Virtual Mars Globes

Medusae Fossae Formation

Medusae Fossae Formation

Origin of name:
Medusa: The Gorgon beheaded by Perseus
A név eredete:
Medusa, a gorgó, akit Perzeusz megölt és fejét elvitte ajándékba. A csillagos égen a Perzeusz csillagképben az Algol csillag jelképezi. 

Geologic description and interpretation:
The Medusae Fossae deposits are interpreted as pyroclastic ash that is widespread over the planet and accumulated at the dichotomy boundary,[1] stretching from just south of Olympus Mons to Aeolis Planum[2]The Medusae Fossae is characterized by wind-sculpted landforms, most notably eroded ridges known as yardangs. The composition of the Medusae Fossae (=Medusae Fossae Formation/unit) is not known, but candidates include indurated (hardened) volcanic ash or remnants of  that formed in a different Martian climate[3] Any such materials, irrespective of their origin, may simply accumulate at the surface and become redistributed by the wind as wind regimes change[4].

The origins of the MFF are still controversial, but the three primary hypotheses are: ash flow, ash fall, and aeolianite (i.e., loess).[1]

Aeolis Planum is composed of semi-resistant materials which have been eroded into linear ridges called yardangs[2]. Stretching from just south of Olympus Mons to Aeolis Planum (Aeolis Planum, Zephyria Planum, Lucus Planum, Eumenides Dorsum, Amazonis Mensa, Gordii Dorsum) is a region called [or: covered b/composed of] the Medusa Fossae Formation. Its materials are completely sculpted by the wind.[3] Medusae Fossae unit forms vast, discontinuous deposit along south border of Elysium and Amazonis Planitiae. Reaches hundreds of meters in thickness. Appears to be made up of sequence of layers Interpretation:  volcanic ash deposits from local, buried vents and (or) other uncertain origin(s). Ridges and grooves in most cases appear to be wind-eroded landforms controlled by structural fabric and (or) wind patterns[4].

Geológiai leírás és magyarázat:
A Medusae Fossae Formáció üledékeinak anyaga piroklasztit (vulkáni) hamu. Az egész bolygón tovaterjedtek és az É-D dichotómia határon halmozódtak föl. Anyagukat később a szél formálta maradékgerincekké. Egy másik elmélet szerint anyaguk lösz. Lásd még: Aeolis Planum

[1] Bradley, B. A., S. E. H. Sakimoto, H. Frey, and J. R. Zimbelman (2002), Medusae Fossae Formation: New perspectives from Mars Global Surveyor, J. Geophys. Res., 107(E8), 5058, doi:10.1029/2001JE001537.

[2] NASA Planetary Photojournal captiion online: PIA10884: Yardangs

[3] THEMIS website 2007: online caption: THEMIS Image of the Day: Wind Etching

[4] Kenneth L. Tanaka, James A. Skinner, Jr., and Trent M. Hare Geologic Map of the Northern Plains of Mars Scientific Investigations Map 2888 USGS 2005 NPlains_geology_SIM2888_2005_pamphlet.pdf

[1] Wernera, Stephanie C. 2008: The global martian volcanic evolutionary history Icarus Article in Press

[2] THEMIS Image of the Day: Wind Etching. Online caption on THEMIS website.

[3] H IRISE 2006: Yardangs in the Medusae Fossae Formation.  HIRISE caption online.

[4] Carr, Michael H.: 2006 The Surface of Mars (Cambridge Univ. Press), Cambridge planetary science No. 5.