Grid Mapping the Northern Plains of Mars: Using Morphotype and Distribution of Ice‐Related Landforms to Understand Multiple Ice‐Rich Deposits in Utopia Planitia

Abstract

This work in Utopia Planitia is the first continuous regional mapping of ice‐related landforms integrated into an effort to study the three main basins (Arcadia, Acidalia, and Utopia Planitiae) in the northern plains. The distribution and morphotypes of these landforms, SHAllow RADar detections, and crater size‐frequency distribution measurements (>50 m in diameter) were used to understand the permafrost cryolithology and its past evolution in relation to climate in Utopia Planitia. Three assemblages of landforms were identified based on their spatial correlation and correlation with Mars Orbiter Laser Altimeter surface roughness along a strip from 30°N to 80°N. At 30°–38°N, the assemblage is formed by kilometer‐scale polygons, high‐albedo mounds, and thumbprint terrains. This assemblage is associated with a lobate deposit of 30 m in thickness with a crater retention age of 1 Ga. At 38°–47°N, the assemblage is comprised of large scallops, 100‐m‐diameter polygons, pits, and mantled deposits. This assemblage is correlated with a deposit of 80 m in thickness containing excess ice (~50–85% by volume) with a crater retention age of about 10 Ma. At 47°–78°N, the assemblage is composed of mantled deposits, textured terrains, and 30‐m‐diameter polygons. This assemblage is related to the ice‐rich, debris‐covered, latitude‐dependent mantle that has a crater retention age of about 1.5 Ma. Utopia Planitia appears to be a region of combined depositions of sediment and continuous cold climatic conditions that leaded to a complex distribution of ground ice.

Grid Mapping the Northern Plains of Mars: Geomorphological, Radar, and Water‐Equivalent Hydrogen Results From Arcadia Plantia

“…Widespread pitting supports the idea that the LDM has at least in the past contained volatiles (e.g., Kostama et al, ; Kreslavsky & Head, ; Mustard et al, ) and has been subjected to subsequent volatile loss between 35 and 75°N. Scalloped pits are found between 50 and 55°N but are much less pervasive than in Utopia Planitia (Séjourné et al, ). The degradation of the LDM appears to grade from less severe in the north to more severe in the south, with pitting becoming more widespread and more bedrock being observable in the south.…”

“…These northern polygons are reminiscent of frost‐filled thermal contraction cracks, but again, their morphology is often unclear. What is clear, however, is that there are many fewer 100‐m‐scale polygons visible in Arcadia than smaller polygonally patterned grounds (seen as part of the textured category) and far fewer than mapped in the Acidalia and Utopia areas (Orgel et al, ; Séjourné et al, ).…”

Grid Mapping the Northern Plains of Mars: A New Overview of Recent Water‐ and Ice‐Related Landforms in Acidalia Planitia

“…LDM and textured terrain occur ubiquitously from 44°N to 78°N in Acidalia Planitia further north than in Arcadia and Utopia Planitiae (Ramsdale et al, , Séjourné et al, ). The origin of ice by air fall deposition is most likely, as LDM and its degraded varieties are draped over the terrain regardless of topography and are uncorrelated with geologic boundaries, outflow channels, or tectonic features, as would be expected if the ice had a fluvial or groundwater origin.…”

“…Overview map of the three main basins of the northern lowlands: Acidalia (this study), Utopia (Séjourné et al, ), and Arcadia Planitiae (Ramsdale et al, ).…”

“…In Acidalia Planitia, scalloped terrain can only be found within a limited latitude range between 46°N and 57°N and is mostly concentrated in the Acidalia Colles region (48–53°N; Figures b and d). All observed isolated scalloped depressions in Acidalia Planitia are characterized by a diameter of <100 m and are less prominent features than in Utopia Planitia (Morgenstern et al, , Séjourné et al, , Séjourné et al, ). Scalloped terrain cooccurs with the LDM and textured terrain but is surprisingly less correlated with the small‐scale polygons.…”