Difference between revisions 2117894 and 2117895 on enwikiversity

[[Image:Chain of impact craters on Ganymede.jpg|thumb|right|250px|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.

(contracted; show full)e 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==
{{main|
Keynote lectures/Mercury}}
[[Image:Mercury Globe-MESSENGER mosaic centered at 0degN-0degE.jpg|thumb|right|250px|This is a composite image of Mercury taken by the MESSENGER probe. Credit: .]]
[[Image:Mariner 10.jpg|thumb|left|250px|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
| caption1 = Mercury's Caloris Basin is one of the largest impact features in the Solar System
| image2 = Mercury weird terrain.jpg
| caption2 = The so-called "Weird Terrain" was formed at the point antipodal to the Caloris Basin impact
}}
[[Image:Stevenson crater (MESSENGER).png|thumb|right|250px|This is a MESSENGER image of catena on Mercury. Credit: NASA, JPL, APL (Jet Propulsion Laboratory).]]
Mercury's surface is heavily cratered and similar in appearance to Earth's [[Moon/Keynote lectureSpecial:Search |Moon]]. For example, an unusual crater with radiating troughs has been discovered which scientists called "the spider."<ref>{{cite book
 | author=Staff | title=Scientists see Mercury in a new light
 | url=http://www.sciencedaily.com/releases/2008/02/080201093149.htm
 | publisher=Science Daily | date=February 28, 2008
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Overall, about 15 impact basins have been identified on the imaged part of Mercury. A notable basin is the 400&nbsp;km wide, multi-ring Tolstoj Basin which has an ejecta blanket extending up to 500&nbsp;km from its rim and a floor that has been filled by smooth plains materials. Beethoven Basin has a similar-sized ejecta blanket and a 625&nbsp;km diameter rim.<ref name="Spudis01" /> Like the [[
Moon/Keynote lectureSpecial:Search |Moon]], the surface of Mercury has likely incurred the effects of space weathering processes, including Solar wind and micrometeorite impacts.<ref name=Denevi>{{ cite journal
 | title=Albedo of Immature Mercurian Crustal Materials: Evidence for the Presence of Ferrous Iron
 | journal=Lunar and Planetary Science | volume=39 | year=2008 | page=1750
 | last=Denevi | first=B. W. | coauthors=Robinson, M. S.
 | bibcode=2008LPI....39.1750D
 | last2=Robinson }}</ref>

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