, the prime meridian was redefined to pass through the central peak in the crater Ariadne.<ref>{{ cite web
|url=http://astrogeology.usgs.gov/Projects/WGCCRE/constants/iau2000_table1.html
|title=USGS Astrogeology: Rotation and pole position for the Sun and planets (IAU WGCCRE)
|accessdate=22 October 2009 }}</ref><ref>{{ cite web
|url=http://www2.jpl.nasa.gov/magellan/guide8.html
|title=The Magellan Venus Explorer's Guide
(contracted; show full)|title = The Planetary System
|author = David Morrison
|year = 2003
|publisher = Benjamin Cummings
|isbn = 0-8053-8734-X }}</ref>"<ref name=Venus/>
{{clear}}

=
[[Earth]]=
[[Image:Barringer Crater aerial photo by USGS.jpg|thumb|left|200px|This is an aerial view of the Barringer Meteor Crater about 69 km east of Flagstaff, Arizona USA. Credit: D. Roddy, U.S. Geological Survey (USGS).]]
[[Image:Meteor Crater - Arizona.jpg|thumb|right|200px|This is a Landsat image of the Barringer Meteor Crater from space. Credit: National Map Seamless Server, NASA Earth Observatory.]]
(contracted; show full), 110 km), and span 43.5° of palaeolongitude. These structures may thus represent the remains of a crater chain at least 4,462 km long. The Obolon' and Red Wing craters, on the other hand, lie on great circles of identical declination with Rochechouart and Saint Martin, respectively. [...] the five impact structures were [likely] formed at the same time (within hours) during a multiple impact event caused by a fragmented comet or asteroid colliding with Earth."<ref name=Spray/>
{{clear}}

=
[[Moon]]=
[[Image:Carte Lune mers crateres.jpg|thumb|right|200px|The image is a map in French of the Moon showing the maria and the major craters. Credit: additions made to Lune22h27septembre2004.jpg created by Yves under GFDL by Eric Gaba ([[commons:User:Sting|Sting]] - fr:Sting).]]
(contracted; show full)
|author=Jon Nelson
|title=Earth's Moon
|publisher=NASA/JPL/USGS
|location=
|month=June 8,
|year=1998
|url=http://www.jpl.nasa.gov/spaceimages/details.php?id=PIA00405

|pdf=⏎
|accessdate=2012-09-26 }}</ref>

The dark irregular mare lava plains are prominent in the fully illuminated disk. A single bright star of ejecta, with rays stretching a third of the way across the disk, emblazons the lower centre: this is the crater Tycho on the Near side of the Moon. But, on the far side, the full disk is nearly featureless, a uniform grey surface with almost no dark mare. There are many bright overlapping dots of impact craters. And, an almost complete lack of dark maria.<ref nam(contracted; show full)
|author=Jim Wilson
|title=Water Around a Fresh Crater
|publisher=NASA
|location=
|month=September 24,
|year=2009
|url=http://www.nasa.gov/topics/moonmars/features/clark3.html

|pdf=⏎
|accessdate=2012-09-26 }}</ref>

"Very precise microwave measurements between two spacecraft, named Ebb and Flow, were used to map gravity with high precision and high spatial resolution. The field shown [at right] resolves blocks on the surface of about 12 miles (20 kilometres) and measurements are three to five orders of magnitude improved over previous data. Red corresponds to mass excesses and blue corresponds to mass deficiencies. The map shows more small-scale detail on the far side of the moon compared to the nearside because the far side has many more small craters."<ref name=Greicius>{{ cite web
|author=Tony Greicius
|title=GRAIL's Gravity Map of the Moon
|publisher=NASA/JPL-Caltech/MIT/GSFC
|location=
|month=December 6,
|year=2012
|url=http://www.nasa.gov/mission_pages/grail/multimedia/zuber4.html
|pdf=⏎
|accessdate=2012-12-15 }}</ref>

"Crystallized spheres of orange glass from Shorty Crater at the Apollo 17 site are ... the characteristic ingredient of the dark mantling deposit of the Taurus-Littrow region."<ref name=Adams>{{ cite journal
|author=John B. Adams, Carle Pieters, and Thomas B. McCord
|title=Orange glass: Evidence for regional deposits of pyroclastic origin on the moon, In: ''Proceedings of the Fifth Lunar Science Conference''
|publisher=Pergamon Press, Inc.
|location=New York
|month=March 18-22
|year=1974
|editor=
|volume=1
|issue=
|pages=171-86
|url=http://adsabs.harvard.edu//abs/1974LPSC....5..171A
|arxiv=
|bibcode=1974LPSC....5..171A
|doi=
|pmid=
|isbn=
|pdf=⏎
|accessdate=2012-11-02 }}</ref>

"A 1953 telescopic photograph of a flash on the Moon is the only unequivocal record of the rare crash of an asteroid-sized body onto the lunar surface. ... A search of images from the Clementine mission reveals an ∼1.5-km high-albedo, blue, fresh-appearing crater with an associated ejecta blanket at the location of the flash."<ref name=Buratti>{{ cite journal
|author=Bonnie J Buratti, Lane L Johnson
|title=Identification of the lunar flash of 1953 with a fresh crater on the moon’s surface
|journal=Icarus
|month=January
|year=2003
|volume=161
|issue=1
|pages=192-7
|url=http://www.sciencedirect.com/science/article/pii/S0019103502000271
|arxiv=
|bibcode=
|doi=10.1016/S0019-1035(02)00027-1
|pmid=
|pdf=⏎
|accessdate=2012-11-27 }}</ref>

Catena Davy is a "linear string of 23 tiny craters [that] runs from the midpoint of Davy Y towards the walled basin Ptolemaeus, following a slightly curving course to the east-northeast. It is located at selenographic coordinates 11.0° S, 7.0° W, and has a diameter of 50&nbsp;km. ...  it is not radial to a suitable source crater. ... High resolution images have demonstrated that the craters formed at about the same time since the ejecta from each crater does not overlay neighboring craters."<ref name=DavyCrater>{{ cite web
|title=Davy (crater), In: ''Wikipedia''
|publisher=Wikimedia Foundation, Inc
|location=San Francisco, California
|month=February 26,
|year=2013
|url=http://en.wikipedia.org/wiki/Davy_(crater)
|accessdate=2013-03-31 }}</ref>
{{clear}}

=[[Mars]]=
[[Image:PIA15038 - Spirit lander and Bonneville Crater on Mars.jpg|thumb|right|200px|Near the lower left corner of this view of Bonneville Crater is the three-petal lander platform that NASA's Mars Exploration Rover Spirit drove off in January 2004. Credit: NASA/JPL-Caltech/Univ. of Arizona.]]
[[Image:Olympus Mons alt.jpg|thumb|right|200px|This is a top down view of Olympus Mons, the Solar system's largest known volcano. Credit: ]]
[[Image:Mars rampart crater.jpg|thumb|left|200px|This is an image of the Rampart Crater. Credit: NASA.]]
"Near the lower left corner of this view [at right] is the three-petal lander platform that NASA's Mars Exploration Rover Spirit drove off in January 2004. The lander is still bright, but with a reddish color, probably due to accumulation of Martian dust."<ref name=HiRise>{{ cite web
|author=HiRise
|title=PIA15038: Spirit Lander and Bonneville Crater in Color 
|publisher=NASA/JPL
|location=Pasadena, California USA
|month=February 8,
|year=2012
|url=http://photojournal.jpl.nasa.gov/catalog/PIA15038
|pdf=⏎
|accessdate=2013-03-31 }}</ref>

"The High Resolution Imaging Science Experiment (HiRISE) camera on NASA's Mars Reconnaissance Orbiter recorded this view on Jan. 29, 2012, providing the first image from orbit to show Spirit's lander platform in color. The view covers an area about 2,000 feet (about 600 meters) wide, dominated by Bonneveille Crater. North is up. A bright spot on the northern edge of Bonneville Crater is a remnant of Spirit's heat shield."<ref name=HiRise/>(contracted; show full)|location=San Francisco, California
|month=March 15,
|year=2013
|url=http://en.wikipedia.org/wiki/Rampart_crater
|accessdate=2013-03-31 }}</ref>
{{clear}}

=
[[Vesta]]=

"The [NASA's Dawn spacecraft] Framing Camera (FC) discovered enigmatic orange material on [[Vesta]]. FC images revealed diffuse orange ejecta around two impact craters, 34-km diameter Oppis, and 30-km diameter Octavia, as well as numerous sharp-edge orange units in the equatorial region."<ref name=Corre>{{ cite journal
|author=L Le Corre, V Reddy, KJ Becker
|title=Nature of Orange Ejecta Around Oppia and Octavia Craters on Vesta from Dawn Framing Camera
|journal=American Astronomical Society, DPS meeting
|month=October
|year=2012
|volume=
|issue=44
|pages=
|url=
|arxiv=
|bibcode=2012DPS....4420705L
|doi=
|pmid=
|pdf=⏎
|accessdate=2012-11-02 }}</ref>

=[[Callisto]]=
[[Image:Valhalla crater on Callisto.jpg|thumb|left|Multi-ringed impact basin Valhalla on Jupiter's moon Callisto is imaged. Credit: NASA/JPL.]]  
[[Image:Cratered plains PIA00745.jpg|thumb|left|200px|The ''Galileo'' image of cratered plains illustrates the pervasive local smoothing of Callisto's surface. Credit: .]]
(contracted; show full)=Lunar and Planetary Science XXXI|page=1818|url=http://www.lpi.usra.edu/meetings/lpsc2001/pdf/1818.pdf|format=PDF}}</ref> The catenae&mdash;for example Gomul Catena&mdash;are long chains of impact craters lined up in straight lines across the surface. They were probably created by objects that were tidally disrupted as they passed close to Jupiter prior to the impact on Callisto, or by very oblique impacts.<ref name="Greeley 2000"/>"<ref name=Callisto/>
{{clear}}

=
[[Europa]]=
[[Image:Europa Pwyll.jpg|thumb|right|200px|This enhanced color image is of the region surrounding the young impact crater Pwyll on Jupiter's moon Europa. Credit: NASA/Jet Propulsion Lab.]]
The image at page top right shows "[t]he prominent crater in the lower right ... Pwyll."<ref name=EuropaMoon>{{ cite web
|title=Europa (moon), In: ''Wikipedia''
|publisher=Wikimedia Foundation, Inc
|location=San Francisco, California
|month=June 22,
|year=2013
|url=http://en.wikipedia.org/wiki/Europa_(moon)
|accessdate=2013-06-24 }}</ref>

"This enhanced color image of the region surrounding the young impact crater Pwyll on Jupiter's moon Europa was produced by combining low resolution color data with a higher resolution mosaic of images obtained on December 19, 1996 by the Solid State Imaging (CCD) system aboard NASA's Galileo spacecraft. This region is on the trailing hemisphere of the satellite, centered at 11 degrees South and 276 degrees West, and is about 1240 kilometers across. North is toward the top of the image, and the sun illuminates the surface from the east."<ref name=Lavoie03061998>{{ cite web
|author=Sue Lavoie
|title=PIA01211: Pwyll Crater on Europa
|publisher=NASA's Office of Space Science
|location=Washington, DC USA
|month=March 6,
|year=1998
|url=http://photojournal.jpl.nasa.gov/catalog/PIA01211
|pdf=⏎
|accessdate=2013-06-24 }}</ref>

"The 26 kilometer diameter impact crater Pwyll, just below the center of the image, is thought to be one of the youngest features on the surface of Europa. The diameter of the central dark spot, ejecta blasted from beneath Europa's surface, is approximately 40 kilometers, and bright white rays extend for over a thousand kilometers in all directions from the impact site. These rays cross over many different terrain types, indicating that they are younger than anything they cross. Their bright white color may indicate that they are composed of fresh, fine water ice particles, as opposed to the blue and brown tints of older materials elsewhere in the image."<ref name=Lavoie03061998/>

"Also visible in this image are a number of the dark lineaments which are called "triple bands" because they have a bright central stripe surrounded by darker material. Scientists can use the order in which these bands cross each other to determine their relative ages, as they attempt to reconstruct the geologic history of Europa."<ref name=Lavoie03061998/>
{{clear}}

=[[Ganymede]]=
[[Image:Chain of impact craters on Ganymede.jpg|thumb|right|200px|The image shows a chain of craters on Ganymede. Credit: Galileo Project, Brown University, JPL, NASA.]]
[[Image:Craters on Ganymede.jpg|thumb|right|200px|The craters Gula and Achelous (bottom) are shown in the grooved terrain of Ganymede, with ejecta "pedestals" and ramparts. Credit: NASA/JPL/Brown University.]]
[[Image:Ganymede terrain.jpg|thumb|250px|right|A sharp boundary divides the ancient dark terrain of Nicholson Regio from the younger, finely striated bright terrain of Harpagia Sulcus. Credit: NASA/JPL/DLR.]]
The image at right shows a chain of 13 craters (Enki Catena) on Ganymede measuring 161.3 km in length. "The Enki craters formed across the sharp boundary between areas of bright terrain and dark terrain, delimited by a thin trough running diagonally across the center of this image. The ejecta deposit surrounding the craters appears very bright on the bright terrain. Even though all the craters formed nearly simultaneously, it is difficult to discern any ejecta deposit on the dark terrain."<ref name=EnkiCatena>{{ cite web
|title=Enki Catena, In: ''Wikipedia''
|publisher=Wikimedia Foundation, Inc
|location=San Francisco, California
|month=December 8,
|year=2012
|url=http://en.wikipedia.org/wiki/Enki_Catena
|accessdate=2013-02-16 }}</ref/>

"Cratering is seen on both types of terrain [third image at right], but is especially extensive on the dark terrain: it appears to be saturated with impact craters and has evolved largely through impact events.<ref name=Showman1999>{{ cite journal
|author=Adam P. Showman, Renu Malhotra
|title=The Galilean Satellites
|year=1999
|journal=Science
|volume=286
(contracted; show full)
|author=Sue Lavoie
|title=PIA01609: Fresh Impact Craters on Ganymede
|publisher=NASA's Office of Space Science
|location=Washington, DC USA
|month=July 15,
|year=1998
|url=http://photojournal.jpl.nasa.gov/catalog/PIA01609

|pdf=⏎
|accessdate=2013-06-22 }}</ref>

"North is to the top of the picture and the sun illuminates the surface from the right. The image, centered at 62 degrees latitude and 12 degrees longitude, covers an area approximately 142 by 132 kilometers. The resolution is 175 meters per picture element. The images were taken on April 5, 1997 at 6 hours, 33 minutes, 37 seconds Universal Time at a range of 17,531 kilometers by the Solid State Imaging (SSI) system on NASA's Galileo spacecraft."<ref name=Lavoie98/>

In the third image at right "[t]he ancient, dark terrain of Nicholson Regio (left) shows many large impact craters, and zones of fractures oriented generally parallel to the boundary between the dark and bright regions of Jupiter's moon Ganymede. In contrast, the bright terrain of Harpagia Sulcus (right) is less cratered and relatively smooth."<ref name=Lavoie2000>{{ cite web
|author=Sue Lavoie
|title=PIA02577: Bright-Dark terrain boundary, Ganymede
|publisher=NASA's Office of Space Science
|location=Washington, DC USA
|month=December 16,
|year=2000
|url=http://photojournal.jpl.nasa.gov/catalog/PIA02577
|pdf=⏎
|accessdate=2013-06-22 }}</ref>

"The nature of the boundary between ancient, dark terrain and younger, bright terrain, the two principal terrain types on Ganymede, was explored by NASA's Galileo spacecraft on May 20, 2000. Subtle parallel ridges and grooves show that Harpagia Sulcus's land has been smoothed out over the years by tectonic processes."<ref name=Lavoie2000/>

"North is to the top of the picture. The Sun illuminates the surface from the left. The image, centered at ?14 degrees latitude and 319 degrees longitude, covers an area approximately 213 by 97 kilometers (132 by 60 miles.) The resolution is 121 meters (about 250 feet) per picture element. The images were taken on May 20, 2000, at a range of 11,800 kilometers (about 7,300 miles)."<ref name=Lavoie2000/>
{{clear}}

=Io[[Io]]=
[[Image:Io highest resolution true color.jpg|thumb|right|200px|This is a true-color image of Io taken by the ''Galileo'' probe. Credit: NASA.]]
[[Image:Io VGR South polar color mosaic.jpg|thumb|left|200px|This mosaic of ''Voyager 1'' images covers Io's south polar region. The view includes two of Io's ten highest peaks, the Euboea Montes at upper extreme left and Haemus Mons at bottom. Credit: .]]
(contracted; show full)structures; mountains dominate areas with fewer volcanoes and vice versa.<ref name="McKinnon2001">{{cite journal | last=McKinnon |first=W. B. |coauthors=''et al.'' |title=Chaos on Io: A model for formation of mountain blocks by crustal heating, melting, and tilting |journal=Geology |volume=29 |issue= 2 |pages=103–106 |year=2001 |doi=10.1130/0091-7613(2001)029<0103:COIAMF>2.0.CO;2 |bibcode=2001Geo....29..103M }}</ref>"<ref name=IoMoon/>
{{clear}}

=
[[Mimas]]=
[[Image:Mimas moon.jpg|thumb|right|200px|Herschel Crater on Saturn's moon Mimas is shown in the image. Credit: .]]
The Herschel Crater on Saturn's moon Mimas is shown in the image at right.
{{clear}}

=[[Titan]]=
[[Image:Titancrater.jpg|thumb|right|200px|This radar image of Titan shows a semi-circular feature that may be part of an impact crater. Credit: NASA/JPL-Caltech/ASI.]]
"This radar image [at right] of Titan shows a semi-circular feature that may be part of an impact crater. Very few impact craters have been seen on Titan so far, implying that the surface is young. Each new crater identified on Titan helps scientists to constrain the age of the surface."<ref name=Lavoie02162007>{{ cite web
|author=Sue Lavoie
|title=PIA09175: A New Crater on Titan?
|publisher=NASA/JPL
|location=Pasadena, California USA
|month=February 26,
|year=2007
|url=http://photojournal.jpl.nasa.gov/catalog/PIA09175
|pdf=⏎
|accessdate=2013-06-13 }}</ref>
{{clear}}

=[[Comets]]=
[[Image:Tempel Impactor 150Km.jpg|thumb|right|200px|The impactor close-up image is taken shortly before impact. Credit: NASA.]]
"'''''Deep Impact''''' is a NASA space probe launched on January 12, 2005. It was designed to study the composition of the comet interior of 9P/Tempel, by releasing an impactor into the comet. At 5:52 UTC on July 4, 2005, the impactor successfully collided with the comet's nucleus. The impact excavated debris from the interior of the nucleus, allowing photographs of the impact crater. The photographs showed the comet to be more dusty and less icy than had been expected. The impact generated a large and bright dust cloud, which unexpectedly obscured the view of the impact crater."<ref name=DeepImpactSpacecraft>{{ cite web
|title=Deep Impact (spacecraft), In: ''Wikipedia''
|publisher=Wikimedia Foundation, Inc
|location=San Francisco, California
|month=November 15,
|year=2012
|url=http://en.wikipedia.org/wiki/Deep_Impact_(spacecraft)
|accessdate=2012-12-05 }}</ref>
{{clear}}

=[[Research]]=

==Hypothesis:
# There is at least one key clue or ingredient that allows the differentiation of craters by their origins or causative factors.

==[[Control groups]]==
[[Image:Lewis rat.jpg|thumb|right|200px|This is an image of a Lewis rat. Credit: Charles River Laboratories.]]
The findings demonstrate a statistically systematic change from the ''status quo'' or the [[control group]].

“In the design of experiments, treatments [or special properties or characteristics] are applied to [or observed in] experimental units in the '''treatment group'''(s).<ref name=Hinkelmann>{{ cite book
|author=Klaus Hinkelmann, Oscar Kempthorne
|year=2008
|title=Design and Analysis of Experiments, Volume I: Introduction to Experimental Design
|url=http://books.google.com/?id=T3wWj2kVYZgC&printsec=frontcover
|edition=2nd
|publisher=Wiley
|isbn=978-0-471-72756-9
|mr=2363107 }}</ref> In ''comparative'' experiments, members of the complementary group, the '''control group''',  receive either ''no''&nbsp;treatment or a ''standard'' treatment.<ref name="Bailey">{{ cite book
|author=R. A. Bailey
|title=Design of comparative experiments
|publisher=Cambridge University Press
|url=http://www.cambridge.org/uk/catalogue/catalogue.asp?isbn=9780521683579
|year=2008 
|mr=2422352
|isbn=978-0-521-68357-9
|url1=http://www.maths.qmul.ac.uk/~rab/DOEbook/ }}</ref>"<ref name=ControlGroup>{{ cite web
|title=Treatment and control groups, In: ''Wikipedia''
|publisher=Wikimedia Foundation, Inc
|location=San Francisco, California
|month=May 18,
|year=2012
|url=http://en.wikipedia.org/wiki/Control_group
|accessdate=2012-05-31 }}</ref>
{{clear}}

==[[Proof of concept]]==

'''Def.''' a “short and/or incomplete realization of a certain method or idea to demonstrate its feasibility"<ref name=ProofofConceptWikt>{{ cite web
|title=proof of concept, In: ''Wiktionary''
|publisher=Wikimedia Foundation, Inc
|location=San Francisco, California
|month=November 10,
|year=2012
|url=http://en.wiktionary.org/wiki/proof_of_concept
|accessdate=2013-01-13 }}</ref> is called a '''proof of concept'''.

'''Def.''' evidence that demonstrates that a concept is possible is called '''proof of concept'''.

The proof-of-concept structure consists of
# background,
# procedures,
# findings, and
# interpretation.<ref name=Lehrman>{{ cite journal
|author=Ginger Lehrman and Ian B Hogue, Sarah Palmer, Cheryl Jennings, Celsa A Spina, Ann Wiegand, Alan L Landay, Robert W Coombs, Douglas D Richman, John W Mellors, John M Coffin, Ronald J Bosch, David M Margolis
|title=Depletion of latent HIV-1 infection in vivo: a proof-of-concept study
|journal=Lancet
|month=August 13,
|year=2005
|volume=366
|issue=9485
|pages=549-55
|url=http://www.sciencedirect.com/science/article/pii/S0140673605670985ncbi.nlm.nih.gov/pmc/articles/PMC1894952/
|arxiv=
|bibcode=
|doi=10.1016/S0140-6736(05)67098-5
|pmid=
|pdf=http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1894952/⏎
|accessdate=2012-05-09 }}</ref>

=See also=
{{div col|colwidth=12em}}
* [[Meteor astronomy]]
* [[Meteorites]]
{{Div col end}}

=References=
{{reflist|2}}

=Further reading=⏎
⏎
=External links=
* [http://www.ajol.info/ African Journals Online]
* [http://www.bing.com/search?q=&go=&qs=n&sk=&sc=8-15&qb=1&FORM=AXRE Bing Advanced search]
* [http://books.google.com/ Google Books]
* [http://scholar.google.com/advanced_scholar_search?hl=en&lr= Google scholar Advanced Scholar Search]
* [http://www.iau.org/ International Astronomical Union]
* [http://www.jstor.org/ JSTOR]
* [http://www.lycos.com/ Lycos search]
(contracted; show full)
* [http://cas.sdss.org/astrodr6/en/tools/quicklook/quickobj.asp SDSS Quick Look tool: SkyServer]
* [http://simbad.u-strasbg.fr/simbad/ SIMBAD Astronomical Database]
* [http://simbad.harvard.edu/simbad/ SIMBAD Web interface, Harvard alternate]
* [http://nssdc.gsfc.nasa.gov/nmc/SpacecraftQuery.jsp Spacecraft Query at NASA.]
* [http://www.springerlink.com/ SpringerLink]
* [http://www.tandfonline.com/ Taylor & Francis Online]
* [http://heasarc.gsfc.nasa.gov/cgi-bin/Tools/convcoord/convcoord.pl 
  Universal coordinate converter]
* [http://onlinelibrary.wiley.com/advanced/search Wiley Online Library Advanced Search]
* [http://search.yahoo.com/web/advanced Yahoo Advanced Web Search]

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