A concentric crater fill (CCF) is a landform where the floor of a crater is mostly covered with many parallel ridges. It is common in the mid-latitudes of Mars,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. and is widely believed to be caused by glacial movement.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.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. Areas on Mars called Deuteronilus Mensae and Protonilus Mensae contain many examples of concentric crater fill.
Description
Concentric crater fill, like lobate debris aprons and lineated valley fill, is believed to be ice-rich.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. 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.Marchant, D. et al. 2002. Formation of patterned ground and sublimation till over Miocene glacier ice in Beacon valley, southern Victorialand, Antarctica. Geol. Soc. Am. Bull:114. 718-730.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. 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 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.Mellon, M. 1997. Small-scale polygonal features on Mars: Seasonal thermal contraction cracks in permafrost. J. Geophysical Res: 102. 25,617-625,628.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.
See also
References