Reading the climate record of the martian polar layered deposits

Hvidberg, Christine S.; Fishbaugh, K. E.; Winstrup, Mai; Svensson, Anders; Byrne, Shane; Herkenhoff, K. E.

doi:10.1016/j.icarus.2012.08.009

Cited by 76 publications

(132 citation statements)

References 35 publications

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“…As discussed in section , previous work found that reflector‐causing layers are formed through two main processes, both of which are primarily controlled by the planet's orbital parameters: the concentration of dust through ice sublimation (Levrard et al, ; Toon et al, ) or the nonuniform variation of ice and dust deposition with time (e.g., Cutts & Lewis, ; Hvidberg et al, ; Phillips et al, ; Putzig et al, ). Each process produces distinct populations of layers.…”

Section: Resultsmentioning

confidence: 99%

“…Each process produces distinct populations of layers. Lag deposits consist almost entirely of dust and either empty or ice‐filled pore space, while constructional ice layers may have much lower fractional dust contents, between 3% and 10% according to a recent model of obliquity‐driven polar ice and dust deposition (Hvidberg et al, ). However, our dust content estimates do not recreate this bimodal behavior.…”

Section: Resultsmentioning

confidence: 99%

“…Hvidberg et al () modeled NPLD accumulation using ice and dust deposition rates forced by a temperature gradient between the poles and the equator. This, in turn, was driven by the planetary obliquity cycle.…”

Section: Introductionmentioning

confidence: 99%

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Radar Reflectivity as a Proxy for the Dust Content of Individual Layers in the Martian North Polar Layered Deposits

Lalich

Holt

2019

JGR Planets

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The stratigraphy of the north polar layered deposits (NPLD) of Mars is believed to contain a climate record of the recent Amazonian period. However, full utilization of this record is difficult without detailed information regarding the physical properties of the constituent layers. Here we present a method for determining the fractional dust content of individual layers using a combination of orbital radar reflectivity measurements and physical modeling. We apply this method to the upper 500 m of the NPLD at 10 study sites and compare the results to a cap‐wide radar‐mapped surface. Our results show that reflectivity can vary drastically both geographically and with depth, a result we attribute to changing dust content, though the impact of variable layer thickness cannot be totally discounted. These findings imply large‐scale regional patterns in ice and dust accumulation do not remain consistent through time. We also find that current models of Mars's dust cycle and polar ice accumulation consistently underpredict the dust content of layers, indicating that our understanding of dust transport, dust sequestration, or dust preservation remains incomplete. Comparisons of study sites on the NPLD also show that some locations contain fewer radar reflectors than others, meaning they may contain a less complete record of the planet's recent paleoclimate, and any future efforts to use the polar layered deposits as a climate proxy, including in situ measurements, should take this into account by choosing study sites wisely.

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Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

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Radar Reflectivity as a Proxy for the Dust Content of Individual Layers in the Martian North Polar Layered Deposits

Lalich

Holt

2019

JGR Planets

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“…The PLDs are thought to have formed over the recent geologic past (10 6 –10 8 years; Byrne, ; Greve et al, ; Herkenhoff & Plaut, ; Hvidberg et al, ; Levrard et al, ; Phillips et al, ; Smith et al, ), where climate change is driven by changes in orbital elements (Laskar et al, ). Due to the abundance of troughs that expose sequences of the layered deposits, the NPLD have been the primary focus for determining a climatological record.…”

Section: Introductionmentioning

confidence: 99%

“…Due to the abundance of troughs that expose sequences of the layered deposits, the NPLD have been the primary focus for determining a climatological record. Previous studies have explored linking stratigraphic sequences to changes in Martian orbital elements (Becerra et al, ; Hvidberg et al, ; Laskar et al, ; Milkovich & Head, ; Sori et al, ). However, inferring past climate from layer properties (e.g., reflectance and protrusion) remains uncertain.…”

Section: Introductionmentioning

confidence: 99%

Thermophysical Properties of the North Polar Residual Cap using Mars Global Surveyor Thermal Emission Spectrometer

2019

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Using derived temperatures from thermal‐infrared instruments aboard orbiting spacecraft, we constrain the thermophysical properties, in the upper few meters, of the north polar residual cap of Mars. In line with previous authors we test a homogeneous thermal model (i.e., depth‐independent thermal properties), simulating water ice of varying porosity against observed temperatures. We find that high thermal inertia (>1,000 J m−2 K−1 s 1/2 or <40% porosity) provides the best fit for most of the residual cap. Additionally, we test the observed data against models with depth‐dependent thermal properties. Models tested converge on similar solutions: we find extensive regions of low surface thermal inertia consistent with a porous layer at the surface (>40% porosity) that densifies with depth into a zero‐porosity ice layer at shallow depths (<0.5 m). We interpret this as evidence of recent water ice accumulation. Our results along the edge of the residual cap imply that denser (<40% porosity) ice is present at the surface and coincides with lower albedo. These results suggest that older ice is undergoing exhumation along much of the residual cap margin. The results support recent water ice accumulation having occurred over specific regions, while ablation dominates in others.

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Spiral trough diversity on the north pole of Mars, as seen by Shallow Radar (SHARAD)

Holt

2015

JGR Planets

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We combine observations from ground penetrating radar and optical instruments to conduct a comprehensive survey of spiral troughs on the north polar layered deposits of Mars. Our survey reveals that all north polar troughs have common characteristics, but there is strong regional diversity. We divide the north polar layered deposits (NPLD) into eight regions based on observations of morphology and stratigraphy in order to classify the spiral troughs. Morphologic features that separate the regions include central promontories, topographic undulations, bedrock floors, and trough asymmetry among others. We demonstrate here that the troughs formed during two periods. The first generation of troughs formed on the main lobe and in part of Gemina Lingula during accumulation of~600 m of ice and dust. The second generation of troughs formed stratigraphically higher and immediately after large-scale erosion in Gemini Scopuli, which we conclude created the slopes necessary for troughs to form. We test scenarios of trough evolution and find that only three concurrent processes are required for their formation: wind transport, insolation-induced sublimation, and atmospheric deposition. Our observations are inconsistent with other hypothesized processes to produce spiral troughs, including incision after the formation of the NPLD, fracturing due to flowing ice, and sublimation-driven patterns from insolation.

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Reading the climate record of the martian polar layered deposits

Cited by 76 publications

References 35 publications

Radar Reflectivity as a Proxy for the Dust Content of Individual Layers in the Martian North Polar Layered Deposits

Radar Reflectivity as a Proxy for the Dust Content of Individual Layers in the Martian North Polar Layered Deposits

Thermophysical Properties of the North Polar Residual Cap using Mars Global Surveyor Thermal Emission Spectrometer

Spiral trough diversity on the north pole of Mars, as seen by Shallow Radar (SHARAD)

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