Mantled and exhumed terrains in Terra Meridiani, Mars

Abstract

[1] Hematite-bearing deposits in the Terra Meridiani region of Mars constitute the top stratum of a partially eroded layered complex that covers dissected Noachian-aged cratered terrain. The hematite unit consists of dark plains and dunes covering a bright substrate. This substrate is fully exposed beyond the borders of the hematite-bearing deposit and consists of polygonal ground separated by ridges or valleys, together with layered deposits that have been eroded into a variety of landforms. The complex is partially covered by a regional-scale aeolian mantle that thickens toward the north. The hematite-bearing stratum exhibits low albedoes, pulse widths, and intermediate thermal inertias, whereas the underlying unit exhibits high values of these parameters. Both units have spectral emissivity signatures similar to those for the low albedo cratered terrain to the south, with the addition of hematite for the top stratum. The complex is interpreted to consist of extensive plains-forming lava flows and tephra deposits emplaced during an extensional regime and at least partially buried by an aeolian mantle. Aeolian stripping of the mantle exposed much of the complex and differentially eroded the deposits to produce the landforms existent today. Exploration of the hematite-bearing deposits by the 2003 Mars Exploration Rover, ''Opportunity,'' will allow testing of the hypotheses presented since this stratum has been locally reworked into dunes that only partially cover the underlying brighter portion of the complex. In particular, the rover-based measurements will allow us to test the extent to which the unusual remote-sensing properties of the units indicate aqueous alteration.

Quantitative compositional analysis of martian mafic regions using the MEx/OMEGA reflectance data 1. Methodology, uncertainties and examples of application

“…The DCT unit falls within the globally defined low albedo, intermediate to high thermal inertia regions with exposed sands (Arvidson et al, 2003). The inferred grain sizes in the medium to fine sand size range is consistent with the thermal inertia (200 to 400 J m -2 K -1 s -1/2 ) and albedo values derived for these dark regions typically composed of coarse-grained (100-500 µm) particles (Palluconi and Kieffer, 1981;Edgett and Christensen, 1991).…”

“…In this paper, we evaluate the performance of the modeling of OMEGA maficrich spectra under a variety of conditions and attempt to provide uncertainties on the inferred modal mineralogy and grain size. An application to the Late Noachian dissected cratered terrains (DCT) in Terra Meridiani (Arvidson et al, 2003) is presented. This region provides an excellent case for the analysis of mafic surface composition because 1) it has a low albedo, and is therefore presumably relatively free of surface dust coatings, 2) analysis of previous NIR spectral data indicates that these dark regions have strong absorption features of mafic minerals throughout the OMEGA spectral range (Gendrin et al, 2006;Poulet et al, 2008), 3) although located outside the hematite unit of Meridiani Planum, this unit is sufficiently close to the MER-B landing site which provides the opportunity to better understand the atmospheric conditions of the OMEGA observations, and 4) a comparison with TES regional modal mineralogy is possible (Rogers and Christensen, 2007).…”

“…Detailed mapping of the Terra Meridiani region shows that different geological units are actually stratigraphically present. Hematite-bearing plains (Ph unit) are at the top of a section of layered material (referred as etched terrains E unit) that is hundreds of meters thick and extends beneath the Opportunity landing site; these etched terrain materials sit unconformably on the late Noachian dissected cratered terrain materials (Hynek et al, 2002;Arvidson et al, 2003;Edgett, 2005). OMEGA data covering the etched terrains show enhanced water bands at 1.9 and 3.0 µm (Jouglet et al, 2007;Poulet et al, 2008) and, in some where discrete stratigraphic horizons are exposed Griffes et al, 2007).…”

“…We use the spectral model on OMEGA reflectance spectra extracted from a part of the mafic-rich regions observed in Terra Meridiani, also referred as DCT unit (Arvidson et al, 2003). Detailed mapping of the Terra Meridiani region shows that different geological units are actually stratigraphically present.…”

Sulfate-Rich Eolian and Wet Interdune Deposits, Erebus Crater, Meridiani Planum, Mars

“…The oldest rocks constitute a Noachian-age basal unit that has been extensively dissected by channel systems (Arvidson et al 2003). Lying disconformably on top of the dissected cratered terrain is a widespread, partially eroded, layered complex consisting of several light-toned stratigraphic units.…”