page_title: Noachis quadrangle
section_title: Scalloped topography
hierarchical_section_title: Noachis quadrangle / Scalloped topography
caption_attribution_description: English: Scalloped Terrain at Peneus Patera, as seen by hirise. Location is 57 degrees south latitude and 51.3 degrees east longitude. Image was taken by the Mars Reconnaissance Orbiter's HiRISE. The HiRISE camera was built by Ball Aerospace and Technology Corporation and is operated by the University of Arizona. Image courtesy NASA/JPL/University of Arizona.
context_page_description: The Noachis quadrangle is one of a series of 30 quadrangle maps of Mars used by the United States Geological Survey Astrogeology Research Program. The Noachis quadrangle is also referred to as MC-27.
  The Noachis quadrangle covers the area from 300° to 360° west longitude and 30° to 65° south latitude on Mars. It lies between the two giant impact basins on Mars: Argyre and Hellas. The Noachis quadrangle includes Noachis Terra and the western part of Hellas Planitia.
  Noachis is so densely covered with impact craters that it is considered among the oldest landforms on Mars—hence the term "Noachian" for one of the earliest time periods in martian history.
  In addition, many previously buried craters are now coming to the surface, where Noachis' extreme age has allowed ancient craters to be filled, and once again newly exposed.
  Much of the surface in Noachis quadrangle shows a scalloped topography where the disappearance of ground ice has left depressions.
  The first piece of human technology to land on Mars landed in the Noachis quadrangle. The Soviet's Mars 2 crashed at 44.2°S 313.2°W. It weighed about one ton. The automated craft attempted to land in a giant dust storm.
context_section_description: Certain regions of Mars display scalloped-shaped depressions. The depressions are believed to be the remains of an ice-rich mantle deposit.  Scallops are created when ice sublimates from frozen soil. This mantle material probably fell from the air as ice formed on dust when the climate was different due to changes in the tilt of the Mars pole. The scallops are typically tens of meters deep and from a few hundred to a few thousand meters across.  They can be almost circular or elongated.  Some appear to have coalesced, thereby causing a large heavily pitted terrain to form.  A study published in Icarus, found that the landforms of scalloped topography can be made by the subsurface loss of water ice by sublimation under current Martian climate conditions.  Their model predicts similar shapes when the ground has large amounts of pure ice, up to many tens of meters in depth.
  The process of producing the terrain may begin with sublimation from a crack because there are often polygon cracks where scallops form.
caption: Scalloped Terrain at Peneus Patera, as seen by HiRISE.  Scalloped terrain is quite common in some areas of Mars.
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