The NASA picture shown here is a composite of 9 color strips taken by the Mars Global Surveyor Mars Orbiter Camera (MOC) on 9 successive orbits from pole-to-pole over the planet during the calibration phase of the mission in March 1999. The large, circular bright region that dominates the scene is Arabia Terra. Syrtis Major is the dark region toward the lower right. The north polar cap is visible at the top, and the bright feature at the lower right is the Hellas Basin. The color in this picture is computer-enhanced and is not shown as it would actually appear to the human eye.
Arabia Terra is a large region of cratered terrane extending from about 20° W. longitude eastward across the prime meridian to about 300° W. longitude for an average east-west width of about 5,000 km. The northern boundary ranges from 40° N. to 45° N.; the southern boundary is a poorly defined zone at about 0° N. Thus, the north-south width is about 2,500 km. Except for the westernmost part, Arabia Terra has an albedo higher than surrounding terranes. The four quadrangles mapped (30332, 35332, 40332, 45332) provide a north-south strip from highland terrane in the south to lowland terrane in the north.
The northern portion of Arabia Terra is the type region for both fretted terrane and fretted valleys (Sharp, 1973; Sharp and Malin, 1975) and, along with the immediately adjacent northern plains, is also the site of some of the best examples of putative flow deposits present as aprons around isolated knobs and mesas or as deposits on the floors of fretted valleys and on the lowland surface (Squyres, 1978, 1979). Mass wasting, eolian erosion or deposition, glacial scouring, fluvial or shoreline erosion, deposition from an ocean, hydrovolcanism, plateau volcanism, and faulting have all been proposed to account for the topography and crater characteristics in northern Arabia Terra (Sharp, 1973; Lucchitta, 1978; Greeley and Guest, 1987; Maxwell and McGill, 1987; Parker and others, 1989; Dimitriou, 1990; Moore, 1990; Grant and Schultz, 1990, 1993; Craddock and Maxwell, 1993; Edgett and Parker, 1997; Carruthers and McGill, 1998; Tanaka, 2000; McGill, 2000). Although underlain by what appears to be typical highland terrane, Arabia Terra is anomalously low, with elevations generally below the planetary reference (Smith and others, 1999).
Probably the most important question concerning the global-scale tectonic history of Mars is the origin of the crustal dichotomy. The northern lowland is not only several kilometers lower than the southern highland, it also is surfaced by materials that are significantly younger than surface materials in the southern highland (Scott and Tanaka, 1986; Greeley and Guest, 1987; Tanaka and Scott, 1987). The young surface materials in the lowland rest unconformably on basement material having an age comparable to the exposed ancient highland terrane to the south (Scott, 1978; Maxwell and McGill, 1987; McGill, 1989; McGill and Dimitriou, 1990; Schultz and Frey, 1990). The age of the dichotomy continues to be controversial, as does the mechanism for its formation, as reviewed by McGill and Squyres (1991). Gravity and topography data from Mars Global Surveyor, however, does appear to favor early formation due to internal processes (Zuber and others, 2000). Because complex depositional and erosional events affected the boundary since its formation, the cause and history of these events must be unraveled before we can directly attack the fundamental question of the reason for the dichotomy.
Download this map a PDF file (i2746.pdf; 149 MB)
Note: This map measures 53 x 40 inches and is best reproduced on a large-format plotter at 600 dpi or greater. The PDF provided can be viewed on screen
Download a free copy of Adobe Reader .
This report is also available in printed form by writing:
USGS Information Services
Box 25286, Federal Center
Denver, CO 80225
Telephone: 1-888-ASK-USGS
E-mail: infoservices@usgs.gov
For questions about the contents of this publication, contact Ken Tanaka
| Help
| PDF help |
| Publications main page
| Plantary maps |
| U.S. Department of the Interior
| U.S. Geological Survey |
| Geologic Division
| Astrogeology |
| Privacy statement
| Disclaimer
| Accessibility |
The URL for this page is: http://pubs.usgs.gov/imap/i2746/
Please send comments and suggestions, or report problems, to:
Michael Diggles
Created: May 2, 2003 (cad)
Updated: June 22, 2007 (bwr, mfd)