Measurements of thermal properties of icy Mars regolith analogs

Siegler, M. A.; Aharonson, O.; Carey, E. M.; Choukroun, Mathieu; Hudson, T. L.; Schörghofer, N.; Xu, S.

doi:10.1029/2011je003938

Cited by 51 publications

(22 citation statements)

References 58 publications

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“…The uncertainty in this parameter therefore contributes to less than a factor of two uncertainty in our retreat results and could lower the amounts of retreat by up to 30% or increase them by up to 50%. We calculate thermal conductivity of our icy layers (pore‐filling ice and excess ice of the NPLD) assuming a linear volumetric mixture of ice and rock (Siegler et al, ). Table summarizes the thermophysical properties used in the model.…”

Section: Methodsmentioning

confidence: 99%

A Migration Model for the Polar Spiral Troughs of Mars

et al. 2019

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Mars' iconic polar spiral troughs are 400–1,000‐m‐deep depressions in the north polar layered deposits. As the north polar layered deposits accumulate, troughs migrate approximately poleward, anti‐parallel to the local wind patterns. Insolation is suspected to drive ice retreat through sublimation. Sublimation at the trough wall produces a growing sublimation lag that modulates further retreat; however, winds move material off the retreating slope faces, thinning the lag. Discontinuities in stratigraphy seen by radar highlight Trough Migration Paths (TMPs), which provide a record of the troughs' position, formation, and evolution to the present day. We investigate two adjacent troughs presently near 87°N to evaluate the mass balance conditions at those sites. We constrain the contribution of insolation‐induced sublimation to the migration in the observed TMPs. We present a phenomenological model that combines our simulations of the sublimation conditions at paleo‐trough surfaces with accumulation rates to create synthetic TMPs that are tunable to the observations. Models using nominal values of lag diffusivity, albedo, and atmospheric water vapor abundance and in which the trough walls have been covered in a lag on the order of millimeters thick and formed ~2.3 Myr ago match the observed trough migration and align with expectations of trough ages. Thicker lags, and/or older troughs, would generate TMPs of constant slope, which does not match the observed paths. We demonstrate the viability of our new theoretical model for predicting conditions that lead to trough migration, allowing us to connect observable TMPs to Martian climate processes.

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Section: Methodsmentioning

confidence: 99%

A Migration Model for the Polar Spiral Troughs of Mars

et al. 2019

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“…The difference in the effective conductivity between these two schemes is a factor of up to 4–5 for our highest porosities (50%) and yields only a 2–3% change in the final ice retreat and lag thickness results. The effective conductivity of a mixture ultimately depends on how the two end‐members mix with each other; alternative effective thermal conductivity mixing models include Series (Mellon, Jakosky, & Postawko, ), Parallel (Wechsler, Glaser, & Fountain, ), Geometric Mean (Johansen, ), and Volumetric (Siegler et al, ). Experiments on icy Martian regolith analogs show that the relationship will depend on the geometry of contacts between grains (Piqueux & Christensen, ; Siegler et al, ).…”

Section: Methodsmentioning

confidence: 99%

“…The effective conductivity of a mixture ultimately depends on how the two end‐members mix with each other; alternative effective thermal conductivity mixing models include Series (Mellon, Jakosky, & Postawko, ), Parallel (Wechsler, Glaser, & Fountain, ), Geometric Mean (Johansen, ), and Volumetric (Siegler et al, ). Experiments on icy Martian regolith analogs show that the relationship will depend on the geometry of contacts between grains (Piqueux & Christensen, ; Siegler et al, ).

k = 2.1 \times 10^{- 2} + ((), 4.2 \times 10^{- 4}) ρ + ((), 2.2 \times 10^{- 9}) ρ^{3}

…”

Section: Methodsmentioning

confidence: 99%

Preservation of Midlatitude Ice Sheets on Mars

2017

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Excess ice with a minimum age of tens of millions of years is widespread in Arcadia Planitia on Mars, and a similar deposit has been found in Utopia Planitia. The conditions that led to the formation and preservation of these midlatitude ice sheets hold clues to past climate and subsurface structure on Mars. We simulate the thermal stability and retreat of buried excess ice sheets over 21 Myr of Martian orbital solutions and find that the ice sheets can be orders of magnitude older than the obliquity cycles that are typically thought to drive midlatitude ice deposition and sublimation. Retreat of this ice in the last 4 Myr could have contributed ~6% of the volume of the north polar layered deposits (NPLD) and more than 10% if the NPLD are older than 4 Myr. Matching the measured dielectric constants of the Arcadia and Utopia Planitia deposits requires ice porosities of ~25–35%. We model geothermally driven vapor migration through porous ice under Martian temperatures and find that Martian firn may be able to maintain porosity for timescales longer than we predict for retreat of the ice.

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“…This energy balance is calculated using the incident solar flux and the one-dimensional heat diffusion equation ( Delbo et al, 2015 ). The thermal properties of a regolith-ice mixture are a combination of its components ( Siegler et al, 2012 ), and are allowed to change with depth and time. The heat equation is solved with a Crank-Nicolson method with a nonlinear upper radiation boundary condition, as described in the notes distributed with the online version of the code ( Schörghofer, 2015 ).…”

Section: Thermal Modelmentioning

confidence: 99%

Measurements of thermal properties of icy Mars regolith analogs

Cited by 51 publications

References 58 publications

A Migration Model for the Polar Spiral Troughs of Mars

A Migration Model for the Polar Spiral Troughs of Mars

Preservation of Midlatitude Ice Sheets on Mars

Predictions of depth-to-ice on asteroids based on an asynchronous model of temperature, impact stirring, and ice loss

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