New Study Identifies Potential Ancient Continental Shelf on Mars

A new research study has analyzed global topographic data from Earth and Mars, identifying a distinct, flat zone in the northern lowlands of Mars that shares characteristics with Earth's continental shelf. The study proposes this zone may represent a potential ancient landscape-to-seascape transition, based on its topography and coincidence with fluvial features.

The analysis revealed a distinct, flat zone on Mars with an elevation range of -1,800 to -3,800 meters, which spatially coincides with numerous ancient fluvial features and proposed shorelines.

Study Methodology and Data Sources

The research utilized three primary datasets to enable a direct comparison between Earth and Martian landscapes.

1. Global Topographic Data

• Earth: The ETOPO1 Global Relief Model was selected for its uniform 1 arcmin resolution across both land and ocean surfaces.
• Mars: Topography from the Mars Orbiter Laser Altimeter (MOLA) was used, with a native resolution of 463 meters per pixel.
• Both datasets were resampled to 2.5 km, 5 km, and 10 km resolutions to facilitate uniform analysis and focus on broader-scale features.

2. Maps of Fluvial and Oceanic Features

• Earth: Researchers incorporated maps of major global rivers, deltas, and seafloor geomorphic features, including the continental shelf, slope, rise, abyssal plain, and hadal zone.
• Mars: Mapped features included valley networks, outlet canyons, fluvial ridges, interpreted deltas, and two proposed ancient shorelines known as the Arabia and Deuteronilus shorelines. From available datasets, 48 Martian deltas were selected based on criteria including open downstream flow and complex stacking patterns.

3. Terrain Analysis

• Elevation, slope, and curvature were calculated for raster cells on both planets.
• The landscape classification tool 'Geomorphons' was applied to map potential transition zones. Different flat-terrain angle thresholds were used for each planet: 1.22° for Earth and 0.31° for Mars.

Key Findings on Mars

The analysis focused on the Martian northern lowlands and yielded several specific results:

• A distinct intermediate-elevation zone was identified with an elevation range of -1,800 meters to -3,800 meters. At a 5 km resolution, this zone has a median slope of 0.31°.
• This zone spatially coincides with numerous geomorphic indicators, including deltaic systems, valley network termini, fluvial ridges, and the proposed Arabia and Deuteronilus shorelines.
• Statistical analysis using the Kruskal–Wallis H test showed a significant difference in slope distributions between three elevation bands: above -1,800 m, between -1,800 m and -3,800 m, and below -3,800 m. This indicates the populations are statistically distinct.
• The study reports that applying the 0.31° flat angle threshold with the Geomorphons tool detected a surface on Mars. When combined with topographic analysis and morphological features, this surface was spatially constrained to the -1,800 m to -3,800 m zone.

Proposed Interpretation and Limitations

Based on the analysis, the researchers propose that the detected flat surface in the Martian northern lowlands may correspond to a potential ancient continental shelf-like feature.

The study notes several limitations and sources of uncertainty:

• Topographic Alteration: Potential reshaping of Mars' topography from true polar wander and the emplacement of the Tharsis volcanic province.
• Isostatic Response: Uncertainty from crustal rebound in response to the unloading of a potential ocean, though estimated rebound for Mars is suggested to be smaller than the ~2 km elevation span of the detected zone.
• Surface Processes: Effects of long-term burial, exhumation, and erosion over Martian history.
• Flood Erosion: Erosion and sediment redistribution by Hesperian-aged outflow floods, which are noted as a probable contributor to surface flattening in some areas, such as Chryse Planitia, but are not considered the primary cause across the broader northern lowlands.