{{Use mdy dates|date=November 2022}} {{About|the Mars geologic system and time period|other senses|Amazonia (disambiguation){{!}}Amazonia}} {{short description|Time period on Mars}} {{Infobox geologic timespan | name = Amazonian | manual_color = rgb(255.0, 127.0, 51.0) | top_bar = mars | time_start = 2000 | time_start_prefix = | time_start_uncertainty = | time_end = 0 | time_end_prefix = | time_end_uncertainty = | earliest = 3200 | latest = | top_bar_ps = (lower bound uncertain – between about 3200 and 2000 million years ago) | image_map = | caption_map = | image_outcrop = USGS-Mars-AmazonisPlanitia-mola.jpg | caption_outcrop = [[Mars Orbital Laser Altimeter|MOLA]] colorized relief map of [[Amazonis Planitia]], the [[type locality (geology)|type area]] for the Amazonian System. Amazonis Planitia is characterized by low rates of meteorite and asteroid impacts. Colors indicate elevation, with red highest, yellow intermediate, and green/blue lowest. | image_art = | caption_art = <!--Chronology--> | timeline = | subdivisions = | proposed_subdivision1 = | proposed_subdivision1_coined = | proposed_subdivision2 = | proposed_subdivision2_coined = | proposed_subdivision3 = | proposed_subdivision3_coined = | former_subdivisions = | formerly_part_of = | partially_contained_in = | partially_contains = <!--Etymology--> | alternate_spellings = | synonym1 = | synonym1_coined = | synonym2 = | synonym2_coined = | synonym3 = | synonym3_coined = | former_names = | proposed_names = <!--Usage Information--> | celestial_body = mars | usage = | timescales_used = Martian Geologic Timescale | used_by = | formerly_used_by = | not_used_by = <!--Definition--> | chrono_unit = Period | strat_unit = System | proposed_by = | type_section = [[Amazonis Planitia]] | lower_boundary_def = | lower_stratotype_location = | upper_boundary_def = | upper_stratotype_location = <!--Atmospheric and Climatic Data--> | o2 = | co2 = | temp = | sea_level = }} The '''Amazonian''' is a [[system (stratigraphy)|geologic system]] and [[geologic timescale|time period]] on the planet [[Mars]] characterized by low rates of [[meteorite]] and [[asteroid]] [[Impact event|impacts]] and by cold, hyperarid conditions broadly similar to those on Mars today.<ref>Tanaka, K.L. (1986). The Stratigraphy of Mars. ''J. Geophys. Res.,'' Seventeenth Lunar and Planetary Science Conference Part 1, ''91''(B13), E139–E158.</ref><ref name="Carr2006">Carr, M.H. (2006), The Surface of Mars. Cambridge Planetary Science Series, Cambridge University Press.</ref> The transition from the preceding [[Hesperian]] period is somewhat poorly defined. The Amazonian is thought to have begun around 3 billion years ago, although [[error bar]]s on this date are extremely large (~500 million years).<ref>[[Stephanie C. Werner|Werner, S. C.]], and K. L. Tanaka (2011), Redefinition of the crater-density and absolute-age boundaries for the chronostratigraphic system of Mars, Icarus, 215(2), 603–607, {{doi|10.1016/j.icarus.2011.07.024}}.</ref> The period is sometimes subdivided into the Early, Middle, and Late Amazonian. The Amazonian continues to the present day.
The Amazonian period has been dominated by [[impact crater]] formation and [[Aeolian processes]] with ongoing isolated [[Volcanism on Mars|volcanism]] occurring in the [[Tharsis|Tharsis region]] and [[Cerberus Fossae]], including signs of activity as recently as a tens of thousands of years ago in the latter<ref name="ARX-20201111">{{cite journal |author=Horvath, David G. |display-authors=et al. |title=Evidence for geologically recent explosive volcanism in Elysium Planitia, Mars |journal=Icarus |year=2021 |volume=365 |article-number=114499 |doi=10.1016/j.icarus.2021.114499 |arxiv=2011.05956v1 |bibcode=2021Icar..36514499H |s2cid=226299879 }}</ref> and within the past few million years on [[Olympus Mons]], implying they may still be active but dormant in the present.<ref>{{cite web | last = Martel | first = Linda M. V. | date = January 31, 2005 | url = http://www.psrd.hawaii.edu/Jan05/MarsRecently.html | title = Recent Activity on Mars: Fire and Ice | publisher = Planetary Science Research Discoveries | access-date = July 11, 2006 }}</ref>
==Description and name origin==
The ''Amazonian'' System and Period is named after [[Amazonis Planitia]], which has a sparse crater density over a wide area. Such densities are representative of many Amazonian-aged surfaces. The [[Type locality (geology)|type area]] of the Amazonian System is in the [[Amazonis quadrangle]] (MC-8) around {{Coord|15|N|158|W|globe:Mars}}.
<timeline> ImageSize = width:800 height:50 PlotArea = left:15 right:15 bottom:20 top:5 AlignBars = early Period = from:-4500 till:0
TimeAxis = orientation:horizontal ScaleMajor = unit:year increment:500 start:-4500 ScaleMinor = unit:year increment:100 start:-4500
Colors= id:prenoachicol value:rgb(0.7,0.4,1) id:noachicol value:rgb(0.5,0.5,0.8) id:hespericol value:rgb(1,0.2,0.2) id:amazonicol value:rgb(1,0.5,0.2)
PlotData= align:center textcolor:black fontsize:8 mark:(line,black) width:25 shift:(0,-5) text:[[Amazonian_(Mars)|Amazonian]] from:-3000 till:0 color:amazonicol text:[[Hesperian]] from:-3700 till:-3000 color:hespericol text:[[Noachian]] from:-4100 till:-3700 color:noachicol text:[[Pre-Noachian]] from:start till:-4100 color:prenoachicol </timeline> {{center|<small>[[Geological history of Mars|Martian Time Periods (Millions of Years Ago)]]</small>}}
==Amazonian chronology and stratigraphy== [[Image:Lava flow and crater ejecta.JPG|right|thumb|240px|[[HiRISE]] image illustrating [[Law of superposition|superpositioning]], a principle that lets geologists determine the relative ages of surface units. The dark-toned lava flow overlies (is younger than) the light-toned, more heavily cratered terrain (older lava flow?) at right. The ejecta of the crater at center overlies both units, indicating that the crater is the youngest feature in the image.]]
Because it is the youngest of the Martian periods, the chronology of the Amazonian is comparatively well understood through traditional geological [[law of superposition|laws of superposition]] coupled to the relative dating technique of [[crater counting]]. The scarcity of craters characteristic of the Amazonian also means that unlike the older periods, fine scale (<100 m) surface features are preserved.<ref>Irwin, R.P., Tanaka, K.L., and Robbins, S.J., 2013, Distribution of Early, Middle, and Late Noachian cratered surfaces in the Martian highlands: Implications for resurfacing events and processes: Journal of Geophysical Research, v. 118, p. 278–291, {{doi|10.1002/jgre.20053}}.</ref> This enables detailed, process-orientated study of many Amazonian-age surface features of Mars as the necessary details of form of the surface are still visible.
Furthermore, the relative youth of this period means that over the past few hundred million years it remains possible to reconstruct the statistics of the orbital mechanics of the [[Sun]], [[Mars]], and [[Jupiter]] without the patterns being overwhelmed by [[Chaos theory|chaotic]] effects, and from this to reconstruct the variation of [[solar insolation]] – the amount of heat from the sun – reaching Mars through time.<ref>Laskar, J., Correia, A.C.M., Gastineau, M., Joutel, F., Levrard, B., and Robutel, P., 2004, Long term evolution and chaotic diffusion of the insolation quantities of Mars: Icarus, v. 170, no. 2, p. 343–364, {{doi|10.1016/j.icarus.2004.04.005}}.</ref> Climatic variations have been shown to occur in cycles not dissimilar in magnitude and duration to terrestrial [[Milankovich cycles]].
Together, these features – good preservation, and an understanding of the imposed solar flux – mean that much research on the Amazonian of Mars has focussed on understanding its [[Climate of Mars|climate]], and the [[geomorphology|surface]] [[sedimentology|processes]] that respond to the climate. This has included:
*[[Glaciers on Mars|glacial dynamics]] and [[Glacial landform|landforms]],<ref>Dickson, J.L., Head, J.W., III, and Marchant, D.R., 2010, 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, v. 294, no. 3–4, p. 332–342, {{doi|10.1016/j.epsl.2009.08.031}}.</ref> *the [[ice age|advance and retreat of ice]] across the planet,<ref>Head, J.W., III, Mustard, J.F., Kreslavsky, M.A., Milliken, R.E., and Marchant, D.R., 2003, Recent ice ages on Mars: Nature, v. 426, p. 797–802.</ref> *the behavior of [[Permafrost|ground ice]] and the [[periglacial]] forms which it produces,<ref>Levy, J.S., Head, J.W., III, and Marchant, D.R., 2009, Concentric crater fill in Utopia Planitia: History and interaction between glacial "brain terrain" and periglacial mantle processes: Icarus, v. 202, p. 462–476, {{doi|10.1016/j.icarus.2009.02.018}}.</ref> *[[Water on Mars|melt processes]] and small scale [[fluvial|fluvial geomorphology]],<ref>Fassett, C.I., Dickson, J.L., Head, J.W., III, Levy, J.S., and Marchant, D.R., 2010, Supraglacial and proglacial valleys on Amazonian Mars: Icarus, v. 208, no. 1, p. 86–100, {{doi|10.1016/j.icarus.2010.02.021}}.</ref><ref>Salese, F., G. Di Achille, A. Neesemann, G. G. Ori, and E. Hauber (2016), Hydrological and sedimentary analyses of well-preserved paleofluvial-paleolacustrine systems at Moa Valles, Mars, J. Geophys. Res. Planets, 121, 194–232, {{doi|10.1002/2015JE004891}}.</ref> *variation in [[Atmosphere of Mars|atmospheric properties]],<ref>Leblanc, F., and R. E. Johnson. "Role of molecular species in [[pickup ion]] sputtering of the Martian atmosphere." Journal of Geophysical Research: Planets (1991–2012) 107.E2 (2002): 5–1.</ref> *[[groundwater]] dynamics,<ref>Burr, D.M., [[JA Grier|Grier, J.A.]], McEwen, A.S., and Keszthelyi, L.P., 2002, Repeated Aqueous Flooding from the Cerberus Fossae: Evidence for Very Recently Extant, Deep Groundwater on Mars: Icarus, v. 159, no. 1, p. 53–73, {{doi|10.1006/icar.2002.6921}}.</ref> *[[ice cap]] dynamics,<ref>Kolb, Eric J., and Kenneth L. Tanaka. "Geologic history of the polar regions of Mars based on Mars Global Surveyor data: II. Amazonian Period." Icarus 154.1 (2001): 22–39.</ref> *CO<sub>2</sub> frost dynamics, and exotic surface features related to them such as "spiders"<ref>Kieffer, Hugh H., [[Philip R. Christensen]], and Timothy N. Titus. "CO2 jets formed by sublimation beneath translucent slab ice in Mars' seasonal south polar ice cap." Nature 442.7104 (2006): 793–796.</ref> *the effects of [[wind]] on deposits of [[sand]] and [[dust]] and general [[Aeolian processes|aeolian sedimentology]],<ref>Balme, Matt, et al. "Transverse aeolian ridges (TARs) on Mars." Geomorphology 101.4 (2008): 703–720.</ref><ref>Basu, Shabari, Mark I. Richardson, and R. John Wilson. "Simulation of the Martian dust cycle with the GFDL Mars GCM." Journal of Geophysical Research: Planets (1991–2012) 109.E11 (2004).</ref> *and the [[Climate model|modelling]] of [[Climate of Mars|past climate conditions]] (wind fields, temperatures, cloud properties, atmospheric chemistry) themselves.<ref>Read, Peter L., and Stephen R. Lewis. The Martian climate revisited: Atmosphere and environment of a desert planet. Springer Verlag, 2004.</ref><ref>Jakosky, Bruce M., and Roger J. Phillips. "Mars' volatile and climate history." nature 412.6843 (2001): 237–244.</ref>
Good preservation has also enabled detailed studies of other geological processes on Amazonian Mars, notably [[Volcanology of Mars|volcanic processes]],<ref>Mangold, N., et al. "A Late Amazonian alteration layer related to local volcanism on Mars." Icarus 207.1 (2010): 265–276.</ref><ref>Hartmann, William K., and Daniel C. Berman. "Elysium Planitia lava flows: Crater count chronology and geological implications." Journal of Geophysical Research: Planets (1991–2012) 105.E6 (2000): 15011–15025.</ref><ref>Neukum, Gerhard, et al. "Recent and episodic volcanic and glacial activity on Mars revealed by the High Resolution Stereo Camera." Nature 432.7020 (2004): 971–979.</ref> brittle [[tectonics]],<ref>Márquez, Álvaro, et al. "New evidence for a volcanically, tectonically, and climatically active Mars." Icarus 172.2 (2004): 573–581.</ref><ref>Mueller, Karl, and Matthew Golombek. "Compressional structures on Mars." Annu. Rev. Earth Planet. Sci. 32 (2004): 435–464.</ref> and [[Impact crater|cratering processes]].<ref>Robbins, Stuart J., and Brian M. Hynek. "Distant secondary craters from Lyot crater, Mars, and implications for surface ages of planetary bodies." Geophysical Research Letters 38.5 (2011).</ref><ref>Malin, Michael C., et al. "Present-day impact cratering rate and contemporary gully activity on Mars." science 314.5805 (2006): 1573–1577.</ref><ref>Popova, Olga, Ivan Nemtchinov, and William K. Hartmann. "Bolides in the present and past Martian atmosphere and effects on cratering processes." Meteoritics & Planetary Science 38.6 (2003): 905–925.</ref>
===System vs. Period=== {{Stratigraphy-Mars}} ''System'' and ''Period'' are not interchangeable terms in formal stratigraphic nomenclature, although they are frequently confused in popular literature. A system is an idealized stratigraphic [[Geologic record|column]] based on the physical rock record of a [[Type locality (geology)|type area]] (type section) correlated with rocks sections from many different locations planetwide.<ref name=EicherMcAlester80>Eicher, D.L.; McAlester, A.L. (1980).''History of the Earth;'' Prentice-Hall: Englewood Cliffs, NJ, pp 143–146, {{ISBN|0-13-390047-9}}.</ref> A system is bound above and below by [[stratum|strata]] with distinctly different characteristics (on Earth, usually [[index fossil]]s) that indicate dramatic (often abrupt) changes in the dominant fauna or environmental conditions. (See [[Cretaceous–Paleogene boundary]] as example.)
At any location, rock sections in a given system are apt to contain gaps ([[unconformity|unconformities]]) analogous to missing pages from a book. In some places, rocks from the system are absent entirely due to nondeposition or later erosion. For example, rocks of the [[Cretaceous]] System are absent throughout much of the eastern central interior of the United States. However, the time interval of the Cretaceous (Cretaceous Period) still occurred there. Thus, a geologic period represents the time interval over which the [[stratum|strata]] of a system were deposited, including any unknown amounts of time present in gaps.<ref name=EicherMcAlester80/> Periods are measured in years, determined by [[radioactive dating]]. On Mars, radiometric ages are not available except from [[Martian meteorites]] whose [[provenance]] and stratigraphic context are unknown. Instead, [[absolute age]]s on Mars are determined by impact crater density, which is heavily dependent upon [[Scientific modelling|models]] of crater formation over time.<ref>Masson, P.; Carr, M.H.; Costard, F.; Greeley, R.; Hauber, E.; Jaumann, R. (2001). Geomorphologic Evidence for Liquid Water. ''Space Science Reviews,'' '''96''', p. 352.</ref> Accordingly, the beginning and end dates for Martian periods are uncertain, especially for the Hesperian/Amazonian boundary, which may be in error by a factor of 2 or 3.<ref name=NimmoTanaka05>Nimmo, F.; Tanaka, K. (2005). Early Crustal Evolution of Mars. Annu. Rev. ''Earth Planet. Sci.,'' '''33''', 133–161.</ref><ref>Hartmann, W.K.; Neukum, G. (2001). Cratering Chronology and Evolution of Mars. In Chronology and Evolution of Mars, Kallenbach, R. ''et al.'' Eds., ''Space Science Reviews,'' '''96:''' 105–164.</ref>
==Images== <gallery> Image:Pedestal crater and streaks.jpg|[[Pedestal crater]] in Amazonis with Dark Slope Streaks, as seen by HiRISE. Image:Tooting Crater.JPG|Wall of [[Tooting Crater]], as seen by HiRISE. Image:Pettit Crater Rim.JPG|[[Pettit Crater]] rim, as seen by HiRISE. Image:Nicholson Crater Mound.JPG|[[Nicholson (Martian crater)|Nicholson mound]] with dark streaks, as seen by HiRISE. Image:Lycus Sulci.JPG|[[Lycus Sulci]], as seen by HiRISE. Image:Marte Vallis Island.JPG|Streamlined Island in [[Marte Vallis]], as seen by HiRISE. Image:Tartarus Colles Channel.JPG|[[Tartarus Colles]] channel, as seen by HiRISE. Image:Channels From Fissure.JPG|Channels From Fissure, as seen by HiRISE. Image:26552sharpridges.jpg|Narrow ridges, as seen by HiRISE. Image:Medusae Fossae Remnant.jpg|Plateau made up of [[Medusae Fossae Formation|Medusae Fossae]] materials and rootless cones, as seen by HiRISE. Image:26552surfaces.jpg|Surfaces in [[Amazonis quadrangle]], as seen by HiRISE. </gallery>
==See also== *[[Geological history of Mars]] *[[Geology of Mars]]
==Notes and references== {{reflist}}
==Bibliography and recommended reading== *Boyce, Joseph, M. (2008). ''The Smithsonian Book of Mars;'' Konecky & Konecky: Old Saybrook, CT, {{ISBN|978-1-58834-074-0}} *Carr, Michael, H. (2006). ''The Surface of Mars;'' Cambridge University Press: Cambridge, UK, {{ISBN|978-0-521-87201-0}}. *Hartmann, William, K. (2003). ''A Traveler's Guide to Mars: The Mysterious Landscapes of the Red Planet;'' Workman: New York, {{ISBN|0-7611-2606-6}}. *Morton, Oliver (2003). ''Mapping Mars: Science, Imagination, and the Birth of a World;'' Picador: New York, {{ISBN|0-312-42261-X}}. {{Mars}} {{Portal bar|Solar System}}
[[Category:Geologic time scale of Mars]] [[Category:Noachis quadrangle]] [[Category:Geological units]] [[Category:Articles which contain graphical timelines]]