Low thermal inertia regions on Mars, such as Tharsis Montes, Arabia Terra, and Elysium Planitia cover about a third of the Martian surface and the majority of the northern midlatitudes and are interpreted to be surfaces mantled in dust [e.g., Kieffer et al., 1973, 1977; Palluconi and Kieffer, 1981]. Eastern Arabia Terra (referred to as Arabia Terra in this work) contains morphologic features that can be viewed through this dust mantle, such as layers exposed within craters [e.g., Malin and Edgett, 2001; Edgett and Malin, 2002], dark intracrater material [e.g., Arvidson, 1974; Christensen, 1983; Thomas, 1984; Edgett and Malin, 2000; Edgett, 2002; Wyatt et al., 2003], and evidence for fluvial and volcanic processes [e.g., Zimbelman and Greeley, 1982; Greeley and Guest, 1987; Anguita et al., 1997]. The relationship between the processes that produced these features and those that formed the dust mantle offers insight into geologic environments and climates on Mars.
 Arabia Terra (Figure 1) is an ideal location to study the current and historical transport and deposition of dust because there are no major topographic structures, such as the Tharsis or Elysium Montes, that influence local wind circulation patterns, and this region has likely been a region with atmospheric conditions favorable for dust accumulation throughout much of Martian history [e.g., Haberle et al., 2003; Kahre et al., 2006; Haberle et al., 2006]. The objectives of this work are to (1) better understand the current sedimentary processes of dust accumulation and sand transport and its relationship to past sedimentary processes of deposition and erosion; and (2) expand these ideas to gain new insight into the cycles of dust circulation and deposition on Mars and relate this information to understanding past climates. These objectives have been addressed using multiple data sets to create a unit map of eastern Arabia Terra, Mars. This map is then used to facilitate the interpretation of the geologic history of this region, focusing on the present and past dust cycle and the formation of layered materials.
1.1. Transport and Properties of Martian Dust
 Dust is believed to be primarily transported and deposited during and just after major dust events [e.g., Kahn et al., 1992]. In the present climate, planet-encircling dust events typically originate in the southern hemisphere in the regions of Hellespontus west of Hellas basin or Solis Planum [e.g., Briggs et al., 1979; Zurek, 1982; Martin, 1984; Strausberg et al., 2005]. After a planet-encircling dust event, dust settles out of the atmosphere uniformly over the planet. Areas of high wind shear stress are observed to have an increased atmospheric opacity, indicating the presence of airborne dust [Christensen, 1982], and experience post dust event darkening [e.g., Sagan and Pollack, 1969; Pleskot and Miner, 1981; Christensen, 1988]. These typically low-albedo surfaces become a local dust source as dust is removed from these regions and is redeposited on adjacent areas of low wind shear stress [Christensen, 1982]. Dust is also observed locally, and has been observed at all of the Martian landing sites [e.g., Moore et al., 1977, 1999; Greeley et al., 1999; Soderblom et al., 2004; Herkenhoff et al., 2004; Christensen et al., 2004b]. Thus, dust likely covers much of the planet but in thinner, more patchy deposits than the low thermal inertia regions. The thermal infrared spectral signature of dust is similar for all moderate to high-albedo regions [e.g., Bandfield and Smith, 2003], and the spectral and chemical signature of the dust component is similar at each landing site [e.g., McSween and Keil, 2000; Christensen et al., 2004b, 2004c, Yen et al., 2005]. Both observations indicate that bright air fall dust is not derived from local material, but instead suggests a global mixing mechanism for surface dust [e.g., McSween and Keil, 2000; Ruff and Christensen, 2002; Yen et al., 2005].
 The effective radius of atmospheric dust is ∼1.5 μm [Toon et al., 1977; Pollack et al., 1979; Clancy et al., 2003; Wolff and Clancy, 2003; Wolff et al., 2006]. This is lower than the 20–40-μm diameter implied by the thermal inertia data in regions inferred to be mantled in dust [Christensen, 1986a; Mellon et al., 2000; Putzig et al., 2005]. Jakosky  suggests that gas conductivity may not vary significantly between particle diameters of 3 and 40 μm, and therefore the thermal inertia of 3- and 40-μm diameter particles may not be appreciably different [Christensen, 1986a]. Presley and Christensen  measured the conductivity for 0–11 μm, 11–15.6 μm, 15.6–20 μm, and 25–30 μm size fractions. Although the 15.6–20 μm and 25–30 μm diameter particles have a similar conductivity, all other size fractions differ in conductivity under Martian atmospheric conditions. This laboratory result suggests that some additional process has occurred to increase the particle size of the surface dust mantle relative to atmospheric dust. This dust material could be a pyroclastic ashfall deposit in which air-filled vesicles lower the thermal inertia significantly [e.g., Kieffer et al., 1973; Zimbelman, 1986]. However, this material has a uniform thermal inertia and albedo, whereas a pyroclastic ash would likely have more variable thermophysical characteristics because of variations in erosion of the ash material [Zimbelman, 1986]. Thus, an unconsolidated air fall dust interpretation is a more likely explanation for the low thermal inertia deposits. The low thermal inertia regions may be composed of larger particle sizes than that of atmospheric dust, or more likely, some later process, such as electrostatic forces [e.g., White et al., 1997] or cementation [e.g., Jakosky and Christensen, 1986; Arvidson et al., 2006], may be causing smaller sized air fall dust particles to bond together.
1.2. Geologic Setting
 The study region in Arabia Terra is located from 20.0°E to 32.5°E longitude and 6.5°S to 13.5°N latitude and using primarily Viking data was mapped into dissected (Npld), ridged (Nplr), subdued cratered (Npl2), and ridged plains material (Hr) units [Greeley and Guest, 1987]. This region was mapped using visible images and although a dust mantle was known to be present, this dust layer was not considered and features observed through the dust mantle were mapped. The majority of this area is dissected unit material (Npld) interpreted to have formed during heavy bombardment during the Noachian Period. This surface is likely a mixture of volcanic materials, erosional products, and impact breccia, and is highly dissected by channels and channel networks. Ridged unit material (Nplr) is found in the western portion of the study area, is interpreted to be flood lava flows and ridges likely due to volcanic processes, and is also Noachian in age. In Henry crater subdued crater unit material (Npl2) fills the crater floor, and is interpreted to be either thin lava flows or sedimentary deposits [Greeley and Guest, 1987]; this is the only mapped occurrence of this material in the study region. In addition, there is a small region of ridged plains material (Hr) in the southern portion of the study area that is interpreted to be low-viscosity lava flows and Hesperian in age. Some craters contain smoother material filling the floors and occasionally central peaks, crater-rim, and crater-ejecta material are present [Greeley and Guest, 1987].
 Arabia Terra has a Thermal Emission Spectrometer (TES) [Christensen et al., 1992, 2001] bolometric albedo of 0.25 to 0.30, a TES-derived thermal inertia of 40–120 J m−2 K−1 s−1/2, and is interpreted to be a surface dominated by unconsolidated fines less than about 40 μm in diameter [e.g., Palluconi and Kieffer, 1981; Mellon et al., 2000; Putzig et al., 2005]. The regional rock abundance from Viking data is 5–7% [Christensen, 1982, 1986b; Zimbelman and Greeley, 1982] and less than ∼7% from TES data [Nowicki and Christensen, 2007], and is among the lowest observed on the planet. On the basis of Viking data, Arabia Terra is interpreted to be mantled in a dust layer a few centimeters to 1–2 m thick; the thickness is constrained by the low thermal inertia and morphologic features that can still be discriminated [Christensen, 1986a]. The dust layer has been interpreted to be less than ∼105 years old, on the basis of estimates of average annual dust deposition from planet-encircling dust events (10 μm/a, where a is years) and assuming a dust mantle thickness of 1 m [Christensen, 1986a]. Also, Bandfield and Edwards  infer that Arabia Terra, Elysium Planitia, and Tharsis Montes are extraordinarily smooth surfaces at centimeter to meter scales, consistent with fine material mantling the surface.
 The study region has the highest concentrations of hydrogen outside the polar regions, as identified by the Mars Odyssey Gamma Ray Spectrometer/Neutron Spectrometer/High-Energy Neutron Detector (GRS/NS/HEND) instrument suite [e.g., Boynton et al., 2002; Feldman et al., 2002; Mitrofanov et al., 2002, Feldman et al., 2004; Mitrofanov et al., 2004; Ivanov et al., 2005; Jakosky et al., 2005], and is interpreted as having up to ∼10% water content in the uppermost surface layer [Feldman et al., 2004; Mitrofanov et al., 2004; Ivanov et al., 2005; Jakosky et al., 2005]. Because of a rough correlation with low-albedo terrains, including Arabia Terra, some hypotheses suggest that the enrichment in hydrogen is related to the surface dust mantle, likely in either adsorbed water from the atmosphere or a chemically bound form [e.g., Mitrofanov et al., 2004; Ivanov et al., 2005], with water-bearing minerals being the preferred explanation [Ivanov et al., 2005]. However, there is not a strong correlation between the low thermal inertia surfaces and the hydrogen elemental abundance, particularly on local scales and in the Tharsis region [Jakosky et al., 2005], and therefore atmospheric phenomenon may be playing a role [Jakosky et al., 2005].
 This dust layer masks the underlying surface from remote sensing observations, preventing the identification of the surface composition or the thermal inertia of this material. However, morphologic features, such as wrinkle ridges, channels, and bed forms, can be identified through this mantle [e.g., Zimbelman and Greeley, 1982; Anguita et al., 1997; Malin and Edgett, 2001]. In addition, craters containing dark albedo material in their floors, similar to intracrater deposits observed in Oxia Palus to the west [e.g., Arvidson, 1974; Christensen, 1983; Thomas, 1984; Presley and Arvidson, 1988; Edgett and Christensen, 1994; Edgett, 2002; Edgett and Malin, 2002; Wyatt et al., 2003] are common, and the Mars Orbiter Camera (MOC) [Malin et al., 1992] and High Resolution Imaging Science Experiment (HiRISE) [McEwen et al., 2007] have imaged intracrater materials, including sand dunes, sand sheets, layered materials, and mesa-forming units [Malin and Edgett, 2000; Edgett and Malin, 2000; Malin and Edgett, 2001].