Polar Deposits of Mars

Thomas, Paul J.; Squyres, S. W.; Herkenhoff, K. E.; Howard, Abby; Murray, Bruce C.

doi:10.2307/j.ctt207g59v.27

Cited by 109 publications

(241 citation statements)

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“…With albedo A = 0.43 (Thomas et al 1992), the emissivity ε taken as unity and the present insolation I in np (0) = 79.96 W m −2 , we obtain the present temperature T np (0) = 168.4 K. The temperature history, which varies by ca. 30 K within the considered range of obliquities, is depicted in Fig.…”

Section: Surface Temperaturementioning

confidence: 99%

“…The seasonal caps, which can extend down to latitudes of approximately 55 • N/S, consist of only some ten centimeters of CO 2 snow which sublimes into the atmosphere during the respective spring season. The smaller residual caps poleward of approximately 80 • N/S are underlain by massive topographic structures known as the polar layered deposits (Thomas et al 1992). The complexes composed of the residual caps and the layered deposits are referred to as the north-and south-polar cap (NPC/SPC), respectively (e.g., Johnson et al 2000, Byrne and Murray 2002, Greve et al 2003.…”

Section: Introductionmentioning

confidence: 99%

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Evolution of the north-polar cap of Mars: a modelling study

Greve

Mahajan

Segschneider

et al. 2004

Planetary and Space Science

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Celestial-mechanical computations show that, even stronger than for Earth, Mars is subject to Milanković cycles, that is, quasi-periodic variations of the orbital parameters obliquity, eccentricity and precession. Consequently, solar insolation varies on time-scales of 10 4 -10 5 years. It has long been supposed that this entails climatic cycles like the terrestrial glacialinterglacial cycles. This hypothesis is supported by the light-dark layered deposits of the north-and south-polar caps indicating a strongly varying dust content of the ice due to varying climate conditions in the past. This study aims at simulating the dynamic and thermodynamic evolution of the north-polar cap (NPC) of Mars with the ice-sheet model SICOPOLIS. The boundary conditions of surface accumulation, ablation and temperature are derived directly from the solar-insolation history by applying the newly developed Mars Atmosphere-Ice Coupler MAIC. We consider steady-state scenarios under present climate conditions as well as transient scenarios over climatic cycles. It is found that the NPC is most likely not in steady state with the present climate. The topography of the NPC is mainly controlled by the history of the surface mass balance. Ice flow, which is of the order of 1 mm a −1 , plays only a minor role. In order to build up the present cap during the last five million years of relatively low obliquities, a present accumulation rate of ≥ 0.25 mm water equiv. a −1 is required. Computed basal temperatures are far below pressure melting for all simulations and all times.

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Section: Surface Temperaturementioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Evolution of the north-polar cap of Mars: a modelling study

Greve

Mahajan

Segschneider

et al. 2004

Planetary and Space Science

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“…The different albedo of the layers are interpreted to be caused by variable proportions of dust and water ice [Thomas et al, 1992], the result of cyclical variations in the orbit and rotation of Mars that affected insolation, and thus water ice and dust deposition and removal rates at the poles [Laskar et al, 2002].…”

Section: Introductionmentioning

confidence: 99%

Permittivity estimation of layers beneath the northern polar layered deposits, Mars

Lauro

Mattei

Pettinelli

et al. 2010

Geophysical Research Letters

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Martian Polar Layered Deposits, most likely dusty ice\ud are transparent to radar waves. In the North Pole bedrock\ud has been detected by MARSIS up to a depth about 2 Km,\ud whereas in the South Pole such interface has been located\ud at about 3.7 Km. The reflected signal is generally above\ud the noise and can be used to estimate the dielectric properties\ud of the bedrock. Assuming the permittivity of the first layer is\ud known, we use a simplified inversion method to extract the\ud bedrock relative dielectric permittivity as 4–9 below the\ud North PLD’s. These values are coherent with the basalt\ud nature and so the approach could be used to identify the\ud lithology beneath the Martian Poles

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“…Thus the presence of Chasma Boreale appears to have influenced the orientation of the troughs. This observation suggests either that these troughs are younger than Chasma Boreale as noted by Thomas et al [1992] or that they share a genetic connection.…”

Section: Comparison To Polar Troughsmentioning

confidence: 78%

“…Effects of these winds grow stronger as they approach the edge of the glacier [Benn and Evans, 1998]. Zuber et al [1998] find that the orientation of Chasma Boreale, the steep slopes of the chasma walls and the outlying mesa, and the lack of a monotonically decreasing floor slope suggest that the cap once Thomas et al [1992]. extended out to the mesa and was eroded back by eolian processes, forming Chasma Boreale.…”

Section: Accublation Model [42]mentioning

confidence: 99%

Chasma Boreale, Mars: Topographic characterization from Mars Orbiter Laser Altimeter data and implications for mechanisms of formation

Fishbaugh

2002

J. Geophys. Res.

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[1] Chasma Boreale, a large reentrant in the north polar cap of Mars, is distinct in scale, detailed topography, and orientation from the spiraling troughs that characterize the majority of the polar cap. We use new, high-resolution Mars Orbiter Laser Altimeter (MOLA) data and Mars Orbiter Camera (MOC) and Viking images of the chasma region to assess hypotheses of origin of Chasma Boreale. These hypotheses include formation by glacial flow and ablation, by eolian processes (such as katabatic winds) and sublimation, by outflow of meltwater, or by a combination of two or more of these processes. We find that these new data support initial formation by outflow of meltwater with later modification by katabatic winds and sublimation. On the basis of our analysis we suggest a possible scenario in which outflow has occurred in several stages. The outflow appears to have begun near an enclosed depression at the head of the chasma; meltwater migrated within and below the ice down the regional slope and eventually broke out to the surface. Removal of material by melting caused subsidence and erosion of the polar deposits forming the chasma, which has subsequently undergone modification by eolian and sublimation processes. The outflow deposited most of its sediment in the form of a lobe that stratigraphically overlies the polygonal plains mapped at the mouth of the chasma and scoured some of the circumpolar sediment mantle in the surrounding region. The lowest portions of the North Polar Basin received the rest of the sediment as a deposit a few meters thick. MOLA data also reveal evidence for similar events of smaller magnitude elsewhere on the margins of the polar cap.

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Polar Deposits of Mars

Cited by 109 publications

References 0 publications

Evolution of the north-polar cap of Mars: a modelling study

Evolution of the north-polar cap of Mars: a modelling study

Permittivity estimation of layers beneath the northern polar layered deposits, Mars

Chasma Boreale, Mars: Topographic characterization from Mars Orbiter Laser Altimeter data and implications for mechanisms of formation

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