Encyclopedia of Astrobiology

Living Edition
| Editors: Muriel Gargaud, William M. Irvine, Ricardo Amils, Henderson James Cleaves, Daniele Pinti, José Cernicharo Quintanilla, Michel Viso

Outflow Channels

  • Ernst HauberEmail author
Living reference work entry
DOI: https://doi.org/10.1007/978-3-642-27833-4_1133-3


Erosion Flooding Groundwater Ice Water 


Outflow channels on Mars are large channel systems that emerge fully-sized from rubble-filled “chaotic” depressions, are generally tens of kilometers across and hundreds of kilometers long, and were formed by fluid flow of water from subsurface reservoirs.


Outflow channels were first detected on images from the Mariner 9 mission (Baker and Milton 1974). They are the strongest morphological evidence that large amounts of water once flowed on the Martian surface. Characteristic landforms of outflow channels are anastomosing (building a network of streams that both branch out and reconnect) channels, streamlined erosional “islands,” dry cataracts, and scour marks and grooves on the channel floors (Baker 1982). The closest terrestrial analog for outflow channels is the huge complex of anastomosing rock-cut fluvial channels in east-central Washington (USA). This so-called Channeled Scabland was first interpreted by J Harlan Bretz as the result of the catastrophic megaflooding derived from ice-dammed Pleistocene glacial lakes (e.g., Bretz 1923), an interpretation which challenged the conventional geologic wisdom of Uniformitarianism and was, therefore, heavily debated (Baker 2009). Uniformitarianism (as described by Bates and Jackson 1980) is the fundamental principle or doctrine that geologic processes and natural laws now operating to modify the Earth’s crust have acted in the same regular manner and with essentially the same intensity throughout geologic time, and that past geologic events can be explained by phenomena and forces observable today; the classical concept that “the present is the key to the past.” Many models of the formation of Martian outflow channels favor a catastrophic formation by the sudden release of large amounts of water from subsurface reservoirs. Pressurized aquifers might have existed below an impermeable frozen upper crust (the cryosphere), which was then cracked by the ascent of volcanic dikes (e.g., Head et al. 2003). Alternatively, outflow channels might have been eroded, at least partly, by glacial processes (Lucchitta 1982). Most, if not all, outflow channels show evidence for a multistage formation with different phases of activity separated by geologically long periods of time. Outflow channel activity spans a long time, from ≫3.5 Ga to geologically very recent times (Neukum et al. 2010). Outflow channels terminate into the northern lowlands of Mars and might have fed an ancient northern ocean (Baker et al. 1991), although this scenario is contentious.

See Also

References and Further Reading

  1. Baker VR (1982) The channels of Mars. University of Texas Press, Austin, 198 ppGoogle Scholar
  2. Baker VR (2009) The Channeled Scabland: a retrospective. Annu Rev Earth Planet Sci 37:393–411ADSCrossRefGoogle Scholar
  3. Baker VR, Milton DJ (1974) Erosion by catastrophic floods on Mars and Earth. Icarus 23:27–41ADSCrossRefGoogle Scholar
  4. Baker VR, Strom RG, Gulick VC, Kargel JS, Komatsu G, Kale VS (1991) Ancient oceans, ice sheets and the hydrological cycle on Mars. Nature 352:589–594ADSCrossRefGoogle Scholar
  5. Bates R, Jackson J (1980) Glossary of geology, 2nd edn. American Geological Institute, Falls Church, Virginia, 677 ppGoogle Scholar
  6. Bretz H (1923) The Channeled Scabland of the Columbia Plateau. J Geol 31:617–649ADSCrossRefGoogle Scholar
  7. Head JW, Wilson L, Mitchell KL (2003) Generation of recent massive water floods at Cerberus Fossae, Mars by dike emplacement, cryospheric cracking, and confined aquifer groundwater release. Geophys Res Lett 30:1577. doi:10.1029/2003GL017135ADSCrossRefGoogle Scholar
  8. Lucchitta BK (1982) Ice sculpture in the Martian outflow channels. J Geophys Res 87:9951–9973ADSCrossRefGoogle Scholar
  9. Neukum G, Basilevsky AT, Kneissl T, Chapman MG, Van Gasselt S, Michael G, Jaumann R, Hoffmann H, Lanz JK (2010) The geologic evolution of Mars: episodicity of resurfacing events and ages from cratering analysis of image data and correlation with radiometric ages of Martian meteorites. Earth Planet Sci Lett 294:204–222ADSCrossRefGoogle Scholar

Copyright information

© Springer-Verlag Berlin Heidelberg 2014

Authors and Affiliations

  1. 1.Deutsches Zentrum für Luft- und Raumfahrt (DLR) e.V.Institut für PlanetenforschungBerlinGermany