Glaciers, loosely defined as patches of currently or recently flowing ice, are thought to be present across large but restricted areas of the modern Martian surface, and are inferred to have been more widely distributed at times in the past.[1][2] Lobate convex features on the surface known as viscous flow features and lobate debris aprons, which show the characteristics of non-Newtonian flow, are now almost unanimously regarded as true glaciers.[1][3][4][5][6][7][8][9][10] However, a variety of other features on the surface have also been interpreted as directly linked to flowing ice, such as fretted terrain[11][1], lineated valley fill[7][9], concentric crater fill,[3][12] and arcuate ridges[10]. A variety of surface textures seen in imagery of the midlatitudes and polar regions are also thought to be linked to sublimation of glacial ice.[12][13]
Today, features interpreted as glaciers are largely restricted to latitudes polewards of around 30° latitude.[14] Particular concentrations are found in the Ismenius Lacus quadrangle.[2] Based on our current models of the Martian atmosphere, ice should not however be stable if exposed at the surface in the mid-Martian latitudes.[15] It is thus thought that most glaciers must be covered with a layer of rubble or dust preventing free transfer of water vapor from the subliming ice into the air.[8][15][16] This also suggests that at in Mars' relatively recent past, its climate must have been different in order to allow the glaciers to grow stably at these latitudes.[14] This provides good independent evidence that the obliquity of Mars has changed significantly in the past, as independently indicated by modelling of Mars' orbital solutions.[17] Evidence for past glaciation also appears on the peaks of several Martian volcanoes in the tropics.[18][19][20]
Like glaciers on Earth, glaciers on Mars are not pure water ice.[1][10] Many are thought to contain substantial proportions of debris, and a substantial number are probably better described as rock glaciers.[20][21][22] For many years, largely because of the modeled instability of water ice in the midlatitudes where the putative glacial features were concentrated, it was argued that almost all glaciers were rock glaciers on Mars.[23] However, recent direct observations made by the SHARAD radar instrument on the Mars Reconnaissance Orbiter satellite have confirmed that at least some features are relatively pure ice, and thus, true glaciers.[6][8] Some authors have also made claims that glaciers of solid carbon dioxide have formed on Mars under certain rare conditions.[24]
Current glacial features on Mars
editDon't flow today?!
Viscous flow features
editLobate debris aprons
editLineated valley fill
editIce caps
editEvidence for changing glaciation through time
editArcuate ridges
editEskers
editKettle holes
editModern and past distribution of glaciers
editSee also
editReferences
edit- ^ a b c d "The Surface of Mars" Series: Cambridge Planetary Science (No. 6) ISBN 978-0-511-26688-1 Michael H. Carr, United States Geological Survey, Menlo Park
- ^ a b Hugh H. Kieffer (1992). Mars. University of Arizona Press. ISBN 978-0-8165-1257-7. Retrieved March 7, 2011.
- ^ a b Milliken, R. E., J. F. Mustard, and D. L. Goldsby. "Viscous flow features on the surface of Mars: Observations from high-resolution Mars Orbiter Camera (MOC) images." Journal of Geophysical Research 108.E6 (2003): 5057.
- ^ S.W. Squyres, M.H. Carr Geomorphic evidence for the distribution of ground ice on Mars Science, 213 (1986), pp. 249–253. doi:10.1126/science.231.4735.249
- ^ J.W. Head, D.R. Marchant, J.L. Dickson, A.M. Kress, D.M. Baker Northern mid-latitude glaciation in the Late Amazonian period of Mars: Criteria for the recognition of debris-covered glacier and valley glacier landsystem deposits Earth Planet. Sci. Lett., 294 (2010), pp. 306–320
- ^ a b J.W. Holt et al. Radar sounding evidence for buried glaciers in the southern mid-latitudes of Mars Science, 322 (2008), pp. 1235–1238
- ^ a b G.A. Morgan, J.W. Head, D.R. Marchant Lineated valley fill (LVF) and lobate debris aprons (LDA) in the Deuteronilus Mensae northern dichotomy boundary region, Mars: Constraints on the extent, age and episodicity of Amazonian glacial events Icarus, 202 (2009), pp. 22–38
- ^ a b c J.J. Plaut, A. Safaeinili, J.W. Holt, R.J. Phillips, J.W. Head, R. Sue, N.E. Putzig, A. Frigeri Radar evidence for ice in lobate debris aprons in the mid-northern latitudes of Mars Geophys. Res. Lett., 36 (2009), p. L02203
- ^ a b D.M.H. Baker, J.W. Head, D.R. Marchant Flow patterns of lobate debris aprons and lineated valley fill north of Ismeniae Fossae, Mars: Evidence for extensive mid-latitude glaciation in the Late Amazonian Icarus, 207 (2010), pp. 186–209
- ^ a b c J. Arfstrom, W.K. Hartmann Martian flow features, moraine-like ridges, and gullies: Terrestrial analogs and interrelationships Icarus, 174 (2005), pp. 321–335
- ^ Lucchitta, Baerbel K. "Ice and debris in the fretted terrain, Mars." Journal of Geophysical Research: Solid Earth (1978–2012) 89.S02 (1984): B409-B418.
- ^ a b Levy, Joseph S., James W. Head, and David R. Marchant. "Concentric crater fill in Utopia Planitia: History and interaction between glacial “brain terrain” and periglacial mantle processes." Icarus 202.2 (2009): 462-476.Levy, Joseph S., James W. Head, and David R. Marchant. "Concentric crater fill in Utopia Planitia: History and interaction between glacial “brain terrain” and periglacial mantle processes." Icarus 202.2 (2009): 462-476.
- ^ Hubbard, Bryn, et al. "Geomorphological characterisation and interpretation of a mid-latitude glacier-like form: Hellas Planitia, Mars." Icarus 211.1 (2011): 330-346.
- ^ a b Head, J. W., et al. "Extensive valley glacier deposits in the northern mid-latitudes of Mars: Evidence for Late Amazonian obliquity-driven climate change." Earth and Planetary Science Letters 241.3 (2006): 663-671.
- ^ a b Williams, K. E., et al. "Stability of mid-latitude snowpacks on Mars." Icarus 196.2 (2008): 565-577.
- ^ Head, J.; Neukum, G.; Jaumann, R.; Hiesinger, H.; Hauber, E.; Carr, M.; Masson, P.; Foing, B.; Hoffmann, H. (2005). "Tropical to mid-latitude snow and ice accumulation, flow and glaciation on Mars". Nature. 434 (7031): 346–350. Bibcode:2005Natur.434..346H. doi:10.1038/nature03359. PMID 15772652.
- ^ Laskar, Jacques, et al. "Long term evolution and chaotic diffusion of the insolation quantities of Mars." Icarus 170.2 (2004): 343-364.
- ^ Head, J. W., et al. "Tropical to mid-latitude snow and ice accumulation, flow and glaciation on Mars." Nature 434.7031 (2005): 346-351.
- ^ Shean, David E. (2005). "Origin and evolution of a cold-based tropical mountain glacier on Mars: The Pavonis Mons fan-shaped deposit". Journal of Geophysical Research. 110. Bibcode:2005JGRE..11005001S. doi:10.1029/2004JE002360.
- ^ a b Head, James W., and David R. Marchant. "Cold-based mountain glaciers on Mars: western Arsia Mons." Geology 31.7 (2003): 641-644.
- ^ Colaprete, Anthony, and Bruce M. Jakosky. "Ice flow and rock glaciers on Mars." Journal of Geophysical Research: Planets (1991–2012) 103.E3 (1998): 5897-5909.
- ^ Haeberli, Wilfried, et al. "Permafrost creep and rock glacier dynamics." Permafrost and Periglacial Processes 17.3 (2006): 189-214.
- ^ Squyres, Steven W. "Martian fretted terrain: Flow of erosional debris." Icarus 34.3 (1978): 600-613.
- ^ Kreslavsky, Mikhail A., and James W. Head. "Carbon dioxide glaciers on Mars: Products of recent low obliquity epochs (?)." Icarus 216.1 (2011): 111-115.