Protonilus Mensae

Protonilus Mensae
Tributary Glacier, in Protonilus Mensae as seen by HiRISE.
Coordinates43°52′N 49°24′E / 43.86°N 49.4°E / 43.86; 49.4

Protonilus Mensae is an area of Mars in the Ismenius Lacus quadrangle. It is centered on the coordinates of 43.86° N and 49.4° E. Its western and eastern longitudes are 37° E and 59.7° E. North and south latitudes are 47.06° N and 39.87° N.[1] Protonilus Mensae is between Deuteronilus Mensae and Nilosyrtis Mensae; all lie along the Martian dichotomy boundary. Its name was adapted by the IAU in 1973.

  • Map showing the relation of Protonilus and Deuteronilus Mensae to other nearby regions. Colors refer to altitudes.
    Map showing the relation of Protonilus and Deuteronilus Mensae to other nearby regions. Colors refer to altitudes.

The surface is described as fretted terrain. This terrain contains cliffs, mesas, and wide flat valleys. Surface features are believed to have been caused by debris-covered glaciers.[2][3] These glaciers are termed lobate debris aprons (LDA) when surrounding mounds and mesas. When glaciers are in valleys, they are called Lineated valley fill (LVF). Parts of the surface show flow patterns that start in numerous alcoves located within the walls of plateaus. Small flow lobes on top of main flows demonstrate that there was more than one glacial period, just as on Earth.[4] It is strongly believed that beneath a thin layer of rock and dust lie vast reservoirs of ice.[5][6] Radar data from the SHAllow RADar (SHARAD) on board MRO have found pure ice under LDA and LVF.[7]

Some places in Protonilus Mensae display lines of pits. These pits may have formed when ground ice converted to a gas, thus leaving a void. When surface material collapses into voids, pits are created.[8]

  1. ^ http://planetarynames.wr.usgs.gov/Feature[permanent dead link]
  2. ^ Sharp, R. 1973. Mars Fretted and chaotic terrains. J. Geophys. Res.: 78. 4073-4083
  3. ^ NASA.gov
  4. ^ Baker, M. et al. 2010. Flow patterns of lobate debris aprons and lineated valley fill north of Ismeniae Fossae, Mars: Evidence for extensive mid-latitude glaciation in the Late Amazonian. Icarus: 207. 186-209.
  5. ^ Morgan, G. and J. Head III. 2009. Sinton crater, Mars: Evidence for impact into a plateau ice field and melting to produce valley networks at the Hesperian-Amazonian boundary. Icarus: 202. 39-59.
  6. ^ Morgan, G. et al. 2009. Lineated valley fill(LVF) and lobate debris aprons (LDA) in the Deuteronilus Mensae northern dichotomy boundary region, Mars: Constraints on the extent, age, and periodicity of Amazonian glacial events. Icarus: 202. 22-38.
  7. ^ Plaut, J., A. Safaeinili,, J. Holt, R. Phillips, J. Head, J., R. Seu, N. Putzig, A. Frigeri. 2009. Radar evidence for ice in lobate debris aprons in the midnorthern latitudes of Mars. Geophys. Res. Lett. 36. doi:10.1029/2008GL036379.
  8. ^ "HiRISE | Fretted Terrain Valley Traverse (PSP_009719_2230)". Hirise.lpl.arizona.edu. Retrieved December 19, 2010.