Mineralogy of Juventae Chasma: sulfates in the light-toned mounds, mafic minerals in the bedrock, and hydrated silica and hydroxylated ferric sulfate on the plateau

Bishop, Janice L.
Parente, M.
Weitz, C. M.
Noe Dobrea, E. Z.
Roach, L. H.
Murchie, S. L.
McGuire, P. C.
McKeown, Nancy
Rossi, C. M.
Brown, A. J.
Faculty Advisor
Mars , spectroscopy , sulfate , Juventae Chasma , layered deposits
Abstract (summary)
Juventae Chasma contains four light-toned sulfate-bearing mounds (denoted here as A-D from west to east) inside the trough, mafic outcrops at the base of the mounds and in the wall rock, and light-toned layered deposits of opal and ferric sulfates on the plateau. Hyperspectral visible/near-infrared Compact Reconnaissance Imaging Spectrometer for Mars (CRISM) spectra were used to identify monohydrated and polyhydrated sulfate (PHS) outcrops of layered material on the bright mounds. Most of the monohydrated sulfate signatures closely resemble those of szomolnokite (FeSO (sub 4) H (sub 2) O), characterized by a water band near 2.08 mu m, while some areas exhibit spectral features more similar to those of kieserite (MgSO (sub 4) H (sub 2) O), with a band centered closer to 2.13 mu m. The largest PHS outcrops occur on the top of mound B, and their spectral features are most consistent with ferricopiapite, melanterite, and starkeyite, but a specific mineral cannot be uniquely identified at this time. Coordinated analyses of CRISM maps, Mars Orbiter Laser Altimeter elevations, and High Resolution Imaging Science Experiment images suggest that mounds A and B may have formed together and then eroded into separate mounds, while mounds C and D likely formed separately. Mafic minerals (low-Ca pyroxene, high-Ca pyroxene, and olivine) are observed in large approximately 2-10 km wide outcrops in the wall rock and in smaller outcrops approximately 50-500 m across at the floor of the canyon. Most of the wall rock is covered by at least a thin layer of dust and does not exhibit strong features characteristic of these minerals. The plateau region northwest of Juventae Chasma is characterized by an abundance of light-toned layered deposits. One region contains two spectrally unique phases exhibiting a highly stratified, terraced pattern. CRISM spectra of one unit eroded into swirling patterns with arc-like ridges exhibit a narrow 2.23-mu m band assigned to hydroxylated ferric sulfate. A thin layer of a fractured material bearing an opaline silica phase is observed at the contact between the older plateau unit and the younger hydroxylated ferric sulfate-bearing light-toned layered deposits. Hydrothermal processes may have produced an acidic environment that fostered formation of the hydrated silica and hydroxylated ferric sulfate units.
Publication Information
Bishop, J. L., Weitz, C., Noe Dobrea, E. Z., Roach, L. H., Murchie, S. L., McGuire, P., McKeown, N. K., Rossi, C., Brown, A. J., Calvin, W., Milliken, R. E., & Mustard, J. F. (2009). Mineralogy of Juventae Chasma: sulfates in the light-toned mounds, mafic minerals in the bedrock, and hydrated silica and hydroxylated ferric sulfate on the plateau, Journal of Geophysical Research- Planets, 114(E2), E00D09, doi: 10.1029/2009JE003352.
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