Surface Roughness Evolution and Implications for the Age of the North Polar Residual Cap of Mars

Abstract

The North Polar-Layered Deposits (NPLD), together with the overlying North Polar Residual Cap (NPRC), represent one of the largest, most conspicuous water-ice reservoirs on Mars, and in the inner solar system. The NPLD are made up of vertically stratified layers of predominantly water-ice with a varying fraction of dust incorporated within each layer (Figure 1). NPLD stratigraphy has been observed via numerous exposures across the cap, often where erosional scarps reveal 1D columns of layers (Byrne, 2009). These layers are thought to represent periods of net accumulation or ablation of ice and dust predominately controlled by changes in insolation over time (Cutts & Lewis, 1982; Laskar et al., 2004). Insolation at different latitudes has changed over time due to Mars' varying orbital parameters: obliquity, eccentricity, and longitude of perihelion (Laskar et al., 2004). If this is the mechanism controlling layer formation within the NPLD, its stratigraphy should record a signal of past orbital and climate conditions, very similar to ice-cores taken from terrestrial ice sheets (Hvidberg et al., 2012). Before this climate record can be interpreted, however, the processes responsible for shaping layers within the NPLD must be better constrained. As NPLD layers are former surfaces, understanding their formation requires knowledge of the processes that shape the NPLD surface today. The NPRC, which covers most of the NPLD, is considered to be the topmost layer of the NPLD (Tanaka, 2005

Geologic Context of the Bright MARSIS Reflectors in Ultimi Scopuli, South Polar Layered Deposits, Mars

“…NPLD surface features have been suggested to form in a way related to snow sedimentation on Earth (e.g., megadunes, referred to as “sastrugi” in Herny et al., 2014). On the NPLD, linear surface textures may be explained by differences in surface illumination and therefore, temperature and accumulation due to vapor diffusion with time (e.g., Wilcoski & Hayne, 2020). The model of Wilcoski and Hayne (2020) suggests that ∼10 m wavelength features form on kyr timescales.…”

“…On the NPLD, linear surface textures may be explained by differences in surface illumination, and therefore temperature and accumulation due to vapor diffusion with time (e.g., Wilcoski & Hayne, 2020). The model of Wilcoski and Hayne (2020) suggests that ~10 m wavelength features form on kyr time scales. Our measured feature wavelengths of 100s of meters suggests a significantly longer time to develop these features.…”

Modern Mars' geomorphological activity, driven by wind, frost, and gravity

“…However, modeling by Wilcoski and Hayne (2020) indicates that hummocks would form in both ablational and depositional settings and, further, that hummock wavelength correlates primarily with age regardless of net ablation or deposition; they find that the typically observed ~10 m hummock wavelengths are reached after ~1 kyr. This timescale is consistent with ~1.5 kyr ages derived from cratering statistics (Landis et al, 2016).…”

Polar Ice Accumulation from Volcanically Induced Transient Atmospheres on the Moon

“…Therefore, the maximum temperature of a region determines the stability of ice in that region (Watson et al 1961;Paige et al 2010b). We can calculate the rate of ice accumulation in a region with maximum temperature T max by considering a laminar air layer at the surface through which water vapor can diffuse and above which the atmosphere is well mixed (Wallace & Sagan 1979;Bapst et al 2018;Wilcoski & Hayne 2020). The efficiency of water vapor transport between the atmosphere and the surface will be limited by the thickness d of the laminar layer and the molecular diffusivity D of H 2 O through the CO-dominated laminar layer.…”

“…The ice accumulation model is based on previous work that has considered water ice accumulation/ablation on Mars (Wallace & Sagan 1979;Bapst et al 2018;Wilcoski & Hayne 2020); fundamental physical similarities motivate its application to the transient paleo-atmospheres of the Moon. In this model, the wind speed above the surface increases logarithmically and causes the atmosphere above the surface to be divided into two layers.…”