Sculpting of Martian brain terrain reveals the drying of ancient Mars

TL;DR

This study combines morphological analysis and numerical modeling to reveal that Martian brain terrain formed through initial freeze-thaw processes followed by sublimation-driven sculpting, indicating a climate shift from wet to dry on Mars.

Contribution

It introduces a quantitative system and a numerical model to explain MBT formation, highlighting the role of sublimation in shaping Martian terrain.

Findings

Self-organized transport alone cannot produce the observed relief of MBT.

Sublimation-driven sculpting accounts for the majority of relief features.

MBT formation involved a transition from liquid water processes to dry sublimation effects.

Abstract

The Martian brain terrain (MBT), characterized by its unique brain-like morphology, is a potential geological archive for finding hints of paleoclimatic conditions during its formation period. The morphological similarity of MBT to self-organized patterned ground on Earth suggests a shared formation mechanism. However, the lack of quantitative descriptions and robust physical modeling of self-organized stone transport jointly limits the study of the thermal and aqueous conditions governing MBT's formation. Here we established a specialized quantitative system for extracting the morphological features of MBT, taking a typical region located in the northern Arabia Terra as an example, and then employed a numerical model to investigate its formation mechanisms. Our simulation results accurately replicate the observed morphology of MBT, matching its key geometric metrics with deviations <15%. Crucially, however, we find that the self-organized transport can solely produce relief <0.5 m, insufficient to explain the formation of MBT with average relief of 3.29 \pm 0.65 m. We attribute this discrepancy to sculpting driven by late-stage sublimation, constraining cumulative subsurface ice loss in this region to ~3 meters over the past ~3 Ma. These findings demonstrate that MBT's formation is a multi-stage process: initial patterning driven by freeze-thaw cycles implying liquid water followed by vertical sculpting via sublimation requiring a dry environment. This evolution provides physical evidence for the transition of the ancient Martian climate from a wetter period to a colder hyper-arid state.