Transverse Aeolian ridges (TARs)

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Transverse Aeolian ridges (TARs) are light-toned features typically found in spots on Mars, especially on the floors of channels. Thus they sever as markers for where channels are located. They were first seen in narrow-angle images from the Mars Global Surveyor Mars Orbiter Camera (MOC). Even though TARs are widespread on Mars, their formation, age, and composition are not totally understood. [1] [2] [3] [4] [5] [6] [7] [8]

Aeolian bedforms

Features that used the wind for their formation, Aeolian bedforms, are usually classified as dunes or ripple marks ( which are much smaller).[9] [10] Dunes are taller than 0.5 m or taller on Earth and usually display an asymmetrical cross section. Wind ripples are much smaller—being only 0.6 - 15 mm high. Ripples are more symmetrical in profile and are created by sand grains bouncing along: this process is called “saltation” by geologists. But, TARs are several orders of magnitude larger than wind ripples observed on Mars or Earth.[11] [12] [13] [14] [15] On Mars, TARs represent some intermediate form with characteristics of both ripple marks and dunes. [16] [17] [18] [19] [20]

Furthermore, while TARs and dunes both seem to be composed of the dark volcanic mineral basalt. TARs are generally lighter in color and have lower thermal inertias than dunes. Hard, rocky materials have a higher thermal inertia. Scientists believe that the lower thermal inertia means that the surface of TARs is composed of smaller particles than dunes. [21] [22] [23]

Although a 2020 study found evidence that some isolated TARs could still be moving a small amount, but most studies suggests they do not move.[24]

Images of TARs


  1. Berman, Daniel C.; Balme, Matthew R.; Rafkin, Scot C.R.; Zimbelman, James R. (2011). "Transverse Aeolian Ridges (TARs) on Mars II: Distributions, orientations, and ages". Icarus. 213 (1): 116–130. Bibcode:2011Icar..213..116B. doi:10.1016/j.icarus.2011.02.014. ISSN 0019-1035.
  2. Balme, Matt; Berman, Daniel C.; Bourke, Mary C.; Zimbelman, James R. (2008). "Transverse Aeolian Ridges (TARs) on Mars". Geomorphology. 101 (4): 703–720. Bibcode:2008Geomo.101..703B. doi:10.1016/j.geomorph.2008.03.011. ISSN 0169-555X.
  3. Wilson, Sharon A. (2004). "Latitude-dependent nature and physical characteristics of transverse aeolian ridges on Mars". Journal of Geophysical Research. 109 (E10): E10003. Bibcode:2004JGRE..10910003W. doi:10.1029/2004JE002247. ISSN 0148-0227.
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  6. Geissler, Paul E. (2014). "The birth and death of transverse aeolian ridges on Mars: Transverse Aeolian Ridges on Mars". Journal of Geophysical Research: Planets. 119 (12): 2583–2599. doi:10.1002/2014JE004633.
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  11. Vriend, N. M.; Jarvis, P. A. (2018). "Between a ripple and a dune". Nature Physics. 14 (7): 641–642. Bibcode:2018NatPh..14..641V. doi:10.1038/s41567-018-0113-0. ISSN 1745-2473. S2CID 125921951.
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  13. Boulton, J. Wayne (1997). Quantifying the morphology of aeolian impact ripples formed in a natural dune setting. National Library of Canada = Bibliothèque nationale du Canada. OCLC 654186636.
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  22. Fenton, Lori K.; Mellon, Michael T. (2006). "Thermal properties of sand from Thermal Emission Spectrometer (TES) and Thermal Emission Imaging System (THEMIS): Spatial variations within the Proctor Crater dune field on Mars". Journal of Geophysical Research. 111 (E6): E06014. Bibcode:2006JGRE..111.6014F. doi:10.1029/2004je002363. ISSN 0148-0227.
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  24. Silvestro, S.; Chojnacki, M.; Vaz, D. A.; Cardinale, M.; Yizhaq, H.; Esposito, F. (2020). "Megaripple Migration on Mars". Journal of Geophysical Research: Planets. 125 (8): e2020JE006446. Bibcode:2020JGRE..12506446S. doi:10.1029/2020JE006446. ISSN 2169-9097. PMC 7583471. PMID 33133993.