Nirgal Vallis

Nirgal Vallis
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Nirgal Vallis based on THEMIS day-time image
Coordinates28°24′S 42°00′W / 28.4°S 42°W / -28.4; -42
Namingthe word for "Mars" in Babylonian

Nirgal Vallis is a long river channel bordering the Coprates quadrangle and Margaritifer Sinus quadrangle of Mars at 28.4° south latitude and 42° west longitude. It is 610 km long and is named after Nergal, the Babylonian god of war and counterpart to the Roman god of war Mars.[1] Nirgal Vallis had a discharge of 4800 cubic meters/second.[2] The western half of Nirgal Valles is a branched system, but the eastern half is a tightly sinuous, deeply entrenched valley. Nirgal Valles ends at Uzboi Vallis. Tributaries are very short and end in steep-walled valley heads, often called "amphitheater-headed valleys." The shape of these valley heads is like cirques on the Earth.[3]

Water from Nirgal Vallis contributed to a great flood that went through the rim of Holden Crater and helped form a lake in the crater. It's estimated that Nirgal Vallis had a discharge of 4800 cubic meters/second.[4] Water from Nirgal Vallis was inbounded in Uzboi Vallis because the rim of Holden Crater blocked the flow. At a certain point the stored water broke through the rim of Holden and created a lake 200–250 m deep.[5] Water with a depth of at least 50 m entered Holden at a rate that 5-10 times the discharge of the Mississippi River.[6][7][8][9] Terraces and the presence of large rocks (tens of meters across) support these high discharge rates.[5][6][10][11][12]

  • Map showing locations Nirgal Vallis and other nearby valleys
    Map showing locations Nirgal Vallis and other nearby valleys
  • Viking Orbiter 1 image showing the entire valley
    Viking Orbiter 1 image showing the entire valley
  1. ^ "Nirgal Vallis". Gazetteer of Planetary Nomenclature. USGS Astrogeology Research Program.
  2. ^ Irwin, J., R. Craddock, R. Howard. 2005. Interior channels in Martian valley networks: Discharge and runoff production. Geology: 33,489-492.
  3. ^ Baker, V. 1982. The Channels of Mars. University of Texas Press. Austin
  4. ^ Irwin, J., R. Craddock, R. Howard. 2005. Interior channels in Martian valley networks: Discharge and runoff production. Geology: 33,489-492.
  5. ^ a b Grant, J., R. Irwin, S. Wilson. 2010. Aqueous depositional settings in Holden crater, Mars In Cabrol, N. and E. Grin (eds.). 2010. Lakes on Mars. Elsevier. NY.
  6. ^ a b Grant, J., T. Parker. 2002. Drainage evolution of the Margaritifer Sinus region, Mars. J. Geophysic. Res. 107, doi:10.1029/2001JE001678.
  7. ^ Komar, P. 1979. Comparisons of the hydraulics of water flows in Martian outflow channels with flows of similar scale on Earth. Icarus: 37, 156-181.
  8. ^ Grant, J. et al. 2008. HiRISE imaging of impact megabreccia and sub-meter aqueous strata in Holden Crater, Mars. Geology: 36, 195-198.
  9. ^ Irwin, et al. 2005. An intense terminal epoch of widespread fluvial activity on early Mars: 2. Increased runoff and paleolake development. J. Geophysical. Res. 110, E12S14, doi: 10.1029/2005JE002460.
  10. ^ Boothroyd, J. 1983. Fluvial drainage systems in the Ladon Basin area: Margaritifer Sinus area, Mars. Geol. Soc. Am. Abstr. Programs 15, 530
  11. ^ Grant, J. 1987. The geomorphic evolution of Eastern Margaritifer Sinus, Mars. Adv. Planet. Geol. NASA Tech memo. 89871, 1-268.
  12. ^ Parker, T. 1985. Geomorphology and geology of the southwestern Margaritifer Sinus-northern Argyre region of Mars, California State University, M. S. Thesis, Los Angeles, California