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Fossil Fans in Melas Chasma

Captioned Image Release No. MSSS-2 — 13 April 2007

(A) and (B) Mosaic of sub-frames of MGS MOC images R12-00541 and R17-01687
M G S MOC image mosaic showing fossil fans in sedimentary rock.
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(C) Sub-frame of MRO CTX image P05_002828_1711_XI_08S076W_070304
Subframe of a M R O C T X image showing the location of the fossil fans identified in M G S M O C images in Melas Chasma.
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full size (18.8 MB) -- full size, no annotation (18.8 MB)

NASA/JPL/Malin Space Science Systems

The geologic history of ancient Mars—and the kinds of environments that existed back then—are revealed through layered sedimentary rocks. Such rocks are created when weathering breaks down older rock, and wind and water transport the rock fragments to a location where they are deposited and subsequently lithified—turned back into rock—by cementation and compaction.

During its 9 year mission at Mars, the Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) discovered many complex relationships within martian sedimentary rocks. One of the most complicated locations it found occurs along the southern margin of Melas Chasma, one of the large troughs of the Valles Marineris system.

These images show a portion of a topographic depression eroded into layered rocks. Erosion has revealed layers of different ages—the oldest are at the bottom of the depression. Within this depression are two sets of alluvial—that is, water-lain—sedimentary rock units that retain their original shape, indicating how the sediments were deposited long before the material became rock. In these cases, the processes created fans of debris with finger-like protrusions at the ends and sides of the fans. Also preserved are the channels through which water and sediment flowed. In Figures (A) and (B), the pictures are identical except that in (A) the fans have been colored to indicate their location. Long after these fans were formed, they were buried and subsequently uncovered by more recent erosion.

Figures (A) and (B) are map-projected mosaics of MOC images R12-00541 and R17-01687. They were taken in 2003 and 2004, respectively, during the second MGS mission extension, the third Mars year that MGS was in its nearly-circular, nearly-polar mapping orbit. Figure (C) shows the context of the images in Figures (A) and (B) in the area outlined by a white box. Figure (C) is a sub-frame of Mars Reconnaissance Orbiter (MRO) Context Camera (CTX) image P05_002828_1711_XI_08S076W_070304, acquired last month on 4 March 2007. Sunlight illuminates all of these scenes from the left. The area of interest is located near 9.9°S, 76.6°W.

Citation and Credit
The image(s) and caption are value-added products. MSSS personnel processed the images and wrote the caption information. While the image(s) are in the Public Domain, NASA/JPL/MSSS requests that you credit the source of the image(s). Re-use of the caption text without credit is plagiarism. Please give the proper credit for use of the image(s) and/or caption.

Image Credit:
NASA/JPL/Malin Space Science Systems

To cite the image(s) and caption information in a paper or report:
Malin, M. C., and K. S. Edgett (2007), Fossil Fans in Melas Chasma, Malin Space Science Systems Captioned Image Release, MSSS-2,

Malin Space Science Systems (MSSS) built and operates the Mars Reconnaissance Orbiter (MRO) Mars Color Imager (MARCI) and Context Camera (CTX). MSSS also built and operated the Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC). In addition, MSSS built the Mars Odyssey (ODY) Thermal Emission Imaging Spectrometer (THEMIS) Visible (VIS) camera subsystem, which shares optics with the thermal infrared instrument and is operated at Arizona State University (ASU). MSSS built the Mars Descent Imager (MARDI) for the Phoenix Mars Scout lander and in 2007 is designing and building camera systems for the Mars Science Laboratory (MSL) rover mission, the Lunar Reconnaissance Orbiter (LRO), and the Juno mission to Jupiter.