{{short description|Physical evolution of the planet Mars}} [[File:Lava flow and crater ejecta.JPG|thumb|right|HiRISE image illustrating Steno's [[law of superposition]]. The dark-toned [[lava]] flow overlies (is younger than) the light-toned terrain at right. The ejecta of the crater at centre overlies both units, indicating that the crater is younger than both units.]]
The '''geological history of Mars''' follows the physical evolution of [[Mars]] as substantiated by observations, indirect and direct measurements, and various inference techniques. Methods dating back to 17th-century techniques developed by [[Nicholas Steno]], including the so-called [[law of superposition]] and [[stratigraphy]], used to estimate the geological histories of Earth and the Moon, are being actively applied to the data available from several Martian observational and measurement resources. These include landers, orbiting platforms, Earth-based observations, and [[Martian meteorite]]s.
Observations of the surfaces of many [[Solar System]] bodies reveal important clues about their evolution. For example, a lava flow that spreads out and fills a large impact crater is likely to be younger than the crater. On the other hand, a small crater on top of the same lava flow is likely to be younger than both the lava and the larger crater since it can be surmised to have been the product of a later, unobserved, geological event. This principle, called the [[law of superposition]], along with other principles of [[stratigraphy]] first formulated by [[Nicholas Steno]] in the 17th century, allowed geologists of the 19th century to divide the history of the Earth into the familiar eras of [[Paleozoic]], [[Mesozoic]], and [[Cenozoic]]. The same methodology was later applied to the [[Moon]]<ref>For reviews of this topic, see: *{{cite book |last=Mutch |first=T. A. |year=1970 |title=Geology of the Moon: A Stratigraphic View |publisher=Princeton University Press |location=Princeton, New Jersey}} *{{cite book |last=Wilhelms |first=D. E. |year=1987 |title=The Geologic History of the Moon |bibcode=1987ghm..book.....W |id=USGS Professional Paper 1348 |url=http://ser.sese.asu.edu/GHM/}}</ref> and then to Mars.<ref>{{cite book |last1=Scott |first1=D. H. |last2=Carr |first2=M. H. |year=1978 |title=Geologic Map of Mars |id=Miscellaneous Investigations Set Map 1-1083 |publisher=[[United States Geological Survey]] |location=Reston, Virginia}}</ref>
Another stratigraphic principle used on planets where impact craters are well preserved is that of crater number density. The number of craters greater than a given size per unit surface area (usually a million km<sup>2</sup>) provides a relative age for that surface. Heavily cratered surfaces are old, and sparsely cratered surfaces are young. Old surfaces have many big craters, and young surfaces have mostly small craters or none at all. These stratigraphic concepts form the basis for the Martian geologic timescale.
== Relative ages from stratigraphy == Stratigraphy establishes the relative ages of layers of rock and sediment by denoting differences in composition (solids, liquids, and trapped gasses). Assumptions are often incorporated about the rate of deposition, which generates a range of potential age estimates across any set of observed sediment layers.
== Absolute ages == On Earth, the primary method for calibrating geological ages to a [[calendar]] is [[radiometric dating]]. Combining the constraints from multiple different [[radioisotope]] systems can improve the precision in an age estimate. Using [[stratigraphic]] principles, the ages of [[geological unit]]s can usually only be determined [[relative dating|relative to each other]]. For example, Mesozoic rock [[stratum|strata]] making up the [[Cretaceous]] [[system (stratigraphy)|system]] lie on top of rocks of the [[Jurassic]] system, so the Cretaceous is more recent than the Jurassic. However, this tells us nothing about how long ago either the Cretaceous or Jurassic periods were, only their relative order. Absolute ages from radiometric dating are required to calibrate the stratigraphic sequence. This requires laboratory analysis of physical samples retrieved from locations with known stratigraphy, which is generally only possible for rocks on Earth. A small number of absolute ages have also been determined for rock units on the Moon, from which [[sample return mission|samples have been returned to Earth]]. Lunar relative ages are provided by [[crater counting]]. Although the number of calibration points is small, this has allowed the derivation of [[lunar geologic timescale|an approximate dating system for the Moon]].
Assigning absolute ages to rock units on Mars is far more problematic. Numerous attempts<ref>{{cite journal | doi = 10.1126/science.194.4272.1381 | last1 = Neukum | first1 = G. | last2 = Wise | first2 = D.U. | date = 1976 | title = Mars: A Standard Crater Curve and Possible New Time Scale | journal = Science | volume = 194 | issue = 4272| pages = 1381–1387 | pmid = 17819264 |bibcode = 1976Sci...194.1381N }}</ref><ref>{{cite journal | doi = 10.1029/JB086iB04p03097 | last1 = Neukum | first1 = G. | last2 = Hiller | first2 = K. | date = 1981 | title = Martian ages | journal = J. Geophys. Res. | volume = 86 | issue = B4| pages = 3097–3121 | bibcode=1981JGR....86.3097N| doi-access = free }}</ref><ref>{{cite book |last1=Hartmann |first1=W. K. |last2=Neukum |first2=G. |date=2001 |chapter=Cratering Chronology and Evolution of Mars |title=Chronology and Evolution of Mars |editor-last=Kallenbach |editor-first=R. |display-editors=etal |series=Space Science Reviews |volume=12 |pages=105–164 |isbn=0792370511 }}</ref> have been made over the years to determine an absolute Martian [[chronology]] (timeline) by comparing estimated impact cratering rates for Mars to those on the Moon. If the rate of impact crater formation on Mars by crater size per unit area over geologic time (the production rate or flux) is known with precision, then crater densities also provide a way to determine absolute ages.<ref>{{cite journal | last1 = Hartmann | first1 = W.K. | date = 2005 | title = Martian Cratering 8: Isochron Refinement and the Chronology of Mars | journal = Icarus | volume = 174 | issue = 2| page = 294 | bibcode = 2005Icar..174..294H | doi = 10.1016/j.icarus.2004.11.023 }}</ref> Unfortunately, practical difficulties in crater counting<ref>{{cite journal | doi = 10.1016/j.icarus.2007.02.011 | last1 = Hartmann | first1 = W.K. | date = 2007 | title = Martian cratering 9: Toward Resolution of the Controversy about Small Craters | journal = Icarus | volume = 189 | issue = 1| pages = 274–278 | bibcode=2007Icar..189..274H}}</ref> and uncertainties in estimating the flux still create huge uncertainties in the ages derived from these methods. Martian meteorites have provided datable samples that are consistent with ages calculated thus far,<ref>{{harvnb|Hartmann|2003|p=35}}</ref> but the locations on Mars from where the meteorites came (provenance) are unknown, limiting their value as [[chronostratigraphic]] tools. Absolute ages determined by crater density should therefore be taken with some skepticism.<ref>{{harvnb|Carr|2006|p=40}}</ref> [[File:PIA26203-Mars-HorizonViews-OdysseyTHEMIS-20230509.webm|thumb|center|600px|<div align="center">Mars - horizon views (video; 1:24; [[2001 Mars Odyssey|Odyssey orbiter]]; [[Thermal Emission Imaging System|THEMIS camera]]; 9 May 2023)</div>]]
== Crater density timescale == Studies of [[impact crater]] densities on the Martian surface<ref>Tanaka, K. L. (1986). "The Stratigraphy of Mars". ''Journal of Geophysical Research'', Seventeenth Lunar and Planetary Science Conference Part 1, ''91''(B13), E139–E158.</ref> <ref>Melosh, H.J., 2011. Planetary surface processes. Cambridge Univ. Press., pp. 500</ref> have delineated four broad [[period (geology)|periods]] in the planet's [[geological timescale|geologic history]].<ref>{{Cite web|last=Caplinger|first=Mike|title=Determining the age of surfaces on Mars|url=http://www.msss.com/http/ps/age2.html|access-date=2007-03-02|archive-url=https://web.archive.org/web/20070219192450/http://www.msss.com/http/ps/age2.html|archive-date=February 19, 2007|url-status=dead}}</ref> The periods were named after places on Mars that had large-scale surface features, such as large craters or widespread lava flows, that date back to these time periods. The absolute ages given here are only approximate. From oldest to youngest, the time periods are:
*{{anchor|Pre-Noachian|Pre-Noachian Period}}'''[[Pre-Noachian]]''': the interval from the accretion and differentiation of the planet about 4.5 billion years ago ([[Gya (unit)|Gya]]) to the formation of the [[Hellas Planitia|Hellas impact basin]], between 4.1 and 3.8 Gya.<ref>{{cite journal | last1 = Carr | first1 = M. H. | last2 = Head | first2 = J. W. | date = 2010 | title = Geologic History of Mars | url =https://zenodo.org/record/1258929 | journal = Earth and Planetary Science Letters | volume = 294 | issue = 3–4| pages = 185–203 |bibcode = 2010E&PSL.294..185C |doi = 10.1016/j.epsl.2009.06.042 }}</ref> Most of the geologic record of this interval has been erased by subsequent erosion and high impact rates. The [[Martian dichotomy|crustal dichotomy]] is thought to have formed during this time, along with the [[Argyre Planitia|Argyre]] and [[Isidis Planitia|Isidis]] basins.
[[File:Artist’s impression of Mars four billion years ago.jpg|thumb|Artist's impression of Mars four billion years ago]]
*{{anchor|Noachian|Noachian Period}}'''[[Noachian|Noachian Period]]''' (named after [[Noachis Terra]]): Formation of the oldest extant surfaces of Mars between 4.1 and about 3.7 Gya. Noachian-aged surfaces are scarred by many large impact craters. The [[Tharsis bulge]] is thought to have formed during the Noachian, along with extensive erosion by liquid water producing river [[Valley networks (Mars)|valley networks]]. Large lakes or oceans may have been present. *{{anchor|Hesperian|Hesperian Period}}'''[[Hesperian|Hesperian Period]]''' (named after [[Hesperia Planum]]): 3.7 to approximately 3.0 Gya. It is marked by the formation of extensive lava plains. The formation of [[Olympus Mons]] probably began during this period.<ref>{{cite journal | last1=Fuller | first1=Elizabeth R. | last2=Head | first2=James W. | title=Amazonis Planitia: The role of geologically recent volcanism and sedimentation in the formation of the smoothest plains on Mars | doi=10.1029/2002JE001842 | date=2002 | issue=E10 | pages=5081 | volume=107 | journal=Journal of Geophysical Research | bibcode=2002JGRE..107.5081F | doi-access=free }}</ref> Catastrophic releases of water carved out extensive outflow channels around Chryse Planitia and elsewhere. Ephemeral lakes or seas may have formed in the northern lowlands. *{{anchor|Amazonian Period}}'''[[Amazonian (Mars)|Amazonian Period]]''' (named after [[Amazonis Planitia]]): 3.0 Gya to present. Amazonian regions have few meteorite impact craters but are otherwise quite varied. Lava flows, glacial/[[periglacial]] activity, and minor releases of liquid water continued during this period.<ref>{{cite journal |last1=Salese |first1=F. |first2=G. |last2=Di Achille |first3=A. |last3=Neesemann |first4=G. G. |last4=Ori |first5=E. |last5=Hauber |year=2016 |title=Hydrological and sedimentary analyses of well-preserved paleofluvial-paleolacustrine systems at Moa Valles, Mars |journal=Journal of Geophysical Research: Planets |volume=121 |issue=2 |pages=194–232 |doi=10.1002/2015JE004891|bibcode=2016JGRE..121..194S |doi-access=free }}</ref>
{{Mars timescale}}
The date of the Hesperian/Amazonian boundary is particularly uncertain and could range anywhere from 3.0 to 1.5 Gya.<ref>{{harvnb|Hartmann|2003|p=34}}</ref> Basically, the Hesperian is thought of as a transitional period between the end of heavy bombardment and the cold, dry Mars seen today.
== Mineral alteration timescale == In 2006, researchers using data from the OMEGA Visible and Infrared Mineralogical Mapping Spectrometer on board the [[Mars Express]] orbiter proposed an alternative Martian timescale based on the predominant type of mineral alteration that occurred on Mars due to different styles of chemical [[weathering]] in the planet's past. They proposed dividing the history of Mars into three eras: the Phyllocian, Theiikian and Siderikan.<ref>{{Cite web|last=Williams|first=Chris|title=Probe reveals three ages of Mars|website=[[The Register]] |url=https://www.theregister.co.uk/2006/04/21/three_mars_eras/|access-date=2007-03-02 }}</ref><ref>{{Cite journal|author5-link=Raymond Arvidson|author3-link=John F. Mustard|last1=Bibring|first1=Jean-Pierre|date=2006|title=Global Mineralogical and Aqueous Mars History Derived from OMEGA/Mars Express Data|journal=Science|volume=312|issue=5772|pages=400–404|doi=10.1126/science.1122659|pmid=16627738|last2=Langevin|first2=Y|last3=Mustard|first3=JF|last4=Poulet|first4=F|last5=Arvidson|first5=R|last6=Gendrin|first6=A|last7=Gondet|first7=B|last8=Mangold|first8=N|last9=Pinet|first9=P |last10=Forget|first10=F|last11=Berthé|first11=M|last12=Bibring|first12=J. P.|last13=Gendrin|first13=A|last14=Gomez|first14=C|last15=Gondet|first15=B|last16=Jouglet|first16=D|last17=Poulet|first17=F|last18=Soufflot|first18=A|last19=Vincendon|first19=M|last20=Combes|first20=M|last21=Drossart|first21=P|last22=Encrenaz|first22=T|last23=Fouchet|first23=T|last24=Merchiorri|first24=R|last25=Belluci|first25=G|last26=Altieri|first26=F|last27=Formisano|first27=V|last28=Capaccioni|first28=F|last29=Cerroni|first29=P|last30=Coradini|first30=A|bibcode = 2006Sci...312..400B |display-authors=8|doi-access=free}}</ref>
*The '''Phyllocian''' (named after [[:Category:Phyllosilicates|phyllosilicate]] or clay minerals that characterize the era) lasted from the formation of the planet until around the Early Noachian (about 4.0 Gya). OMEGA identified outcroppings of phyllosilicates at numerous locations on Mars, all in rocks that were exclusively Pre-Noachian or Noachian in age (most notably in rock exposures in [[Nili Fossae]] and [[Mawrth Vallis]]). Phyllosillicates require a water-rich, alkaline environment to form. The Phyllocian era correlates with the age of [[Valley networks (Mars)|valley network]] formation on Mars, suggesting an early climate that was conducive to the presence of abundant surface water. It is thought that deposits from this era are the best candidates in which to search for evidence of past life on the planet. *The '''Theiikian''' (named after sulphurous in Greek, for the [[:Category:Sulfate minerals|sulphate minerals]] that were formed) lasted until about 3.5 Gya. It was an era of extensive [[volcanism]], which released large amounts of [[sulfur dioxide|sulphur dioxide]] (SO<sub>2</sub>) into the atmosphere. The SO<sub>2</sub> combined with water to create a sulphuric acid-rich environment that allowed the formation of hydrated sulphates (notably [[kieserite]] and [[gypsum]]). *The '''Siderikan''' (named for iron in Greek, for the iron oxides that formed) lasted from 3.5 Gya until the present. With the decline of volcanism and available water, the most notable surface weathering process has been the slow oxidation of the iron-rich rocks by atmospheric [[peroxide]]s producing the red [[iron oxide]]s that give the planet its familiar colour.
<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:sidericol value:rgb(1,0.4,0.3) id:theiicol value:rgb(1,0.2,0.5) id:phyllocol value:rgb(0.7,0.4,1)
PlotData= align:center textcolor:black fontsize:8 mark:(line,black) width:25 shift:(0,-5)
text:Siderikan from:-3500 till:0 color:sidericol text:Theiikian from:-4000 till:-3500 color:theiicol text:Phyllocian from:start till:-4000 color:phyllocol </timeline>
== References == {{Reflist|30em}}
{{Refbegin}}
=== Citations === * {{cite book |last=Carr |first=Michael, H. |year=2006 |title=The Surface of Mars |publisher=Cambridge University Press |isbn=978-0-521-87201-0}} * {{cite book |last=Hartmann |first=William, K. |year=2003 |title=A Traveler's Guide to Mars: The Mysterious Landscapes of the Red Planet |location=New York |publisher=Workman |isbn=0-7611-2606-6}} {{Refend}}
==External links== * [https://pubs.usgs.gov/sim/3292/ Mars - Geologic Map] ([[USGS]], 2014) ([https://pubs.usgs.gov/sim/3292/pdf/sim3292_map.pdf original] / [[:File:USGS-MarsMap-sim3292-20140714-crop.png|crop]] / [[:File:USGS-MarsMap-sim3292-20140714-full.png|full]] / [https://www.youtube.com/watch?v=quZMhSohIEU video (00:56)]). {{Mars}} {{Geography of Mars}} {{Portal bar|Solar System}}
[[Category:Geology of Mars]] [[Category:Mars timelines]] [[Category:Articles which contain graphical timelines]] [[Category:Articles containing video clips]] [[Category:Geology timelines]]