Pre-Noachian

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Pre-Noachian
4500 – 4100 Ma
lowlands representing the Pre-Noachian landscape, alongside higher terrain indicative of the Noachian era.
Usage information
Celestial bodyMars
Time scale(s) usedMartian Geologic Timescale

The Pre-Noachian is a

subsurface water.[1] This era represents a crucial phase in Mars' history, witnessing the planet's formation, and the shaping of its geological landscape. However, the Pre-Noachian period remains elusive, being the least understood among Mars' four geological phases. Erosion and deposition
have obscured much of the evidence from this time period on Mars.

The Pre-Noachian period created

northern hemisphere of Mars, potentially serving as reservoirs for ancient Martian water during later periods. These lowlands might have formed through lava erosion caused by extensive volcanic activity during this era, as the Pre-Noachian time period experienced the highest level of volcanic activity among all Martian epochs.[1]

During the Pre-Noachian period,

oceans across Mars during subsequent time periods.[1] Over time, the gases retained by Mars' gravity during the Pre-Noachian period have gradually outgassed from the planet's atmosphere. This occurs as the molecules become too heavy and dense to be contained in a cooler environment, leading to their release into space.[1]

During this time, Mars had a distinct magnetic field because its core was active. As magma cooled in the planet's lower layers, it formed metals necessary to make the magnetic field.[3]

Description and name origin

The Pre-Noachian System and Period is named after

basin, and the pre comes from the word meaning before.[4] (See Description and name origin on the Wikipedia page for the Noachian
era on Mars for more information)

Pre-Noachian chronology and stratigraphy

Schematic cross section of image at left. Surface units are interpreted as a sequence of layers (strata), with the youngest at top and oldest at bottom in accordance with the law of superposition.
HiRISE image illustrating 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 at right. The ejecta of the crater at center overlies both units, indicating that the crater is the youngest feature in the image. (See cross section, above right.)

Martian time periods are based on

formation) representing a sheetlike, wedgelike, or tabular body of rock that underlies the surface.[6][7] A surface unit may be a crater ejecta deposit, lava flow, or any surface that can be represented in three dimensions as a discrete stratum bound above or below by adjacent units (illustrated right). Using principles such as superpositioning (illustrated left), cross-cutting relationships, and the relationship of impact crater density to age, geologists can place the units into a relative age sequence from oldest to youngest. Units of similar age are grouped globally into larger, time-stratigraphic (chronostratigraphic) units, called systems. For Mars, four systems are defined: the Pre-Noachian Noachian, Hesperian, and Amazonian. Geologic units lying below (older than) the Noachian are informally designated Pre-Noachian.[8] The geologic time (geochronologic
) equivalent of the Pre-Noachian System is the Pre-Noachian Period. Rock or surface units of the Pre-Noachian System were formed or deposited during the Pre-Noachian Period.

System vs. Period

e  h
Segments of rock (strata) in chronostratigraphy Periods of time in geochronology Notes (Mars)
Eonothem
Eon
 not used for Mars
Erathem
Era
 not used for Mars
System
Period
 3 total; 108 to 109 years in length
Series
Epoch
 8 total; 107 to 108 years in length
Stage
Age
 not used for Mars
Chronozone
Chron
 smaller than an age/stage; not used by the ICS timescale

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

index fossils) 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 (

absolute ages on Mars are determined by impact crater density, which is heavily dependent upon models of crater formation over time.[11] 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.[8][12]

Boundaries and subdivisions

The lower boundary of the Pre-Noachian period on Mars is characterized by the emergence of significant geological activity and the initial shaping of the planet's surface during its early history. This boundary is defined by the presence of ancient cratered terrains, volcanic constructs, and impact ejecta deposits dating back to the earliest stages of Martian geological development. While the precise location of this boundary may vary depending on geological context and criteria used for its definition, it marks the beginning of Mars’ geological history as understood by scientists.

In the Pre-Noachian period, the eastern region of Mars featured ridged plains overlaying early to mid-Noachian aged cratered plateau materials. This period marked a significant phase in Mars’ geological history, preceding the Noachian era characterized by its own distinct geological features and processes.

The Pre-Noachian System is subdivided into two chronostratigraphic

Epochs. It's important to note that an epoch is a subdivision of a period, and the terms are not synonymous in formal stratigraphy. The age of the Early Pre-Noachian/Late Pre-Noachian boundary remains uncertain, with estimates ranging from 4500 to 4100 million years ago based on crater counts.[13][14]

Stratigraphic terms are often confusing to geologists and non-geologists alike. One way to sort through the difficulty is by the following example: You can easily go to

Cincinnati, Ohio and visit a rock outcrop in the Upper Ordovician Series of the Ordovician System. You can even collect a fossil trilobite
there. However, you cannot visit the Late Ordovician Epoch in the Ordovician Period and collect an actual trilobite.

The Earth-based scheme of formal stratigraphic nomenclature has been successfully applied to Mars for several decades now but has numerous flaws. The scheme will no doubt become refined or replaced as more and better data become available.[15] (See mineralogical timeline below as example of alternative.) Obtaining radiometric ages on samples from identified surface units is clearly necessary for a more complete understanding of Martian history and chronology.[16]

Mars during the Pre-Noachian Period

While not directly depicting Mars, this image serves as an illustration of the possible appearance of Mars during the Pre-Noachian period.

During the Pre-Noachian period, Mars experienced significant geological and environmental dynamics. Intense volcanic activity sculpted the planet's surface through widespread eruptions, while impact cratering events left behind numerous craters across the

water bodies such as lakes, rivers, and possibly even oceans. Geological features such as valleys, channels, and basins formed during this period further support the notion of liquid water on ancient Mars. The Pre-Noachian period stands as a crucial era in Martian history, characterized by dynamic geological processes and the potential for liquid water, laying the groundwork for subsequent epochs of Martian evolution.[1][13]

References

  1. ^ a b c d e "The ages of Mars". Mars Express - European Space Agency (ESA). Retrieved 25 March 2024.
  2. doi:10.1016/j.pss.2013.05.003
    .
  3. doi:10.1016/j.epsl.2009.12.041
    .
  4. ^ Amos, Jonathan (10 September 2012). "Clays in Pacific Lavas Challenge Wet Early Mars Idea". BBC News.
  5. ^ See Mutch, T.A. (1970). Geology of the Moon: A Stratigraphic View; Princeton University Press: Princeton, NJ, 324 pp. and Wilhelms, D.E. (1987). The Geologic History of the Moon, USGS Professional Paper 1348; http://ser.sese.asu.edu/GHM/ for reviews of this topic.
  6. ^ Wilhelms, D.E. (1990). Geologic Mapping in Planetary Mapping, R. Greeley, R.M. Batson, Eds.; Cambridge University Press: Cambridge UK, p. 214.
  7. ^ Tanaka, K.L.; Scott, D.H.; Greeley, R. (1992). Global Stratigraphy in Mars, H.H. Kieffer et al., Eds.; University of Arizona Press: Tucson, AZ, pp. 345–382.
  8. ^
    doi:10.1146/annurev.earth.33.092203.122637
    .
  9. ^ International Commission on Stratigraphy. "International Stratigraphic Chart" (PDF). Retrieved 2009-09-25.
  10. ^
    ISBN 0-13-390047-9
    .
  11. ISBN 978-90-481-5725-9. {{cite book}}: |journal= ignored (help
    )
  12. ^ 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.
  13. ^
    doi:10.1002/2017JE005276
    .
  14. PMID 32332708
    . Retrieved 2024-03-26.
  15. ^ Tanaka, K.L. (2001). The Stratigraphy of Mars: What We Know, Don't Know, and Need to Do. 32nd Lunar and Planetary Science Conference, Abstract #1695. http://www.lpi.usra.edu/meetings/lpsc2001/pdf/1695.pdf.
  16. ^ Carr, 2006, p. 41.
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