View source for Astronomy:Concentric crater fill

{{short description|Landform where the floor of a crater is mostly covered by parallel ridges}}
A '''concentric crater fill''' (CCF)<ref>{{cite journal |last1=Levy |first1=Joseph |last2=Head |first2=James W. |last3=Marchant |first3=David R. |title=Concentric crater fill in the northern mid-latitudes of Mars: Formation processes and relationships to similar landforms of glacial origin |journal=Icarus |date=October 2010 |volume=209 |issue=2 |pages=390–404 |doi=10.1016/j.icarus.2010.03.036 |bibcode=2010Icar..209..390L |url=https://www.researchgate.net/publication/222819718 |access-date=3 November 2021}}</ref> is a landform where the floor of a crater is mostly covered with many parallel ridges.<ref>{{Cite web |url=http://hiroc.lpl.arizona.edu/images/PSP/diafotizo.php?ID=PSP_111926_2185 |title=HiRISE &#124; <br/> '''Notice''': Undefined variable: Title in '''/Data/Www_hirise/Hiroc.LPL.arizona.edu/Images/PSP/Diafotizo.PHP''' on line '''23'''<br/> |access-date=2010-08-01 |archive-url=https://web.archive.org/web/20161001224229/http://hiroc.lpl.arizona.edu/images/PSP/diafotizo.php?ID=PSP_111926_2185 |archive-date=2016-10-01 |url-status=dead }}</ref>  It is common in the mid-latitudes of Mars,<ref>Dickson, J. et al.  2009.  Kilometer-thick ice accumulation and glaciation in the northern mid-latitudes of Mars:  Evidence for crater-filling events in the Late Amazonian at the Phlegra Montes.  Earth and Planetary Science Letters.</ref><ref>{{cite web|url=http://hirise.lpl.arizona.edu/PSP_001926_2185|title=HiRISE - Concentric Crater Fill in the Northern Plains (PSP_001926_2185)|website=hirise.lpl.arizona.edu}}</ref> and is widely believed to be caused by glacial movement.<ref>Head, J. et al.  2006.  Extensive valley glacier deposits in the northern mid-latitudes of Mars:  Evidence for late Amazonian obliquity-driven climate change.  Earth Planet. Sci Lett: 241.  663-671.</ref><ref>Levy, J. et al.  2007.  Lineated valley fill and lobate debris apron stratigraphy in Nilosyrtis Mensae, Mars:  Evidence for phases of glacial modification of the dichotomy boundary.  J. Geophys. Res.:  112.</ref> Areas on Mars called [[Astronomy:Deuteronilus Mensae|Deuteronilus Mensae]] and [[Astronomy:Protonilus Mensae|Protonilus Mensae]] contain many examples of concentric crater fill.

==Description==

Concentric crater fill, like lobate debris aprons and [[Astronomy:Lineated valley fill|lineated valley fill]], is believed to be ice-rich.<ref>Levy, J. et al.  2009.  Concentric crater fill in Utopia Planitia:  History and interaction between glacial "brain terrain" and periglacial processes.  Icarus: 202. 462-476.</ref>  Sometimes boulders are found on concentric crater fill; it is believed they fell off the crater wall, then were transported away from the wall with the movement of the glacier.<ref>Marchant, D. et al.  2002.  Formation of patterned ground and sublimation till over Miocene glacier ice in Beacon valley, southern Victorialand, [[Earth:Antarctica|Antarctica]].  Geol. Soc. Am. Bull:114.  718-730.</ref><ref>Head, J. and D. Marchant.  2006.  Modification of the walls of a Noachian crater in northern Arabia Terra (24E, 39N) during mid-latitude Amazonian glacial epochs on Mars:  Nature and evolution of lobate debris aprons and their relationships to lineated valley fill and glacial systems.  Lunar Planet. Sci: 37.  Abstract # 1126.</ref> [[Earth:Glacial erratic|Erratics]] on Earth were carried by similar means.

High resolution pictures taken with HiRISE reveal that some of the surfaces of concentric crater fill are covered with strange patterns called closed-cell and open-cell [[Astronomy:Brain terrain|brain terrain]].  The terrain resembles a human brain.  It is believed to be caused by cracks in the surface accumulating dust and other debris, together with ice sublimating from some of the surfaces.  The cracks are the result of stress from gravity and seasonal heating and cooling.<ref>Mellon, M.  1997.  Small-scale polygonal features on Mars:  Seasonal thermal contraction cracks in permafrost.  J. Geophysical Res: 102. 25,617-625,628.</ref><ref>Ley, J. et al.  2009.  Concentric crater fill in Utopia Planitia:  History and interaction between glacial "brain terrain" and periglacial processes.  Icarus: 202.  462-476.</ref>

<gallery class="center"  widths="190px" heights="180px" >
File:25246brainseroding.jpg|Closed-cell brain terrain, as seen by HiRISE under the HiWish program.  This type of surface is common on lobate debris aprons, concentric crater fill, and lineated valley fill.
File:Htalk23815 2215lvfclose.jpg|Open and closed-cell brain terrain, as seen by HiRISE, under HiWish program.
</gallery>
<gallery class="center"  widths="190px" heights="180px" >
Wikiconcentric.jpg|Crater showing concentric crater fill, as seen by CTX (on [[Astronomy:Mars Reconnaissance Orbiter|Mars Reconnaissance Orbiter]]).  Location is [[Astronomy:Phaethontis quadrangle|Phaethontis quadrangle]].
Wikiconcentricclose22451.jpg|Close-up view of concentric crater fill, as seen by HiRISE under HiWish program Note: this is an enlargement of previous image of a concentric crater.  Location is [[Astronomy:Phaethontis quadrangle|Phaethontis quadrangle]].

Image:Concentric Crater Fill Wide-view.jpg|Wide-view of concentric crater fill, as seen by HiRISE.  Location is the [[Astronomy:Casius quadrangle|Casius quadrangle]].
Image:Concentric Crater Fill Close-up.JPG|Concentric Crater Fill Close-up of near the top of previous image.  The surface debris covers water ice.

Wikiconcentrib22.jpg|Crater with concentric crater fill, as seen by CTX (on Mars Reconnaissance Orbiter). Location is Casius quadrangle.
Image:Hollows as seen by hirise under hiwish program.jpg|Well-developed hollows, as seen by HiRISE under the [[Astronomy:HiWish program|HiWish program]].  Location is the Casius quadrangle.  Note: this is an enlargement of the previous image that was taken by CTX.

Image:crackswithpitsconcentric.jpg|Close-up showing cracks containing pits on the floor of a crater containing concentric crater fill, as seen by HiRISE under HiWish program.  Location is the Casius quadrangle.
Image:pitscrater23035.jpg|Close-up showing cracks containing pits on the floor of a crater, as seen by HiRISE under HiWish program.  Cracks may start as a line of pits that enlarge, then join.  Location is the Casius quadrangle.
File:Ccffigurecaptioned.jpg|This series of drawings illustrates why researchers believe many craters are full of ice-rich material.  The depth of craters can be predicted based upon the observed diameter.  Many craters are almost full, rather than bowl-shaped; hence it is believed that material has accumulated within the bowls in the time since they were formed by impact.  Much of the extra material is believed to be ice that fell from the sky as snow or ice-coated dust.
</gallery>

<gallery class="center" widths="190px" heights="180px" >
File:46622 1365ctxcontextccf.jpg|Wide view of concentric crater fill, as seen by CTX Location is the [[Astronomy:Phaethontis quadrangle|Phaethontis quadrangle]].

File:46622 1365contextccf.jpg|Concentric crater fill, as seen by HiRISE under HiWish program. Location is the Phaethontis quadrangle.

File:ESP 046622 1365ccfclosecolor.jpg|Close, color view of concentric crater fill, as seen by HiRISE under HiWish program Location is the Phaethontis quadrangle.
</gallery>

== See also ==
* {{annotated link|Astronomy:Casius quadrangle}} 
* {{annotated link|Astronomy:Climate of Mars}}
* {{annotated link|Astronomy:Deuteronilus Mensae}} 
* {{annotated link|Astronomy:Fretted terrain}}
* {{annotated link|Astronomy:Impact crater}}
* {{annotated link|Earth:Glacier}}
* {{annotated link|Astronomy:Glaciers on Mars}}
* {{annotated link|Astronomy:Protonilus Mensae}} 
* {{annotated link|Astronomy:Water on Mars}}

==References==
{{reflist}}

{{Geography of Mars|geology}}

[[Category:Surface features of Mars]]

{{Sourceattribution|Concentric crater fill}}