MARS THROUGH TIME Collectively, these observations suggest that the Noachian
to early Hesperian periods provided environmental conditions potentially favorable to prebiotic chemistry or early microbial life. Hypothetically, such life could have emerged in aqueous settings, possibly resembling cyanobacteria-like prokaryotes inhabiting shallow lacustrine or marginal marine environments (Westall et al., 2015; Grotzinger et al., 2014).
The Warm and Dry Transition: Mars During the Hesperian Period
The Hesperian Period (~3.7–3.0 Ga) represents a critical phase in
the climatic and geologic evolution of Mars, marking the transition from the relatively wetter, phyllosilicate-dominated conditions of the Noachian to the arid, sulfate-rich environments characteristic of the Amazonian (Carr and Head, 2010; Tanaka, 1986) (Fig. 14).
Figure 15. A photograph of a desert surface covered with closely packed, interlocking angular or rounded rock fragments of pebble and cobble size
that represent arid conditions in the area of the foothills of Mount Sharp in Gale Crater (NASA/JPL-Caltech/MSSS., 2022).
Figure 14. A photograph of dark material that lines the fracture walls reflects an earlier episode of fluid flow than the white, calcium-sulfate-rich veins do, although both flows occurred after the cracks formed, Mount Sharp (NASA/ JPL-Caltech/MSSS., 2014).
Each white bar in the image represents 5 cm (2 inches).
This interval is defined by widespread volcanic resurfacing, most notably in the Tharsis and Elysium regions, where extensive basaltic lava flows altered vast portions of the Martian surface (Greeley and Spudis, 1981; Tanaka, 1986). Sustained volcanic activity throughout the Hesperian contributed to ongoing crustal deformation, thermal anomalies, and tectonic restructuring (Wordsworth, 2016; Carr and Head, 2010).
Despite the overarching trend toward planetary desiccation and
dryness, geomorphological and sedimentary evidence indicates that episodic fluvial processes persisted during the Hesperian. Valley networks, deltaic deposits, and sediment-filled basins point to transient hydrological events, potentially driven by localized melting of subsurface ice, triggered by magmatic heating or short-lived climatic excursions (Howard et al., 2005; Kite et al., 2017). In particular, the Eridania Basin preserves early Hesperian deposits indicative of hydrothermal alteration, suggesting sustained interactions between volcanic and aqueous processes in a setting that may have been habitable (Bishop et al., 2018).
Simultaneously, aeolian and evaporitic processes became
increasingly dominant. Surface features such as polygonal fracture networks, desert pavements (Fig. 15), and playa-lake evaporite deposits, including halite and gypsum, suggest the presence of ephemeral water bodies subject to repeated cycles of evaporation and desiccation (El-Maarry et al., 2014). In addition, some of the craters may have hosted lakes billions of years ago when the Martian climate allowed liquid water to exist on the surface for extended periods. During the drying conditions, the water evaporates leaving mud cracks as strong evidence to support this arid environment (Fig. 16). Orbital spectroscopy (e.g., CRISM) and in situ analyses from
12 TPG •
Jan.Feb.Mar 2026
Figure 16. A photograph of a closer look at the Martian crater polygons shows cracks that strongly support drying conditions (NASA/JPL/University of Arizona, 2010).
missions such as Curiosity in Gale Crater confirm the widespread distribution of sulfate-rich stratigraphy, indicating the presence of ancient water and a shift towards acidic and increasingly arid surface conditions (Fishbaugh et al., 2007; Wordsworth, 2016).
These environmental shifts were likely driven by a combination of
factors, including a decline in atmospheric pressure and enhanced volcanic degassing of sulfur-bearing gases such as SO2. The resulting acidification of surface waters may have accelerated the geochemical transition from phyllosilicate- to sulfate-dominated weathering regimes (Carr and Head, 2010; Wordsworth, 2016). Thus, the Hesperian Period constitutes a climatically transitional epoch, bridging the warm, hydrologically active Noachian and the cold, hyper-arid Amazonian. Deciphering the spatial and temporal patterns of volcanism, hydrology, and alteration during the Hesperian remains essential for reconstructing Mars's environmental history and evaluating its potential for sustaining past microbial life.
Glacial and Interglacial Cycles during the Late Hesperian to Amazonian Periods
The transition from the Late Hesperian to Amazonian periods on Mars is marked by a significant decline in volcanic and fluvial activity,
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